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Pathogenesis and management of male infertility
Rev
iew
acticle
Pathogenesis and management of male infertility
Recent research has brought good news for infertile couples inasmuch as there are new treatment strategies, such as in-vitro fertilisation (IVF) and microinsemination. The bad news, however, is that this progress is restricted mainly to treatment of symptoms; there has been little gain in prevention and clarification of the underlying causes. Here we focus on male infertility, which has received little attention both scientifically and in medical practice. About 15% of all couples will experience primary or secondary infertility at some time during their reproductive lives.1,2 In about half these cases, there is a contributing male factor. However, the distinction between a man with normal fertility and one with reduced fertility may be difficult. According to the WHO classification, a human semen specimen is normal even if up to 70% of the spermatozoa have abnormal morphology (figure l)-a much higher percentage than in most other mammals. A high number of abnormal sperm heads is associated with decreased fertilisation capacity in animals and in human beings.3 Furthermore, the moderately high number of spermatozoa with abnormal heads in otherwise normal men in the industrialised world could reflect a general health
including prolactinoma, craniopharyngioma, other brain tumours, or radiation treatment. Although patients with gonadotropin insufficiency occasionally present via infertility clinics, the frequency of this disorder in infertility is small (ie, less than 0-5%).
problem. An important point is that male infertility is not an entity but reflects a variety of different pathogenetic mechanisms. shall review the causes from a functional viewpoint (panel), and our description will not be weighted according to prevalence. Rather, the focus will be on aspects of male infertility for which recent research has revealed new information. Thus
we
Causes of male
Infertility
Impaired sperm production and function Hypothalamic pituitary disorders A primary lesion in the pituitary gland or hypothalamus may secondarily lead to hypogonadism. The congenital form of hypogonadotropic hypogonadism (Kallmann’s syndrome) is due to a deficiency of gonadotropin-releasing hormone (GnRH). There is a large excess of men. Recently a deletion of a single gene, Kalig-2, has been found in the X-linked form of the disease.4 This gene encodes for certain neurons that migrate during fetal life, including those involved in the production of GnRH. The lack of gonadotropic hormones before and after birth seems to explain the frequently observed testicular maldescent as well as the absence of pubertal development. The acquired form of hypogonadotropic hypogonadism is most often due to pituitary adenomas University Department of Growth and Reproduction, Rigshospitalet, DK-2100 Copenhagen, Denmark (Prof N E Skakkebæk MD, A Giwercman MD); and Institute of Reproduction and Development, Monash University, Monash Medical Centre, Victoria, Australia (Prof D de Kretser MD) Correspondence to: Prof Niels
E Skakkebæk
Figure
1: Smears of semen
samples of (a) healthy man and (b)
bullI Note that high proportion of human spermatozoa is abnormally shaped with enlarged irregular heads. By contrast, bull spermatozoa are all normal with regular heads.
Genetic factors
including chromosome abnormalities The 47,XXY karyotype (Klinefelter’s syndrome) and its variants are almost always associated with azoospermia. Although the cause of testicular failure is clear, the pathogenesis is unknown. It is interesting that the extra X chromosome apparently causes little effect on the structure of the seminiferous tubule before puberty when an overwhelming destruction of the seminiferous epithelium takes place. Some patients with Klinefelter’s syndrome do, in fact, have significant growth of the testes early in puberty followed by a subsequent enormous shrinkage of the testes resulting in the well-known adult phenotype with microtestis. Men with an extra Y chromosome have various degrees of spermatogenic impairment, ranging from normal spermatogenesis to spermatogenic arrest and the Sertolicell-only pattern. Autosomal chromosome rearrangements including translocation may also result in reduced fertility, 1473
testicular biopsy samples of the contralateral testis in men with unilateral testicular cancer, severe impairment of spermatogenesis was present in 25% of the cases, including Sertoli-cell-only pattern, spermatogenic arrest, and carcinoma-in-situ.9 Semen quality at the time of diagnosis of the unilateral testicular cancer is also substantially impaired. Testicular cancer has its origin in carcinoma-insitu cells which even in adult men express fetal antigens and may be of fetal origin.10,11
Panel: Known causes of male Infertility Mechanism Absent testicular
Cause/pathogenesis Anorchia Bilateral castration
tissue
Impaired sperm production or
Hypogonadotropic hypogonadism ,
function
Klinefetter’s syndrome variants 47.XXY mates; 46,XX males Partial androgen insensitivity Autosomal rearrangements AZF-gene deletions
Germ-cell aplasia In many men with azoospermia, the seminiferous tubules contain only Sertoli cells. This cytological appearance can result from numerous causes, such as cryptorchidism, cytotoxic drugs, or irradiation (see below). However, in many cases the aetiology is unknown. The absence of germ cells may be due to factors present during fetal life. Furthermore, a subtle Leydig-cell insufficiency may be associated with Sertoli-cell-only
Spermatocytic arrest Cryptorchidism Cancer of testis Varicocele
Sertoli-celt-oniy Irradiation
Cytotoxic drugs Other drugs Environmental agents
.
.
Impaired sperm transport
Autoimmune infertility Epididymai blockage of vas deferens and other parts in seminal pathways
Ejaculatory failure Previous vasectomy
Impotence Kartagener’s syndrome Disturbances in sperm-oocyte fusion
Abnormal egg-binding proteins
Recurrent
Chromosomal aberrations
miscarriage is heterogeneous. For unknown reasons autosomal translocations may result in more severe impairment of fertility in the male than in the female. Chromosome abnormalities that give rise to unbalanced gametes may also be associated with repeated abortions. The arrest of spermatogenesis may, in rare cases, be due to impaired chromosome pairing in meiosis, resulting in azoospermia. A high proportion of parental consanguinity indicates that the disorder may be caused by a recessive mutation. Recently a genetic region controlling spermatogenesis in human beings-human azoospermia factor (AZF)-has been localised to the long arm of the Y chromosome,S and disturbed spermatogenesis and azoospermia have been recorded in men with deletions corresponding to the AZF region.6 However, the quantitative role of genetic abnormalities in men with unexplained spermatogenic disorders remains unclear.
although the pattern
Undescended testis The undescended testis is associated impaired spermatogenesis, although the extent of impairment may vary from a complete Sertoli-cell-only pattern to only a slight reduction in the number of germ cells.7 The fact that spermatogenesis is also impaired in the contralateral testis in patients with unilateral maldescent seems to indicate that some patients with maldescent have a congenital defect of the germ-cell population. Some investigators believe that the suprascrotal position of the testes in childhood causes the further decrease in the number of germ cells. Therefore, early treatment of cryptorchidism (before age 1 or 2) has been advocated. Data from the UK suggest that the rate of cryptorchidism is with
increasing.8 Testicular cancer Testicular cancer is associated with increased risk of impaired spermatogenesis. In a study 1474
an on
syndrome. Drugs It is striking that we know so little about the effects on fertility of commonly used drugs. In most countries the testing of drugs does include toxicity studies of the reproductive organs in animals. The safety checks in clinical trials generally do not include tests to elucidate the function and impairment of the human gonad. Impaired semen quality has been detected by chance during the use of drugs that were given routinely before their toxic effect was known. For example, sulphasalazine, which is used to treat inflammatory bowel diseases, can drastically reduce semen quality. Although the effects seem to be reversible when this drug is used in moderate doses for a limited time, the production of spermatozoa may be permanently impaired. Some antihypertensive drugs (eg, 0-blockers) may cause impotence. Anabolic steroids, which are widely used by athletes and body-builders, have severe side-effects on reproduction including oligozoospermia and azoospermia. The numerous cytotoxic drugs that are used to treat cancer and autoimmune disease are potentially damaging for gonadal function-especially the alkylating agents (eg, cyclophosphamide, procarbazine, cisplatin), which cause gonadal failure. However, there may be striking differences between the effects of the same drug on men and women. 12
Environmental factors Several environmental toxicants known to impair reproductive function have been identified in the workplace during the past 15 years. In addition to the chlorinated nematocide dibromochloropropane (DBCP) and chlordecone, there is strong evidence of spermatotoxic effects of other pesticides, such as carbaryl and ethylenedibromide, of some glycol ethers (with widespread use in paintings, printing inks, and adhesives), and of the metals lead, cadmium, and mercury. Male metal welders may be at increased risk of subfecundity, although the nature of the harmful exposures remains to be identified.13 From limited data it appears that the human seminiferous epithelium is more vulnerable to toxicants than is the testis of other animals. The reproductive system is especially vulnerable during development. Therefore, it is important to study possible environmental effects on reproduction in more than one generation. Work with laboratory animals has shown that irradiation of a pregnant female can cause total depletion of fetal germ cells without otherwise affecting the fetus or the mother. Thus, in the search for environmental factors affecting reproduction the focus should perhaps be more on the role of environmental agents on the fetus. Recently, the oestrogenic effect of several
environmental toxins has attracted attention as a possible cause of defects in the male reproductive organs.ll Nutrition and socioeconomic factors may also be important. The hypothalamic-GnRH pulse generator, which controls gonadal function, is affected by several hormonal, metabolic, and neural signals. Therefore, stress, undernutrition, socioeconomic problems, emotional deprivation, and drugs may all affect the onset and maintenance of reproductive function.14 Several life-style factors may have consequences for reproduction, including diet, clothing, exercise, and the use of alcohol, tobacco, and recreational drugs (eg, marijuana). Little is known about the effects of these factors on semen quality and therefore on male fertility potential. Varicocele This condition is present in 25-40% of men attending infertility clinics compared with about 10-15 % of men in the general population. The pathogenesis of spermatogenic failure in men with varicocele is largely unknown. One suggestion is that this failure is due to increased temperature, accumulation of CO2, and other noxious substances (including adrenal steroids and catecholamines) brought on by the venous reflux.ls However, the role of varicocele in infertility, especially with respect to its management, is controversial (see below).
Impaired sperm transport Autoimmune infertility The testis is an immunologically privileged site and spermatozoal antigens are effectively shielded from being recognised by the cells of the immune system. However, an autoimmune reaction against the spermatoza is seen in 5-10% of men being treated for infertility as an isolated abnormality. Circulating sperm antibodies are present in most men who have undergone vasectomy, and after reversal of the procedure these antibodies often appear in the seminal plasma. Unilateral or bilateral obstruction of the genital tract (either congenital or acquired), for reasons other than vasectomy, may also be associated with an autoimmune response against spermatozoa. In addition, epididymitis and varicocele may be associated with sperm antibodies. The most extensive studies on the importance of the immunoresponse for fertility have been done on men who have undergone vasectomy reversal. When there is a close association between the presence of antibodies and fertility potential, IgA in the semen appears to have a more important role than does IgG.16
Other
Sexually transmitted diseases may cause and lead to blockage of the ductal system, epididymitis in resulting permanent azoospermia. Obstructive azoospermia can also be due to agenesis of the epididymis and other parts of the ductal system including the vas deferens. Some of these cases seem to be of genetic origin. Congenital bilateral agenesis of the vas deferens is found in most patients with cystic fibrosis. Recently it has been shown that point mutations of the cystic fibrosis gene may causes
be present in at least two-thirds of men with isolated bilateral agenesis of the vas deferens without any other symptoms of cystic fibrosis." This finding has practical implications for the management (with assistedreproduction technology) of azoospermic men with preserved spermatogenesis and agenesis of the vas deferens, since genetic counselling may be indicated. Anejaculation or retrograde ejaculation may occur in diabetic patients as well as after retroperitoneal lymph-node dissection, spinal cord injury, and bladder-neck surgery. Other types of
sexual
dysfunction (including impotence) are, however, of infertility. Once the spermatozoa have been into the female tract, their motility depends on ejaculated their forward motion. Patients with the rare Kartagener’s syndrome (immotile cilia syndrome) are unable to produce motile spermatozoa owing to missing dynein arms. rare causes
Disturbances in sperm-oocyte fusion Studies in laboratory animals and man have shown that complementary adhesion molecules are located on the surface of oocytes and spermatozoa.18,19 These molecules interact and lead to fusion of the gametes (fertilisation). In the zona pellucida, two proteins called ZP2 and ZP3 seem to be especially involved in the adhesion of the spermatozoan to the oocyte. sp56 and (pro)acrosin are possible complementary egg-binding proteins on the spermatozoa. The function of this system seems important not only for fusion but also for prevention of polyspermy. Abnormalities in the adhesion molecules on the gamete surface may potentially contribute to infertility, although the clinical significance of these molecules have not been documented. Reactive oxygen species generated by leucocytes or the spermatozoa themselves may also have a role in sperm-oocyte fusion .20
Unexplained infertility In about 15%of couples who seek help no apparent cause can be found: semen quality fulfils the criteria for normalcy, and no defect in the woman’s reproductive system can be found. It is common to use the term unexplained infertility for such cases .20 However, different laboratories use different methods of investigation, and a man with unexplained infertility may obtain a diagnosis if he is seen at another clinic. Furthermore, a classification of a semen sample as normal does not necessarily mean that the specimen has the capacity to fertilise. Neither conventional semen analysis nor modern sperm function tests can reveal the exact fertilising capacity of a particular semen sample; they may indicate fertility potential and nothing more. Introduction of new methods of assessment of sperm function (eg, measurement of reactive oxygen species2O) may move more and more cases of unexplained infertility into categories of well-defined causes. Couples with unexplained infertility often shown fertilisation failure during IVF despite apparently normal gametes.
Management of the Infertile male Introduction of new assisted-reproduction techniques has moved the interest of many infertility clinics from the man as a whole to his semen and its usefulness for assisted fertilisation. Nonetheless, it is essential that the male partner is thoroughly investigated to clarify whether any of the potentially curable causes of infertility is present. It is important to emphasise that careful clinical examination may give important information, which in some cases-eg, Klinefelter’s syndrome, Kallmann’s syndrome, varicocele, or cryptorchidism-may be sufficient to establish the cause of infertility with a high degree of certainty.
Investigations Semen analysis
In view of the substantial variability of men, at least 2-3 analyses, including evaluation of volume, sperm concentration, motility, and morphology, should be done.21 The presence of sperm sperm counts
in
some
1475
antibodies,
can
easily be detected by the immunobead
or
mixed antiglobulin reaction tests which localise IgG or IgA to specific regions of spermatozoa. Functional impairment caused by antibodies is evaluated by the sperm mucuspenetration test, which assesses the capacity of spermatozoa to move through a column of mid-cycle cervical mucus. Up to 1 million leucocytes per mL of semen is regarded as normal (peroxidase staining technique). However, the use of monoclonal antibodies to specific leucocytes questions the validity of these data.22 The relation between leucocyte count and the presence of genital tract inflammation still requires confirmation. Accessory gland function can be assessed by measurement of seminal fructose (seminal vesicles) and acid phosphatase, zinc, or citrate (prostate). Their concentrations can be low in the presence of prostatitis or vesiculitis, but a normal value does not exclude the presence of infection. An acid pH and low fructose concentrations can indicate absence of seminal vesicles and the vas deferens. Post-ejaculatory urine should be investigated for presence of spermatozoa if retrograde ejaculation is suspected.
New tests of sperm function The poor prediction of fertilising capacity by routine semen analysis has led to new tests of sperm function; of these, the strict morphology evaluations, acrosomal assessment, and sperm-zona binding have provided the best assessments.23,24 The tests of human sperm/zona-pellucida interactions are done with oocytes that can be used fresh or after storage in concentrated salt solutions. Since these zonae and oocytes represent a heterogeneous population, it is important that control and test spermatozoa are used. In-vitro studies suggest that sperm-zona binding ratios and the proportion of zonae penetrated by spermatozoa give a powerful prediction of fertilisation in IVF.24 The production of reactive oxygen species by sperm from infertile men is significantly raised and correlates with their capacity for fertilisation.2s It has been proposed that these reactive oxygen species cause lipid peroxidation in sperm membranes and thereby interfere with their ability to react in the membrane fusion events that are associated with fertilisation. Measurement of reactive oxygen species production is easy, but further studies on larger populations of patients are needed to see whether the encouraging results on fertilising ability are confirmed. Endocrine evaluation
Although gonadotropin deficiency is uncommon, diagnosis of hypogonadotropic hypogonadism is important since treatment is available. The measurement of serum follicle-stimulating hormone (FSH) is generally regarded as valuable to distinguish patients with azoospermia who have obstruction (normal FSH) from those who have seminiferous tubule destruction (raised FSH). However, recent data indicate that in azoospermic men an
obstruction
cannot
be excluded
even
if FSH is
substantially raised provided that at least one of the testes is of normal size. In 30% of men with severe oligozoospermia or azoospermia resulting from severe damage to the seminiferous epithelium, leutinising hormone concentrations are high and testosterone concentrations are low.26
Chromosomal and genetic studies These are most valuable in patients with azoospermia, high FSH, and small testes (2-6 mL), with the diagnosis of Klinefelter’s syndrome (47,XXY) being made in up to 20% of some series. Screening for the cystic fibrosis gene is required in patients with congenital absence of the vas deferens.27 1476
biopsy Testicular biopsy can confirm the diagnosis of obstructive azoospermia (normal testis size associated with azoospermia). At varicocele surgery, a biopsy can be done to assess the state of the seminiferous epithelium and provide prognostic information to the patient. An additional benefit for the infertile man is the possibility of disclosing carcinoma-in-situ. The risk of early testicular malignant disease (carcinoma-in-situ) may be increased in infertile men, especially those with a history of cryptorchidism.28 Testicular ultrasonography This procedure can locate impalpable testes or those accompanied by a hydrocele and Testicular
also facilitate the detection of cysts or other abnormalities in the scrotum. Rectal ultrasound examination can also be used to assess prostate and seminal vesicle size and to diagnose ejaculatory duct obstruction. The latter is being recognised more commonly as a cause of obstructive azoospermia or severe oligozoospermia, and surgical intervention can improve fertility.29
Therapeutic approach In general, specific causes of male infertility should be sought and treated but when no cause is found, use of assisted-reproduction technology is the only option for the management of men with subfertile semen. Patients with obstructive azoospermia should be offered epididymovasostomy with microsurgical techniques, but the success of this procedure is dependent on the site of the obstruction. Low epididymal lesions are more successfully treated than high lesions since the size of the epididymal duct increases in the caudal region and in low lesions there is a greater length of epididymal duct for the process of epididymal sperm maturation. 30 In western societies, vasectomy reversal is frequently requested. The presence of sperm antibodies may complicate obstructive lesions and may be the reason for failure to achieve a pregnancy after technically successful reversal. In cases of failed reversal, in patients who decide not to proceed with surgery, or in patients with congenital absence of the vas deferens, surgical aspiration of spermatozoa from the epididymis for use in assisted reproduction is feasible.31,32 For obstruction at the level of the ejaculatory duct, recent data report encouraging results after panendoscopy and excision of the region of the prostatic urethra into which the ejaculatory ducts drain.29 The management of patients with a varicocele is contentious.33 Despite increasing evidence that varicocele does influence sperm production,34 there have been no properly controlled trials of varicocele ligation. In general, a long duration of infertility (2 years), a low sperm count, and a normal FSH would be reasons to undertake varicocele ligation. Raised FSH in association with severe oligozoospermia usually indicates testicular damage that is unlikely to recover from varicocele ligation. More recently, the successful radiological occlusion of spermatic veins by the installation of acrylamide glues or coils has been reported.35 Such an approach, however, requires excellent radiological intervention techniques. If genital tract infection is diagnosed, treatment with broad-spectrum antibiotics, such as trimethoprim,
erythromycin, and doxycycline, which gain access to the accessory glands should be given. Advice about the frequency of ejaculation to facilitate drainage of the accessory glands is also of value. Patients with anti-sperm antibodies as the cause of infertility may be offered prednisolone therapy, continuously or intermittently. This
showed that men with single defects (an abnormal count, motility, or morphology) achieved a fertilisation rate of 710°0; the rate was 49 9% in those with double defects (combinations to abnormal variables of count, motility, or morphology) and 38-9% (ejaculates in which count, motility, and morphology were all abnormal)." An overall clinical pregnancy rate of 13-3% per oocyte collection was recorded for the combined data (figure 2). Men whose spermatozoa do not achieve fertilisation or whose sperm concentrations are too low have benefited from further developments in assisted reproduction, which include the use of microdrop inseminations-eg, subzonal sperm microinjection (figure 3), in which a few spermatozoa are introduced between the zona pellucida and the oolemma, and intracytoplasmic injection of spermatozoa (ICSI) in which a single spermatozoa is injected directly into the cytoplasm of the oocyte.41 With ICSI, 64% of successfully injected oocytes were fertilised and there was a 35% clinical pregnancy rate per started cycle. In only 15 of 150 patients was embryo transfer not achieved, even though the men who entered that study had less than 5% normal fertilisation in standard IVF, or less than 500 000 progressively motile spermatozoa in the whole ejaculate, or had not achieved fertilisation after subzonal microinjection. Lately, ICSI has been successful in patients with 100% abnormal sperm morphology and severely compromised sperm motility with the use of spermatozoa retrieved from the epididymis. This technique promises to revolutionise the management of severe male factor infertility. In men with congenital absence of the vas deferens, spermatozoa recovered from the epididymis by surgical methods and subjected to motility enhancement with oxypentifylline or 2-deoxyadenosine can fertilise oocytes in vitro. Despite reported fertilisation rates ranging from 30 to 60%, the pregnancy rates have been disappointingly variables The recent use of ICSI has resulted in several clinical pregnancies and may offer higher pregnancy rates.41,42 However, care should be taken in evaluating the genetic status of these men (see above). years,
Figure 2: Cumulative pregnancy rates from couples undertaking IVF for male Infertility versus spontaneous pregnancy rates of same cohort (non-IVF programmes) From Yates C, PhD. Thesis, Monash University, 1989, with permission. Number in parentheses indicates number of cycles on which calculation based.
has serious side-effects, especially aseptic necrosis of the head of the femur which occurs in about 1 in 500 cases. Placebo-controlled trials show a significant increase in pregnancy with either continuous or intermittent (given for the first 10 days of the partner’s menstrual cycle) therapy,36 and semen may be cryopreserved for later use (artificial insemination) with assisted reproduction. With the latter procedures, 50% of patients with autoimmunity achieve fertilisation without treatment
glucocorticoid treatment. Men with gonadotropin deficiency respond successfully to treatment with human FSH and leutinising hormone or human chorionic gonadotropin, or by intermittent GnRH pulsatile therapy. Such regimens are usually lengthy because of the 70-day cycle of spermatogenesis. In general, the results indicate that at least 50% of such men father children during treatment, frequently with sperm counts that are much lower than normal.37 Some cases of retrograde ejaculation may be successfully treated with sympathomimetic drugs. Otherwise, assistedreproduction techniques with spermatozoa isolated from the urine after previous adjustment of the urinary pH and osmolarity should be offered to the couple. Recently, vibration and electroejaculation have been introduced for treatment of retrograde ejaculation or anejaculation, mostly in tetraplegic and paraplegic patients.3$
we
Untreatable infertility
Couples whether
with
they
untreatable infertility, irrespective of due to male or female factors, require
are
Subzonal microinjection
Non-specific therapy Because there are no specific aetiological factors in about 50% of infertile men, development of a logical plan of management is difficult. Numerous drugs, including androgens and gonadotropins, have been proposed as treatments designed to increase sperm count, but none has been shown to substantially improve sperm count or motility in double-blind trials with placebo-treated control groups.
Several studies have shown that IVF has enabled many subfertile men to become fathers.39 In a prospective study of 287 couples with a mean duration of infertility of 5-5
Figure 3: Subzonal injection
sperm
Injection and Intracytoplasmic
1477
considerable
counselling. Such couples should be given an
accurate assessment
of their clinical
status
and informed of
their
inability to have a child with their own gametes. The possibilities of a childless marriage, the availability of adoption, or the use of donor semen should be raised to enable couples to make an informed choice about their future. It is also important to recognise that some men with irreversible infertility may have Leydig-cell insufficiency and such men will require testosterone replacement therapy. The future It is easy to say "prevention is better than cure", but the difficulty with infertility is that the available knowledge on pathogenesis is very poor. At a glance it may appear as if most clinics are able to find a cause in about 85% of cases. However, analysis of published work must lead to the conclusion that diagnoses such as asthenospermia or oligozoospermia are purely descriptive. Sometimes even the term "male factor" is used as a diagnosis. The truth is, however, that these diagnoses in most cases cover up our ignorance. Infertility may be regarded as an indicator of more general systemic effects. Thus, the importance of the high rate of infertility that we are now witnessing may be even larger than the 15% subfecundity rate in the industrialised
world would indicate. Is
infertility becoming more frequent? Unfortunately, we cannot answer this question owing to lack of systematic records in the past. However, there is evidence that human semen quality has declined substantially during the past 50 years."" During the same period the incidence of testicular cancer, which is usually associated with poor semen quality, has increased in several countries.44 Thus, although our understanding of the biological processes behind infertility is still rather fundamental, we know enough to make us worry. Financial support number 92-016.
was
received from the Danish Cancer
Society, grant
References 1
2 3
4
5
6
7
8
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34
Temple-Smith PD, Southwick GJ, Yates CA, Trounson AO, de Kretser DM. Human pregnancy by IVF using sperm aspirated from the epididymis. J In Vitro Fert Embryo Transf 1985; 2: 119-22. Silber SJ, Ord T, Balmaceda J, Patrizio P, Asch RH. Congenital absence of the vas deferens: the fertilizing capapcity of human epididymal sperm. N Engl J Med 1990; 323: 1788-92. Baker HWG, Burger HG, de Kretser DM, Hudson B, Rennie GC, Straffon WGE. Failure of testicular vein ligation to increase fertility in men with varicocele. BMJ 1985; 291: 1678-80. World Health Organisation. The influence of varicocele on parameters of fertility in a large group of men presenting to infertility clinics.
Fertil Steril 1992; 57: 1289-93. 35 Kunnen M, Comhaire F. Nonsurgical care of varicocele by transcatheter embolization of the internal spermatic beins with a tissue adhesive (Histoacryl transparent). In: Casteneda-Zuniga WR, Tadavarthy SM, eds. International radiology. Baltimore: Williams & Wilkins 1992: 72-100. 36 Hendry WF, Hughes L, Scammell G, Pryor JP, Hargreave TB. Comparison of prednisolone and placebo in subfertile man with antibodies to spermatozoa. Lancet 1990; 335: 85-88. 37 Crowley WF, Whitcomb RW. Gonadotropin-releasing hormone deficiency in men: diagnosis and treatment with exogenous gonadotropin-releasing hormone. Am J Obstet Gynecol 1990; 163: 1752-58.
38 Mallidis C, Lim TC, Hill ST, et al. Collection of semen from men in acute phase of spinal cord injury. Lancet 1994; 343: 1072-73. 39 de Kretser DM, Yates C, Kovacs GT. The use of IVF in the management of male infertility. Clin Obstet Gynecol 1985; 12: 767-73. 40 Yates CA. The use of reproductive technologies for the treatment of male infertility (PhD thesis). Melbourne: Monash University, 1992. 41 van Steirteghem AC, Nagy Z, Joris H, et al. High fertilization and implantation rates after intracytoplasmic sperm injection. Hum Reprod
42 Silber S. Extreme variability of fertilization
capacity of epididymal sperm from different patients: the need for micromanipulation. In: Proceedings of VIIth World Congress on In Vitro Fertilization and Alternate Assisted Reproduction. Kyoto, Japan (in press). E, Giwercman A, Keiding N, Skakkebaek NE. Evidence for decreasing quality of semen during past 50 years. BMJ 1992; 305:
43 Carlsen
609-13. 44 Møller H. Clues
to the aetiology of testicular germ cell tumours from descriptive epidemiology. Eur Urol 1993; 23: 8-15.
1993; 8: 1061-66.
Hyp othesis Physiological importance of dehydroepiandrosterone
Summary
Introduction
Dehydroepiandrosterone (DHEA), with its sulphate conjugate (DHEAS), is the most abundant steroid hormone in the circulation but its physiological importance is unclear. We propose that DHEA has either oestrogen-like or androgen-like effects depending on the hormonal milieu. In premenopausal women DHEA is either an oestrogen antagonist, perhaps through the competitive binding of its metabolite 5androstene-3&bgr;,17&bgr;-diol (ADIOL) and oestradiol to the oestrogen receptor, or an androgen through its metabolism to
Dehydroepiandrosterone (DHEA) unconjugated or as its sulphate (DHEAS) is the major secretory steroidal product of the adrenal gland. The serum concentration of DHEAS is 300-500 times higher than that of DHEA and 20 times higher than of any other steroid hormone. While DHEAS is bound to albumin and forms a circulating reservoir, DHEA probably is more active at the tissue level. DHEA is considered as a weak androgen, and its concentration
androstenedione and testosterone. In women DHEA contributes to abdominal obesity and insulin resistance: in the premenopausal high oestrogen concentrations may counterbalance the androgenic effects of DHEA but in the postmenopausal metabolism to testosterone may increase the risk of cardiovascular disease, though this effect may be counterbalanced by the age-dependent decline in DHEA and also by the oestradiol-like effects of ADIOL. In some breast cancer cell lines in a low oestrogen milieu DHEA has an oestradiol-like effect, stimulating tumour growth, whereas in oestradiol abundance DHEA antagonises the growthstimulating effect of oestradiol. In men, with an androgenic milieu, DHEA acts like an oestrogen and protects against cardiovascular disease.
has a greater diurnal variation than DHEAS has. The secretion of DHEAS is stimulated by corticotropin (ACTH), but responsiveness of DHEAS to stimulation decreases with advancing age and the mean concentration of DHEAS in serum is reduced progressively from a peak at age 25 to less than 20% of that peak before the age of 70.1 Heredity has an impact on DHEAS concentrations too.2 Despite the abundance of DHEA and DHEAS their physiological role has remained unknown. In vitro and in vivo data suggest oestrogen or androgen like effects, depending on sex hormone homoeostasis.3 Also the DHEA metabolite 5-androstene-3(3, 17p-diol (ADIOL) has both androgen and oestrogenic effects in human myometrial tissue and in mammary cancer cells.4 In these cells ADIOL is 500 times more potent as an inhibitor of oestrogen binding than DHEA. The oestrogen-like effects of ADIOL, which is structurally closer to oestradiol than to oestrone or oestriol, are observed at physiological concentrations in breast cancer cells. S,6 In women 100% and in men about 60% of ADIOL is derived from DHEA.7 In postmenopausal women DHEA administration is strongly
androgenic, lowering sex hormone binding globulin (SHBG) and raising free testosterone.8 We propose that the enigma of the role of DHEA and DHEAS in abdominal obesity, insulin resistance, cardiovascular diseases or some forms of breast cancer can partly be explained by their dual actions as oestrogen or as androgen (table). Abdominal
obesity and Insulin resistance
healthy individuals the site-specific regulation of lipoprotein lipase (LPL) activity plays an important part in the maintenance of normal body fat distribution.9 Activation of the corticotropin-releasing factor (ACTH) cortisol (DHEA) axis increases the accumulation of visceral In
Second Department of Medicine, Helsinki University Hospital, FIN-00290 Helsinki, Finland (P Eberling MD, V A Koivisto MD)
Correspondence to: Dr Veikko A Koivisto
1479
iew
acticle
Pathogenesis and management of male infertility
Recent research has brought good news for infertile couples inasmuch as there are new treatment strategies, such as in-vitro fertilisation (IVF) and microinsemination. The bad news, however, is that this progress is restricted mainly to treatment of symptoms; there has been little gain in prevention and clarification of the underlying causes. Here we focus on male infertility, which has received little attention both scientifically and in medical practice. About 15% of all couples will experience primary or secondary infertility at some time during their reproductive lives.1,2 In about half these cases, there is a contributing male factor. However, the distinction between a man with normal fertility and one with reduced fertility may be difficult. According to the WHO classification, a human semen specimen is normal even if up to 70% of the spermatozoa have abnormal morphology (figure l)-a much higher percentage than in most other mammals. A high number of abnormal sperm heads is associated with decreased fertilisation capacity in animals and in human beings.3 Furthermore, the moderately high number of spermatozoa with abnormal heads in otherwise normal men in the industrialised world could reflect a general health
including prolactinoma, craniopharyngioma, other brain tumours, or radiation treatment. Although patients with gonadotropin insufficiency occasionally present via infertility clinics, the frequency of this disorder in infertility is small (ie, less than 0-5%).
problem. An important point is that male infertility is not an entity but reflects a variety of different pathogenetic mechanisms. shall review the causes from a functional viewpoint (panel), and our description will not be weighted according to prevalence. Rather, the focus will be on aspects of male infertility for which recent research has revealed new information. Thus
we
Causes of male
Infertility
Impaired sperm production and function Hypothalamic pituitary disorders A primary lesion in the pituitary gland or hypothalamus may secondarily lead to hypogonadism. The congenital form of hypogonadotropic hypogonadism (Kallmann’s syndrome) is due to a deficiency of gonadotropin-releasing hormone (GnRH). There is a large excess of men. Recently a deletion of a single gene, Kalig-2, has been found in the X-linked form of the disease.4 This gene encodes for certain neurons that migrate during fetal life, including those involved in the production of GnRH. The lack of gonadotropic hormones before and after birth seems to explain the frequently observed testicular maldescent as well as the absence of pubertal development. The acquired form of hypogonadotropic hypogonadism is most often due to pituitary adenomas University Department of Growth and Reproduction, Rigshospitalet, DK-2100 Copenhagen, Denmark (Prof N E Skakkebæk MD, A Giwercman MD); and Institute of Reproduction and Development, Monash University, Monash Medical Centre, Victoria, Australia (Prof D de Kretser MD) Correspondence to: Prof Niels
E Skakkebæk
Figure
1: Smears of semen
samples of (a) healthy man and (b)
bullI Note that high proportion of human spermatozoa is abnormally shaped with enlarged irregular heads. By contrast, bull spermatozoa are all normal with regular heads.
Genetic factors
including chromosome abnormalities The 47,XXY karyotype (Klinefelter’s syndrome) and its variants are almost always associated with azoospermia. Although the cause of testicular failure is clear, the pathogenesis is unknown. It is interesting that the extra X chromosome apparently causes little effect on the structure of the seminiferous tubule before puberty when an overwhelming destruction of the seminiferous epithelium takes place. Some patients with Klinefelter’s syndrome do, in fact, have significant growth of the testes early in puberty followed by a subsequent enormous shrinkage of the testes resulting in the well-known adult phenotype with microtestis. Men with an extra Y chromosome have various degrees of spermatogenic impairment, ranging from normal spermatogenesis to spermatogenic arrest and the Sertolicell-only pattern. Autosomal chromosome rearrangements including translocation may also result in reduced fertility, 1473
testicular biopsy samples of the contralateral testis in men with unilateral testicular cancer, severe impairment of spermatogenesis was present in 25% of the cases, including Sertoli-cell-only pattern, spermatogenic arrest, and carcinoma-in-situ.9 Semen quality at the time of diagnosis of the unilateral testicular cancer is also substantially impaired. Testicular cancer has its origin in carcinoma-insitu cells which even in adult men express fetal antigens and may be of fetal origin.10,11
Panel: Known causes of male Infertility Mechanism Absent testicular
Cause/pathogenesis Anorchia Bilateral castration
tissue
Impaired sperm production or
Hypogonadotropic hypogonadism ,
function
Klinefetter’s syndrome variants 47.XXY mates; 46,XX males Partial androgen insensitivity Autosomal rearrangements AZF-gene deletions
Germ-cell aplasia In many men with azoospermia, the seminiferous tubules contain only Sertoli cells. This cytological appearance can result from numerous causes, such as cryptorchidism, cytotoxic drugs, or irradiation (see below). However, in many cases the aetiology is unknown. The absence of germ cells may be due to factors present during fetal life. Furthermore, a subtle Leydig-cell insufficiency may be associated with Sertoli-cell-only
Spermatocytic arrest Cryptorchidism Cancer of testis Varicocele
Sertoli-celt-oniy Irradiation
Cytotoxic drugs Other drugs Environmental agents
.
.
Impaired sperm transport
Autoimmune infertility Epididymai blockage of vas deferens and other parts in seminal pathways
Ejaculatory failure Previous vasectomy
Impotence Kartagener’s syndrome Disturbances in sperm-oocyte fusion
Abnormal egg-binding proteins
Recurrent
Chromosomal aberrations
miscarriage is heterogeneous. For unknown reasons autosomal translocations may result in more severe impairment of fertility in the male than in the female. Chromosome abnormalities that give rise to unbalanced gametes may also be associated with repeated abortions. The arrest of spermatogenesis may, in rare cases, be due to impaired chromosome pairing in meiosis, resulting in azoospermia. A high proportion of parental consanguinity indicates that the disorder may be caused by a recessive mutation. Recently a genetic region controlling spermatogenesis in human beings-human azoospermia factor (AZF)-has been localised to the long arm of the Y chromosome,S and disturbed spermatogenesis and azoospermia have been recorded in men with deletions corresponding to the AZF region.6 However, the quantitative role of genetic abnormalities in men with unexplained spermatogenic disorders remains unclear.
although the pattern
Undescended testis The undescended testis is associated impaired spermatogenesis, although the extent of impairment may vary from a complete Sertoli-cell-only pattern to only a slight reduction in the number of germ cells.7 The fact that spermatogenesis is also impaired in the contralateral testis in patients with unilateral maldescent seems to indicate that some patients with maldescent have a congenital defect of the germ-cell population. Some investigators believe that the suprascrotal position of the testes in childhood causes the further decrease in the number of germ cells. Therefore, early treatment of cryptorchidism (before age 1 or 2) has been advocated. Data from the UK suggest that the rate of cryptorchidism is with
increasing.8 Testicular cancer Testicular cancer is associated with increased risk of impaired spermatogenesis. In a study 1474
an on
syndrome. Drugs It is striking that we know so little about the effects on fertility of commonly used drugs. In most countries the testing of drugs does include toxicity studies of the reproductive organs in animals. The safety checks in clinical trials generally do not include tests to elucidate the function and impairment of the human gonad. Impaired semen quality has been detected by chance during the use of drugs that were given routinely before their toxic effect was known. For example, sulphasalazine, which is used to treat inflammatory bowel diseases, can drastically reduce semen quality. Although the effects seem to be reversible when this drug is used in moderate doses for a limited time, the production of spermatozoa may be permanently impaired. Some antihypertensive drugs (eg, 0-blockers) may cause impotence. Anabolic steroids, which are widely used by athletes and body-builders, have severe side-effects on reproduction including oligozoospermia and azoospermia. The numerous cytotoxic drugs that are used to treat cancer and autoimmune disease are potentially damaging for gonadal function-especially the alkylating agents (eg, cyclophosphamide, procarbazine, cisplatin), which cause gonadal failure. However, there may be striking differences between the effects of the same drug on men and women. 12
Environmental factors Several environmental toxicants known to impair reproductive function have been identified in the workplace during the past 15 years. In addition to the chlorinated nematocide dibromochloropropane (DBCP) and chlordecone, there is strong evidence of spermatotoxic effects of other pesticides, such as carbaryl and ethylenedibromide, of some glycol ethers (with widespread use in paintings, printing inks, and adhesives), and of the metals lead, cadmium, and mercury. Male metal welders may be at increased risk of subfecundity, although the nature of the harmful exposures remains to be identified.13 From limited data it appears that the human seminiferous epithelium is more vulnerable to toxicants than is the testis of other animals. The reproductive system is especially vulnerable during development. Therefore, it is important to study possible environmental effects on reproduction in more than one generation. Work with laboratory animals has shown that irradiation of a pregnant female can cause total depletion of fetal germ cells without otherwise affecting the fetus or the mother. Thus, in the search for environmental factors affecting reproduction the focus should perhaps be more on the role of environmental agents on the fetus. Recently, the oestrogenic effect of several
environmental toxins has attracted attention as a possible cause of defects in the male reproductive organs.ll Nutrition and socioeconomic factors may also be important. The hypothalamic-GnRH pulse generator, which controls gonadal function, is affected by several hormonal, metabolic, and neural signals. Therefore, stress, undernutrition, socioeconomic problems, emotional deprivation, and drugs may all affect the onset and maintenance of reproductive function.14 Several life-style factors may have consequences for reproduction, including diet, clothing, exercise, and the use of alcohol, tobacco, and recreational drugs (eg, marijuana). Little is known about the effects of these factors on semen quality and therefore on male fertility potential. Varicocele This condition is present in 25-40% of men attending infertility clinics compared with about 10-15 % of men in the general population. The pathogenesis of spermatogenic failure in men with varicocele is largely unknown. One suggestion is that this failure is due to increased temperature, accumulation of CO2, and other noxious substances (including adrenal steroids and catecholamines) brought on by the venous reflux.ls However, the role of varicocele in infertility, especially with respect to its management, is controversial (see below).
Impaired sperm transport Autoimmune infertility The testis is an immunologically privileged site and spermatozoal antigens are effectively shielded from being recognised by the cells of the immune system. However, an autoimmune reaction against the spermatoza is seen in 5-10% of men being treated for infertility as an isolated abnormality. Circulating sperm antibodies are present in most men who have undergone vasectomy, and after reversal of the procedure these antibodies often appear in the seminal plasma. Unilateral or bilateral obstruction of the genital tract (either congenital or acquired), for reasons other than vasectomy, may also be associated with an autoimmune response against spermatozoa. In addition, epididymitis and varicocele may be associated with sperm antibodies. The most extensive studies on the importance of the immunoresponse for fertility have been done on men who have undergone vasectomy reversal. When there is a close association between the presence of antibodies and fertility potential, IgA in the semen appears to have a more important role than does IgG.16
Other
Sexually transmitted diseases may cause and lead to blockage of the ductal system, epididymitis in resulting permanent azoospermia. Obstructive azoospermia can also be due to agenesis of the epididymis and other parts of the ductal system including the vas deferens. Some of these cases seem to be of genetic origin. Congenital bilateral agenesis of the vas deferens is found in most patients with cystic fibrosis. Recently it has been shown that point mutations of the cystic fibrosis gene may causes
be present in at least two-thirds of men with isolated bilateral agenesis of the vas deferens without any other symptoms of cystic fibrosis." This finding has practical implications for the management (with assistedreproduction technology) of azoospermic men with preserved spermatogenesis and agenesis of the vas deferens, since genetic counselling may be indicated. Anejaculation or retrograde ejaculation may occur in diabetic patients as well as after retroperitoneal lymph-node dissection, spinal cord injury, and bladder-neck surgery. Other types of
sexual
dysfunction (including impotence) are, however, of infertility. Once the spermatozoa have been into the female tract, their motility depends on ejaculated their forward motion. Patients with the rare Kartagener’s syndrome (immotile cilia syndrome) are unable to produce motile spermatozoa owing to missing dynein arms. rare causes
Disturbances in sperm-oocyte fusion Studies in laboratory animals and man have shown that complementary adhesion molecules are located on the surface of oocytes and spermatozoa.18,19 These molecules interact and lead to fusion of the gametes (fertilisation). In the zona pellucida, two proteins called ZP2 and ZP3 seem to be especially involved in the adhesion of the spermatozoan to the oocyte. sp56 and (pro)acrosin are possible complementary egg-binding proteins on the spermatozoa. The function of this system seems important not only for fusion but also for prevention of polyspermy. Abnormalities in the adhesion molecules on the gamete surface may potentially contribute to infertility, although the clinical significance of these molecules have not been documented. Reactive oxygen species generated by leucocytes or the spermatozoa themselves may also have a role in sperm-oocyte fusion .20
Unexplained infertility In about 15%of couples who seek help no apparent cause can be found: semen quality fulfils the criteria for normalcy, and no defect in the woman’s reproductive system can be found. It is common to use the term unexplained infertility for such cases .20 However, different laboratories use different methods of investigation, and a man with unexplained infertility may obtain a diagnosis if he is seen at another clinic. Furthermore, a classification of a semen sample as normal does not necessarily mean that the specimen has the capacity to fertilise. Neither conventional semen analysis nor modern sperm function tests can reveal the exact fertilising capacity of a particular semen sample; they may indicate fertility potential and nothing more. Introduction of new methods of assessment of sperm function (eg, measurement of reactive oxygen species2O) may move more and more cases of unexplained infertility into categories of well-defined causes. Couples with unexplained infertility often shown fertilisation failure during IVF despite apparently normal gametes.
Management of the Infertile male Introduction of new assisted-reproduction techniques has moved the interest of many infertility clinics from the man as a whole to his semen and its usefulness for assisted fertilisation. Nonetheless, it is essential that the male partner is thoroughly investigated to clarify whether any of the potentially curable causes of infertility is present. It is important to emphasise that careful clinical examination may give important information, which in some cases-eg, Klinefelter’s syndrome, Kallmann’s syndrome, varicocele, or cryptorchidism-may be sufficient to establish the cause of infertility with a high degree of certainty.
Investigations Semen analysis
In view of the substantial variability of men, at least 2-3 analyses, including evaluation of volume, sperm concentration, motility, and morphology, should be done.21 The presence of sperm sperm counts
in
some
1475
antibodies,
can
easily be detected by the immunobead
or
mixed antiglobulin reaction tests which localise IgG or IgA to specific regions of spermatozoa. Functional impairment caused by antibodies is evaluated by the sperm mucuspenetration test, which assesses the capacity of spermatozoa to move through a column of mid-cycle cervical mucus. Up to 1 million leucocytes per mL of semen is regarded as normal (peroxidase staining technique). However, the use of monoclonal antibodies to specific leucocytes questions the validity of these data.22 The relation between leucocyte count and the presence of genital tract inflammation still requires confirmation. Accessory gland function can be assessed by measurement of seminal fructose (seminal vesicles) and acid phosphatase, zinc, or citrate (prostate). Their concentrations can be low in the presence of prostatitis or vesiculitis, but a normal value does not exclude the presence of infection. An acid pH and low fructose concentrations can indicate absence of seminal vesicles and the vas deferens. Post-ejaculatory urine should be investigated for presence of spermatozoa if retrograde ejaculation is suspected.
New tests of sperm function The poor prediction of fertilising capacity by routine semen analysis has led to new tests of sperm function; of these, the strict morphology evaluations, acrosomal assessment, and sperm-zona binding have provided the best assessments.23,24 The tests of human sperm/zona-pellucida interactions are done with oocytes that can be used fresh or after storage in concentrated salt solutions. Since these zonae and oocytes represent a heterogeneous population, it is important that control and test spermatozoa are used. In-vitro studies suggest that sperm-zona binding ratios and the proportion of zonae penetrated by spermatozoa give a powerful prediction of fertilisation in IVF.24 The production of reactive oxygen species by sperm from infertile men is significantly raised and correlates with their capacity for fertilisation.2s It has been proposed that these reactive oxygen species cause lipid peroxidation in sperm membranes and thereby interfere with their ability to react in the membrane fusion events that are associated with fertilisation. Measurement of reactive oxygen species production is easy, but further studies on larger populations of patients are needed to see whether the encouraging results on fertilising ability are confirmed. Endocrine evaluation
Although gonadotropin deficiency is uncommon, diagnosis of hypogonadotropic hypogonadism is important since treatment is available. The measurement of serum follicle-stimulating hormone (FSH) is generally regarded as valuable to distinguish patients with azoospermia who have obstruction (normal FSH) from those who have seminiferous tubule destruction (raised FSH). However, recent data indicate that in azoospermic men an
obstruction
cannot
be excluded
even
if FSH is
substantially raised provided that at least one of the testes is of normal size. In 30% of men with severe oligozoospermia or azoospermia resulting from severe damage to the seminiferous epithelium, leutinising hormone concentrations are high and testosterone concentrations are low.26
Chromosomal and genetic studies These are most valuable in patients with azoospermia, high FSH, and small testes (2-6 mL), with the diagnosis of Klinefelter’s syndrome (47,XXY) being made in up to 20% of some series. Screening for the cystic fibrosis gene is required in patients with congenital absence of the vas deferens.27 1476
biopsy Testicular biopsy can confirm the diagnosis of obstructive azoospermia (normal testis size associated with azoospermia). At varicocele surgery, a biopsy can be done to assess the state of the seminiferous epithelium and provide prognostic information to the patient. An additional benefit for the infertile man is the possibility of disclosing carcinoma-in-situ. The risk of early testicular malignant disease (carcinoma-in-situ) may be increased in infertile men, especially those with a history of cryptorchidism.28 Testicular ultrasonography This procedure can locate impalpable testes or those accompanied by a hydrocele and Testicular
also facilitate the detection of cysts or other abnormalities in the scrotum. Rectal ultrasound examination can also be used to assess prostate and seminal vesicle size and to diagnose ejaculatory duct obstruction. The latter is being recognised more commonly as a cause of obstructive azoospermia or severe oligozoospermia, and surgical intervention can improve fertility.29
Therapeutic approach In general, specific causes of male infertility should be sought and treated but when no cause is found, use of assisted-reproduction technology is the only option for the management of men with subfertile semen. Patients with obstructive azoospermia should be offered epididymovasostomy with microsurgical techniques, but the success of this procedure is dependent on the site of the obstruction. Low epididymal lesions are more successfully treated than high lesions since the size of the epididymal duct increases in the caudal region and in low lesions there is a greater length of epididymal duct for the process of epididymal sperm maturation. 30 In western societies, vasectomy reversal is frequently requested. The presence of sperm antibodies may complicate obstructive lesions and may be the reason for failure to achieve a pregnancy after technically successful reversal. In cases of failed reversal, in patients who decide not to proceed with surgery, or in patients with congenital absence of the vas deferens, surgical aspiration of spermatozoa from the epididymis for use in assisted reproduction is feasible.31,32 For obstruction at the level of the ejaculatory duct, recent data report encouraging results after panendoscopy and excision of the region of the prostatic urethra into which the ejaculatory ducts drain.29 The management of patients with a varicocele is contentious.33 Despite increasing evidence that varicocele does influence sperm production,34 there have been no properly controlled trials of varicocele ligation. In general, a long duration of infertility (2 years), a low sperm count, and a normal FSH would be reasons to undertake varicocele ligation. Raised FSH in association with severe oligozoospermia usually indicates testicular damage that is unlikely to recover from varicocele ligation. More recently, the successful radiological occlusion of spermatic veins by the installation of acrylamide glues or coils has been reported.35 Such an approach, however, requires excellent radiological intervention techniques. If genital tract infection is diagnosed, treatment with broad-spectrum antibiotics, such as trimethoprim,
erythromycin, and doxycycline, which gain access to the accessory glands should be given. Advice about the frequency of ejaculation to facilitate drainage of the accessory glands is also of value. Patients with anti-sperm antibodies as the cause of infertility may be offered prednisolone therapy, continuously or intermittently. This
showed that men with single defects (an abnormal count, motility, or morphology) achieved a fertilisation rate of 710°0; the rate was 49 9% in those with double defects (combinations to abnormal variables of count, motility, or morphology) and 38-9% (ejaculates in which count, motility, and morphology were all abnormal)." An overall clinical pregnancy rate of 13-3% per oocyte collection was recorded for the combined data (figure 2). Men whose spermatozoa do not achieve fertilisation or whose sperm concentrations are too low have benefited from further developments in assisted reproduction, which include the use of microdrop inseminations-eg, subzonal sperm microinjection (figure 3), in which a few spermatozoa are introduced between the zona pellucida and the oolemma, and intracytoplasmic injection of spermatozoa (ICSI) in which a single spermatozoa is injected directly into the cytoplasm of the oocyte.41 With ICSI, 64% of successfully injected oocytes were fertilised and there was a 35% clinical pregnancy rate per started cycle. In only 15 of 150 patients was embryo transfer not achieved, even though the men who entered that study had less than 5% normal fertilisation in standard IVF, or less than 500 000 progressively motile spermatozoa in the whole ejaculate, or had not achieved fertilisation after subzonal microinjection. Lately, ICSI has been successful in patients with 100% abnormal sperm morphology and severely compromised sperm motility with the use of spermatozoa retrieved from the epididymis. This technique promises to revolutionise the management of severe male factor infertility. In men with congenital absence of the vas deferens, spermatozoa recovered from the epididymis by surgical methods and subjected to motility enhancement with oxypentifylline or 2-deoxyadenosine can fertilise oocytes in vitro. Despite reported fertilisation rates ranging from 30 to 60%, the pregnancy rates have been disappointingly variables The recent use of ICSI has resulted in several clinical pregnancies and may offer higher pregnancy rates.41,42 However, care should be taken in evaluating the genetic status of these men (see above). years,
Figure 2: Cumulative pregnancy rates from couples undertaking IVF for male Infertility versus spontaneous pregnancy rates of same cohort (non-IVF programmes) From Yates C, PhD. Thesis, Monash University, 1989, with permission. Number in parentheses indicates number of cycles on which calculation based.
has serious side-effects, especially aseptic necrosis of the head of the femur which occurs in about 1 in 500 cases. Placebo-controlled trials show a significant increase in pregnancy with either continuous or intermittent (given for the first 10 days of the partner’s menstrual cycle) therapy,36 and semen may be cryopreserved for later use (artificial insemination) with assisted reproduction. With the latter procedures, 50% of patients with autoimmunity achieve fertilisation without treatment
glucocorticoid treatment. Men with gonadotropin deficiency respond successfully to treatment with human FSH and leutinising hormone or human chorionic gonadotropin, or by intermittent GnRH pulsatile therapy. Such regimens are usually lengthy because of the 70-day cycle of spermatogenesis. In general, the results indicate that at least 50% of such men father children during treatment, frequently with sperm counts that are much lower than normal.37 Some cases of retrograde ejaculation may be successfully treated with sympathomimetic drugs. Otherwise, assistedreproduction techniques with spermatozoa isolated from the urine after previous adjustment of the urinary pH and osmolarity should be offered to the couple. Recently, vibration and electroejaculation have been introduced for treatment of retrograde ejaculation or anejaculation, mostly in tetraplegic and paraplegic patients.3$
we
Untreatable infertility
Couples whether
with
they
untreatable infertility, irrespective of due to male or female factors, require
are
Subzonal microinjection
Non-specific therapy Because there are no specific aetiological factors in about 50% of infertile men, development of a logical plan of management is difficult. Numerous drugs, including androgens and gonadotropins, have been proposed as treatments designed to increase sperm count, but none has been shown to substantially improve sperm count or motility in double-blind trials with placebo-treated control groups.
Several studies have shown that IVF has enabled many subfertile men to become fathers.39 In a prospective study of 287 couples with a mean duration of infertility of 5-5
Figure 3: Subzonal injection
sperm
Injection and Intracytoplasmic
1477
considerable
counselling. Such couples should be given an
accurate assessment
of their clinical
status
and informed of
their
inability to have a child with their own gametes. The possibilities of a childless marriage, the availability of adoption, or the use of donor semen should be raised to enable couples to make an informed choice about their future. It is also important to recognise that some men with irreversible infertility may have Leydig-cell insufficiency and such men will require testosterone replacement therapy. The future It is easy to say "prevention is better than cure", but the difficulty with infertility is that the available knowledge on pathogenesis is very poor. At a glance it may appear as if most clinics are able to find a cause in about 85% of cases. However, analysis of published work must lead to the conclusion that diagnoses such as asthenospermia or oligozoospermia are purely descriptive. Sometimes even the term "male factor" is used as a diagnosis. The truth is, however, that these diagnoses in most cases cover up our ignorance. Infertility may be regarded as an indicator of more general systemic effects. Thus, the importance of the high rate of infertility that we are now witnessing may be even larger than the 15% subfecundity rate in the industrialised
world would indicate. Is
infertility becoming more frequent? Unfortunately, we cannot answer this question owing to lack of systematic records in the past. However, there is evidence that human semen quality has declined substantially during the past 50 years."" During the same period the incidence of testicular cancer, which is usually associated with poor semen quality, has increased in several countries.44 Thus, although our understanding of the biological processes behind infertility is still rather fundamental, we know enough to make us worry. Financial support number 92-016.
was
received from the Danish Cancer
Society, grant
References 1
2 3
4
5
6
7
8
Mosher WD, Pratt WF. Fecundity and infertility in the United States, 1965-1988. Advanced Data from Vital and Health Statistics. Hyattsville: National Center for Health Statistics, 1990. Templeton A, Fraser C, Thompson B. The epidemiology of infertility in Aberdeen. BMJ 1990; 301: 148-52. Kruger TF, Menkveld R, Stander FSH, et al. Sperm morphologic features as a prognostic factor in in vitro fertilization. Fertil Steril 1986; 46: 1118-23. Bick D, Sherins RJ, Pike L, et al. Brief report: intragenic deletion of the Kalig-1 gene in Kallmann’s syndrome. N Engl J Med 1992; 326: 1752-55. Simpson E, Chandler P, Goulmy E, Ma K, Hargreave TB, Chandley AC. Loss of the ’azoospermia factor’ (AZF) on Yq in man is not associated with loss of HYA. Hum Mol Genet 1993; 2: 469-71. Kun M, Inglis JD, Sharkey A, et al. A Y chromosome gene family with RNA-binding protein homology: candidates for the azoospermia factor AZF controlling human spermatogenesis. Cell 1993; 75: 1287-95. Giwercman A, Bruun E, Frimodt-Møller C, Skakkebaek NE. Prevalance of carcinoma in situ and other histopathological abnormalities in testes of men with a history of cryptorchidism. J Urol 1989; 142: 998-1002. John Radcliffe Hospital Cryptorchidism Study Group. Cryptorchidism: an apparent substantial increase since 1960. BMJ
1986; 293: 1401-04. Berthelsen JG, Skakkebaek NE. Gonadal function in men with testis cancer. Fertil Steril 1983; 39: 68-75. 10 Skakkebaek NE, Berthelsen JG, Giwercman A, Muller J. Carcinomain-situ of the testis: possible origin from gonocytes and precursor of all types of germ cell tumours except spermatocytoma. Int J Androl 1987;
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1392-95. 12 Damewood MD, Grochow LB. Prospects for fertility after chemotherapy or radiation for neoplastic disease. Fertil Steril 1986; 45: 443-59. 13 Bonde JPE. The risk of male subfecundity attributable to welding of metals: studies of semen quality, infertility, fertility, adverse pregnancy outcome and childhood malignancy. Int J Androl 1993; 16: 1-29. 14 Vermeulen A. Environment, human reproduction, menopause, and andropause. Envir Health Perspect 1993;; 101 (suppl 2): 91-100. 15 Comhaire F. The pathogenesis of epididymo-testicular dysfunction in varicocele: factors other than temperature. In: Zorgniotti AW, ed. Advances in experimental medicine and biology. Vol 286. Temperature and environmental effects on the testis. New York: Plenum Press, 1991: 281-88. 16 Meinertz H, Linnet L, Fogh-Andersen P, Hjort T. Antisperm antibodies and fertility after vasovasostomy: a follow-up study of 216 men. Fertil Steril 1990; 54: : 315-21. 17 Editorial. Congenital bilateral absence of the vas deferens and cystic fibrosis. Lancet 1992; 339: 1328-29. 18 van-Duin M, Polman JE, Verkoelen CC, et al. Cloning and characterization of the human sperm receptor ligand ZP3: evidence for a second polymorphic allele with a different frequency in the Caucasian and Japanese populations. Genomics 1992; 14: 1064-70. 19 Wassarman PM. Mouse gamete adhesion molecules. Biol Reprod 1992; 46:: 186-91. 20 Aitken RJ, Buckingham D, West K, Wu FC, Zikopoulos K, Richardson DW. Differential contribution of leucocytes and spermatozoa to the generation of reactive oxygen species in the ejaculates of oligozoospermic patients and fertile donors. J Reprod Fertil 1992; ; 94: 451-62. 21 World Health Organization. WHO laboratory manual for the examination of human semen and sperm-cervical mucus interaction. Cambridge: Cambridge University Press, 1992. 22 Barrat CLR, Kessopoulou E, Thompson LA, Tomlinson MJ, Cooke ID. The functional significance of leucocytes in human reproduction. Reprod Med Review (in press). 23 Kruger TF, Acosta AA, Simmons KF, Swanson RJ, Matta JF, Oehninger S. Predictive value of abnormal sperm morphology in in vitro fertilization. Fertil Steril 1988; 49: 112-17. 24 Liu DY, Baker HWG. Tests of human sperm function and fertilization in vitro. Fertil Steril 1992; 58: 465-83. 25 Aitken RJ, Clarkson JS. Cellular basis of defective sperm function and its association with the genesis of reactive oxygen species by human spermatozoa. J Reprod Fertil 1987; 81: 459-69. 26 de Kretser DM, Burger HG, Fortune D, et al. Hormonal, histological and genetic studies on male infertility. J Clin Metab 1972; 35: 392-401. 27
Angulano A, Oates RD, Amos JA, et al. Congenital bilateral absence of the vas deferens: a primary genital form of cystic fibrosis. JAMA 1992;
267: 1794-97. 28 Giwercman A, von der Maase H, Skakkebaek NE. Epidemiological and clinical aspects of carcinoma in situ of the testis. Eur Urol 1993; 23: 104-14. 29 Meacham RB, Hellersten ZDK, Lipschultz LI. Evaluation and treatment of ejaculatory duct obstruction in the infertile male. Fertil Steril 1993; 59: 393-97. 30 Southwick GF, Temple-Smith PD. Epididymal microsurgery: current techniques and new horizons. Microsurgery 1988; 9: 266-77. 31
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Fertil Steril 1992; 57: 1289-93. 35 Kunnen M, Comhaire F. Nonsurgical care of varicocele by transcatheter embolization of the internal spermatic beins with a tissue adhesive (Histoacryl transparent). In: Casteneda-Zuniga WR, Tadavarthy SM, eds. International radiology. Baltimore: Williams & Wilkins 1992: 72-100. 36 Hendry WF, Hughes L, Scammell G, Pryor JP, Hargreave TB. Comparison of prednisolone and placebo in subfertile man with antibodies to spermatozoa. Lancet 1990; 335: 85-88. 37 Crowley WF, Whitcomb RW. Gonadotropin-releasing hormone deficiency in men: diagnosis and treatment with exogenous gonadotropin-releasing hormone. Am J Obstet Gynecol 1990; 163: 1752-58.
38 Mallidis C, Lim TC, Hill ST, et al. Collection of semen from men in acute phase of spinal cord injury. Lancet 1994; 343: 1072-73. 39 de Kretser DM, Yates C, Kovacs GT. The use of IVF in the management of male infertility. Clin Obstet Gynecol 1985; 12: 767-73. 40 Yates CA. The use of reproductive technologies for the treatment of male infertility (PhD thesis). Melbourne: Monash University, 1992. 41 van Steirteghem AC, Nagy Z, Joris H, et al. High fertilization and implantation rates after intracytoplasmic sperm injection. Hum Reprod
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capacity of epididymal sperm from different patients: the need for micromanipulation. In: Proceedings of VIIth World Congress on In Vitro Fertilization and Alternate Assisted Reproduction. Kyoto, Japan (in press). E, Giwercman A, Keiding N, Skakkebaek NE. Evidence for decreasing quality of semen during past 50 years. BMJ 1992; 305:
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Hyp othesis Physiological importance of dehydroepiandrosterone
Summary
Introduction
Dehydroepiandrosterone (DHEA), with its sulphate conjugate (DHEAS), is the most abundant steroid hormone in the circulation but its physiological importance is unclear. We propose that DHEA has either oestrogen-like or androgen-like effects depending on the hormonal milieu. In premenopausal women DHEA is either an oestrogen antagonist, perhaps through the competitive binding of its metabolite 5androstene-3&bgr;,17&bgr;-diol (ADIOL) and oestradiol to the oestrogen receptor, or an androgen through its metabolism to
Dehydroepiandrosterone (DHEA) unconjugated or as its sulphate (DHEAS) is the major secretory steroidal product of the adrenal gland. The serum concentration of DHEAS is 300-500 times higher than that of DHEA and 20 times higher than of any other steroid hormone. While DHEAS is bound to albumin and forms a circulating reservoir, DHEA probably is more active at the tissue level. DHEA is considered as a weak androgen, and its concentration
androstenedione and testosterone. In women DHEA contributes to abdominal obesity and insulin resistance: in the premenopausal high oestrogen concentrations may counterbalance the androgenic effects of DHEA but in the postmenopausal metabolism to testosterone may increase the risk of cardiovascular disease, though this effect may be counterbalanced by the age-dependent decline in DHEA and also by the oestradiol-like effects of ADIOL. In some breast cancer cell lines in a low oestrogen milieu DHEA has an oestradiol-like effect, stimulating tumour growth, whereas in oestradiol abundance DHEA antagonises the growthstimulating effect of oestradiol. In men, with an androgenic milieu, DHEA acts like an oestrogen and protects against cardiovascular disease.
has a greater diurnal variation than DHEAS has. The secretion of DHEAS is stimulated by corticotropin (ACTH), but responsiveness of DHEAS to stimulation decreases with advancing age and the mean concentration of DHEAS in serum is reduced progressively from a peak at age 25 to less than 20% of that peak before the age of 70.1 Heredity has an impact on DHEAS concentrations too.2 Despite the abundance of DHEA and DHEAS their physiological role has remained unknown. In vitro and in vivo data suggest oestrogen or androgen like effects, depending on sex hormone homoeostasis.3 Also the DHEA metabolite 5-androstene-3(3, 17p-diol (ADIOL) has both androgen and oestrogenic effects in human myometrial tissue and in mammary cancer cells.4 In these cells ADIOL is 500 times more potent as an inhibitor of oestrogen binding than DHEA. The oestrogen-like effects of ADIOL, which is structurally closer to oestradiol than to oestrone or oestriol, are observed at physiological concentrations in breast cancer cells. S,6 In women 100% and in men about 60% of ADIOL is derived from DHEA.7 In postmenopausal women DHEA administration is strongly
androgenic, lowering sex hormone binding globulin (SHBG) and raising free testosterone.8 We propose that the enigma of the role of DHEA and DHEAS in abdominal obesity, insulin resistance, cardiovascular diseases or some forms of breast cancer can partly be explained by their dual actions as oestrogen or as androgen (table). Abdominal
obesity and Insulin resistance
healthy individuals the site-specific regulation of lipoprotein lipase (LPL) activity plays an important part in the maintenance of normal body fat distribution.9 Activation of the corticotropin-releasing factor (ACTH) cortisol (DHEA) axis increases the accumulation of visceral In
Second Department of Medicine, Helsinki University Hospital, FIN-00290 Helsinki, Finland (P Eberling MD, V A Koivisto MD)
Correspondence to: Dr Veikko A Koivisto
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