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SERUM INHIBIN B LEVELS AND THE RESPONSE TO GONADOTROPIN STIMULATION TEST IN PUBERTAL BOYS WITH VARICOCELE
0022-5347/99/1623-0875/0
Vol. 162,875-877, September 1999 Printed in U.S.A.
THEJOIJRNAL OF UROLOGY Copyright 0 1999 by AMERICAN UROLOCICAL ASSOCIATION, INC.
SERUM INHIBIN B LEVELS AND THE RESPONSE TO GONADOTROPIN STIMULATION TEST IN PUBERTAL BOYS WITH VARICOCELE ADRIANA CARRILLO, ABBEY GERSHBEIN, KENNETH I. GLASSBERG, AND MARC0 DANON From the Division of Pediatric Urology, State University of New York Downstate Medical Center in Brooklyn and Division of Pediatric Endocrinology, Maimonides Medical Center, Brooklyn, New York and Miami Children's Hospital, Miami, Florida
ABSTRACT
Purpose: The impact of varicoceles on gonadal function in adolescents has been evaluated using several parameters, including size of testes, hormonal levels and provocative endocrine testing. Inhibin B has been demonstrated to be decreased in men with testicular damage from conditions other than varicocele. We determine whether inhibin B levels are low in adolescent boys with varicocele, and if there is a relationship between inhibin B and an exaggerated response to gonadotropin-releasing hormone (Gn-RH) stimulation testing, testicular hypertrophy andor varicocele bilaterality. Materials and Methods: We studied 9 boys at Tanner stages I11 to V of pubertal development who had either left or bilateral varicoceles. Basal inhibin B, follicle-stimulating hormone, luteinizing hormone and testosterone were measured. Each patient underwent Gn-RH stimulation testing. Results: All patients had essentially normal inhibin B levels for Tanner stage. Of the 9 boys 4 had an exaggerated response to Gn-RH stimulating testing. Inhibin B levels did not vary significantly either with the presence of bilateral or unilateral varicoceles or asymmetric testis. Conclusions: The lack of correlation between inhibin B levels and the aforementioned parameters failed to suggest that inhibin B has a significant role in the clinical assessment of testicular function in adolescents with varicocele. Further studies of larger populations may further elucidate the value of inhibin B levels and varicoceles. KEYWORDS:varicocele, gonadotropins, inhibin, puberty
Varicocele is considered the most common identifiable cause of infertility in men and may be present in as many as 15% of boys by age 15 years.' In some cases varicocele can induce changes in testicular growth and histology that may ultimately affect spermatogenesis.2-4 The impact of varicoceles on gonadal function in adolescents has been evaluated using several parameters, including testicular size, hormonal levels and provocative endocrine testing. In adolescents with testicular growth arrest a n exaggerated gonadotropin response to gonadotropin stimulation may be indicative of gonadal damage.5.6 Another potential marker of testicular damage is serum inhibin that is secreted by the Sertoli cells.7.8 Inhibin B has a critical role in folliclestimulating hormone (FSH) regulation via a closed loop negative feedback system.9 Recently, a new highly sensitive assay was developed to differentiate between the biologically inactive inhibin A and the biologically active inhibin B in vitro.10-12 In 1996 Illingworth et a1 demonstrated barely detectable inhibin B levels in men with azoospermia, suggesting that low inhibin B levels correlate with damage asAccepted for publication April 16, 1999.
sociated with infertility.10 Reduced basal serum inhibin levels as well as an exaggerated gonadotropin response to gonadotropin-releasing hormone (Gn-RH) may help to identify which patients would benefit from surgery. We determine whether inhibin B levels are indicative of early testicular damage in adolescents with varicoceles, and whether inhibin levels correlate with response t o Gn-RH stimulation testing, testicular volume loss a n d o r bilaterality. Identifymg an objective means to assess for testicular damage in adolescents with varicoceles may be useful in the decision making process of varicocelectomy. METHODS
Our study included 9 adolescents 12 to 20 years old with either left or bilateral varicoceles diagnosed on routine physical examination. Pubertal development was staged according to Tanner criteria, and all patients were at Tanner stages I11 to V.1" Testicular volume was assessed using a Takihara ring orchidometer (table 1).Testicular asymmetry was considered present when the left testis was at least 3 cc smaller
TABLE1. Tanner stage, testicular volume, levels Pt.No. 1 2 3 4 5 6 7 8 9
Tanner Stage 5 5 5 4 3 5 4 4 3
Rt. Testicle (ml.) 12 20 12 12 15 15 10 10 12
Lt. testicle (ml.) 12 12 12 10 7 15 10 12 14
875
of Inhibin B and testosterone
Varicocele Side Bilat. Lt. Bilat. Bilat. Lt. Lt. Lt . Lt . Bilat.
Inhibin B (pgJml.1 120 102.5 314 349 438 196 177.9 150 156
Testosterone (ng./ml.) 21 112 435 329 372 329 337 68 479
876
EVALUATION OF PUBERTAL BOYS WITH VARICOCELE
than the right testis and its volume was less than 85% of the right side. The Gn-RH stimulation test was performed in a standardized fashion. Blood samples were obtained just before intravenous bolus injection of 100 pg. synthetic Gn-RH, and similar samples were drawn at 30,60,90 and 120 minutes after injection. The normal gonadotropin response to Gn-RH stimulation was calculated by subtracting the baseline (0 minute) value for FSH and luteinizing hormone (LH) from stimulation values (30 and 60 minutes). The maximal normal FSH value 30 and 60 minutes after stimulation was 8.2 mIU. Similarly, the maximal LH response values were 51.7 and 44.1 mIU a t 30 and 60 minutes, re~pectively.~ Serum FSH, LH and testosterone were analyzed by previously described radioimmunoassay techniques.14.l5 The low end LH sensitivity, interassay and intra-assay coefficients of variations were less than 3 mIU/ml., 9.7%and 6.4%,respectively. The low end FSH sensitivity, interassay and intraassay coefficients of variation were 0.3 mIU/ml., 4.7% and less than 3%,respectively. For serum testosterone the lower limit of detection, interassay and intra-assay coefficients of variation were 0.03 ng./ml., 9.9%and 5.9%,respectively. Inhibin B was measured with a double antibody enzyme immunometric assay using ultrasensitive inhibin B kits.16 Patient samples and standards were treated before the enzyme-linked immunosorbent assay (ELISA) with detergent, heated to lOOC and exposed to hydrogen peroxide. These treatments enhanced the specificity and sensitivity of ELISA. Coefficient of variation was less than 5% within plates and less than 7% between plates for both assays. Inhibin B had approximately 1%cross reaction with inhibin A. The detection limit was less than 15 pg./ml. for inhibin B assay. For statistical analysis data are presented as mean plus or minus standard error of mean. The absolute peak value and delta value were used to evaluate the gonadotropin response to Gn-RH test. The delta value was calculated by subtracting the baseline value of FSH and LH from their respective post-stimulation values. The relationships between inhibin B and other hormones were analyzed by forward stepwise multiple linear regression with p < 0.05 considered significant. RESULTS
The individual Tanner Stage, testicular volume, varicocele side, serum inhibin B as well as testosterone are shown in table 1. Mean serum inhibin B level was 231 ? 40 pg./ml. There was no statistically significant relationship when inhibin B levels were correlated with testes size, presence of bilateral varicoceles or response to Gn-RH stimulation testing. Of the 9 patients 4 had abnormal responses to Gn-RH stimulation tests suggestive of testicular dysfunction (table 2). Patients 2 and 6 had an elevated baseline FSH with normal baseline LH but a hyperreactive response for FSH and LH. Patient 5 had normal baseline FSH and LH with an
exaggerated LH response. Patient 7 had normal baseline gonadotropin levels with exaggerated FSH response to Gn-RH stimulation. Mean delta and peak LH values were 42 2 12 and 45 2 11 mIU/ml., respectively. There was no statistically significant correlation among delta LH, testosterone and inhibin B. There was a negative correlation between the peak and delta FSH with basal serum inhibin B (r = -0.47 and r = -0.44). Testosterone levels were not correlated with testicular volume, LH, FSH or inhibin B. Patients 1 and 8 had testosterone levels below what is expected for pubertal stage, suggesting gonadal dysfunction. DISCUSSION
Inhibin is a dimeric glycoprotein secreted by the Sertoli cells738 believed to regulate FSH secretion by a closed loop negative feedback mechanism.9 It was first postulated to exist in the 1920s by McCullagh who named it “the water soluble principle in the testis.”17 Initially, except for hypogonadotropic conditions,l8 there was no evidence to support a variation in inhibin levels when comparing fertile and infertile men which lead some to question the role of inhibin measurements in the clinical setting. Unfortunately, most early studies regarding inhibin are based upon heterologous assays which are not able to distinguish between the a and p forms due to cross-reactivity between the 2 dimers. Using the newer ELISA, Illingworth et a1 in 1996 demonstrated an inverse relationship between inhibin B and FSH concentrations,lO supporting the original hypothesis of McCullagh and demonstrating the critical role that inhibin B has in the regulation of gonadotropin secretion. It seems possible that inhibin B might be a useful marker of Sertoli and/or germ cell function in adolescents with varicoceles. Several authors have sought parameters that may be useful in predicting which adolescents are likely to benefit from varicocele ligation.19-21 Factors such as testicular volume loss, bilateral varicoceles and large varicoceles have served as indications for varicocele ligation in adolescents in whom seminal parameters are usually not available. None of our patients with ipsilateral testicular volume loss demonstrated decreased inhibin B levels. Perhaps the degree of damage to the testes in adolescents with varicoceles and testicular volume loss was not severe enough to affect serum inhibin B values. The Gn-RH stimulation test has been useful in evaluating patients with suspected testicular damage.22 Hudson et a1 studied infertile men with varicoceles and exaggerated gonadotropin responses to Gn-RH stimulation.23 Following varicocele ligation this response as well as spermatogenesis returned to normal. Kass et al reported an abnormal response to Gn-RH stimulation in almost a third of adolescents with varicoceles, an exaggerated LH response suggestive of Leydig cell dysfunction and an exaggerated FSH response suggestive of a defect at the level of the seminiferous tubules5 Similarly to their findings, we also found exaggerated LH response to Gn-RH stimulation in 3 of 9 patients, and abnor-
TABLE2 . FSH and LH responses to Gn-RH test -
FSH (mIU/rnl.)
~~
Pt. No. 1 2 3 4 5 6 7 8 9
LH (mIU/ml.)
0 Min.
30 Mins.
60 Mins.
90 Mins.
120 Mins.
0 Min.
30 Mins.
60 Mins.
90 Mins.
120 Mins.
11.7 25.6 6 2.6 3.7 18.7 3.3 1.5 4.9
19.7 42.7 9.1 3.1 9 33.6 20.6 4.1 8.2
18.5 37.8 9 3.3 9 34.2 18.5 4.2 9.8
17.3 36.3 9.1 3.5 8.5 32.6 12.6 4.2 9.5
18 38.8 8 3.3 8.4 30.3 11.2 3.5 9.2
8.7 5.8 3.5 <3 <3 5.5 5.5 1 2
47.3 54.2 29.7 24.1 63 124 8 21 19.2
30.4 42.2 24.3 19.9 45 77.5 8.7 16.1 17.3
24.6 25.5 19.3 13.2 31 58.8 7.8 11.4 13
27.6 26.6 12 9.8 25 43.6 7.5 8.5 9.9
EVALUATION OF PUBERTAL BOYS WITH VARICOCELE
ma1 FSH responses in 3 of 9 suggestive of gonadal damage. Inhibin B levels in each of these individuals remained within normal limits, which suggests that inhibin B may not be an accurate predictor until there is substantial testicular damage in adolescents with varicoceles. A negative correlation between FSH and inhibin B is found in pubertal boys at Tanner stage I11 and is maintained in men.24 Regardless of varicocele size, bilaterally, testicular volume loss or abnormal response to Gn-RH stimulation, the inverse relationship between basal FSH and serum inhibin B tended to be presewed. This intact relationship between FSH and inhibin B as well as the serum inhibin B level in adolescent patients with varicoceles may in fact deteriorate in time, as patient age increases and time to varicocele repair lengthens. We found no correlation among testosterone levels, LH, FSH and inhibin B. Unfortunately our sample size is small and conclusions based on age differences at presentation and interval to varicocele repair cannot be made. CONCLUSIONS
Our results did not demonstrate any abnormalities in serum inhibin B in a model group of adolescents with varicoceles whether there was bilateral, testicular asymmetry or an abnormal response to Gn-RH stimulation. The lack of correlation between inhibin B values and these parameters fails to suggest that inhibin B has a role in the clinical assessment of testicular function in adolescents with varicoceles. Further studies of larger patient populations and normal controls may further elucidate the clinical value of serum inhibin B levels in adolescents with varicoceles. REFERENCES
1. Steeno, O., Knops, J., DecMerck, L., Adimoelja, A. and van de Voorde, H.: Prevention of fertility disorders by detection and treatment varicocele at school and college age. Andrologia, 8 47, 1976. 2. Okuyama, A., Nakamura, M., Takeyama, M., Utsunomiya, M., Fujioka, H., Itatani, H., Matsyda, M., Matsumoyo, K and Sonoda, T.: Surgical repair of varicocele at puberty: preventive treatment for fertility improvement. J . Urol., 139 562, 1988. 3. Hadziselomovic, F., Herzog, B., Liebundgut, B., Jenny, P. and Buser, M.: Testicular and vascular changes in children and adults with varicocele. J . Urol., part 2, 142 583, 1989. 4. Hadziselimovic, F., Herzog, B. and Jenny, P.: The chance for fertility in adolescent boys after corrective surgery for varicocele. J. Urol., 154: 731, 1995. 5. Kass, E. J., Freitas, J . E., Salisz, J . A. and Steinert, B. W.: Pituitary gonadal dysfunction in adolescents with varicocele. Urology, 42: 179, 1993. 6. Parrott, T. S.: Summary of annual meeting of the section on pediatric urology. Pediatrics, 83: 591, 1989. 7. Anawalta, B. D., Bebb, R. A., Matsumoto, A. M., Groome, N. P., Illingworth, P. J., McNeilly, A. S. and Bremner, W. J.: Serum inhibin B levels reflect Sertolli cell function in normal men and men with testicular dysfunction. J . Clin. Endocr. Metab., El: 3341, 1996.
877
8. Burger, H. G.: Clinical review 46: clinical utility of inhibin measurements. J. Clin. Endocr. Metab., 7 6 1391, 1993. 9. Lingh, N., Ying, S. Y., Ueno, N., Shimasaki, S., Esch, F., Hotta, M. and Guillemin, R.: Pituitary FSH is released by a heterodimer of the beta-subunits from the two forms of inhibin. Nature, 321: 779, 1986. 10. Illingworth, P. J., Groome, N. P., Byrd, W., Rainey, W. E., McNeilly, A. S., Mather, J . P. and Bremner, W. J.: Inhibin-B: a likely candidate for the physiologically important form of inhibin in men. J. Clin. Endocr. Metab., El: 1321, 1996. 11. Robertson, D., Burger, H. G., Sullivan, J., Cahir, N., Groome, N., Poncelet, E., Franchimont, P., Woodruff, T. and Mather, J. P.: Biological and immunological characterization of inhibin forms in human plasma. J . Clin. Endocr. Metab., El: 669, 1996. 12. Groome, N. P., Illingworth, P. J., OBrien, M., Pai, R., Rodger, I. E., Mather, J . P. and McNeilly, A. S.: Measurement of dimeric inhibin B throughout the human menstrual cycle. J. Clin. Endocr. Metab., El: 1401, 1996. 13. Marshall, W. A. and Tanner, J. M.: Variations in the pattern of pubertal changes in boys. Arch. Dis. Child., 4 5 13, 1970. 14. Albert, A. A,, Rosemberg, E., Ross, G. T., Paulsen, C. A. and Ryan, R. J.: Report of the National Pituitary Agency collaborative study on the radioimmunoassay of FSH and LH. J. Clin. Endocr. Metab., 2 8 1214, 1968. 15. Korth-Schutz, S., Levine, L. S., and New, M. I.: Serum androgens in normal prepubertal and pubertal children and in children with precocious adrenarche. J . Clin. Endocr. Metab., 4 2 117, 1976. 16. Groome, N. P. and OBrien, M.: Immunoassays for inhibin and its subunits. Further applications of the synthetic peptide approach. J. Immunol. Meth., 165 167, 1993. 17. McCullagh, D. R.: Dual endocrine activity of the testis. Science, 7 6 19, 1932. 18. Seminara, S. B., Boepple, P. A., Nachtigall, L. B., Pralong, F. P., Khoury, R. H., Sluss, P. M., Lecain, A. E. and Crowley, W. F., Jr.: Inhibin B in males with gonadotropin-releasing hormone (GnRH) deficiency: changes in serum concentration after shortterm physiologic GnRH replacement-a clinical research center study. J . Clin. Endocr. Metab., El: 3692, 1996. 19. Reitelman, C., Burbige, K. A,, Sawcuk, I. S. and Hensle, T. W.: Diagnosis and surgical correction of the pediatric varicocele. J. Urol., 138 1038, 1987. 20. Lipshultz, L. I. and Corriere, J . N., Jr.: Progressive testicular atrophy in the varicocele patient. J . Urol., 117: 175, 1977. 21. Kass, E. J. and Belman, A. B.: Reversal of testicular growth failure by varicocele ligation. J. Urol., 137: 475, 1987. 22. Ando, S., Giacchetto, C., Beraldi, E., Panno, M. L., Lombardi, A., Sposato, G. and Golpi, G.: The influence of age on cell Leydig cell function in patients with varicocele. Int. J. Androl., 7: 104, 1982. 23. Hudson, R. W., Perez-Marrero, R. A., Crawford, V. A. and McKay, D. E.: Hormonal parameters of men with varicoceles before and after varicocelectomy. Fertil. Steril., 43:905, 1985. 24. Andersson, A. M., Juul, A., Petersen, J. H., Muller, J., Groome, N. P. and Skakkebaek, N. E.: Serum inhibin B in healthy pubertal and adolescent boys: relation to age, stage of puberty, and follicle stimulating hormone, luteinizing hormone, testosterone, and estradiol levels. J. Clin. Endocr. Metab., 8 2 3976, 1997.
Vol. 162,875-877, September 1999 Printed in U.S.A.
THEJOIJRNAL OF UROLOGY Copyright 0 1999 by AMERICAN UROLOCICAL ASSOCIATION, INC.
SERUM INHIBIN B LEVELS AND THE RESPONSE TO GONADOTROPIN STIMULATION TEST IN PUBERTAL BOYS WITH VARICOCELE ADRIANA CARRILLO, ABBEY GERSHBEIN, KENNETH I. GLASSBERG, AND MARC0 DANON From the Division of Pediatric Urology, State University of New York Downstate Medical Center in Brooklyn and Division of Pediatric Endocrinology, Maimonides Medical Center, Brooklyn, New York and Miami Children's Hospital, Miami, Florida
ABSTRACT
Purpose: The impact of varicoceles on gonadal function in adolescents has been evaluated using several parameters, including size of testes, hormonal levels and provocative endocrine testing. Inhibin B has been demonstrated to be decreased in men with testicular damage from conditions other than varicocele. We determine whether inhibin B levels are low in adolescent boys with varicocele, and if there is a relationship between inhibin B and an exaggerated response to gonadotropin-releasing hormone (Gn-RH) stimulation testing, testicular hypertrophy andor varicocele bilaterality. Materials and Methods: We studied 9 boys at Tanner stages I11 to V of pubertal development who had either left or bilateral varicoceles. Basal inhibin B, follicle-stimulating hormone, luteinizing hormone and testosterone were measured. Each patient underwent Gn-RH stimulation testing. Results: All patients had essentially normal inhibin B levels for Tanner stage. Of the 9 boys 4 had an exaggerated response to Gn-RH stimulating testing. Inhibin B levels did not vary significantly either with the presence of bilateral or unilateral varicoceles or asymmetric testis. Conclusions: The lack of correlation between inhibin B levels and the aforementioned parameters failed to suggest that inhibin B has a significant role in the clinical assessment of testicular function in adolescents with varicocele. Further studies of larger populations may further elucidate the value of inhibin B levels and varicoceles. KEYWORDS:varicocele, gonadotropins, inhibin, puberty
Varicocele is considered the most common identifiable cause of infertility in men and may be present in as many as 15% of boys by age 15 years.' In some cases varicocele can induce changes in testicular growth and histology that may ultimately affect spermatogenesis.2-4 The impact of varicoceles on gonadal function in adolescents has been evaluated using several parameters, including testicular size, hormonal levels and provocative endocrine testing. In adolescents with testicular growth arrest a n exaggerated gonadotropin response to gonadotropin stimulation may be indicative of gonadal damage.5.6 Another potential marker of testicular damage is serum inhibin that is secreted by the Sertoli cells.7.8 Inhibin B has a critical role in folliclestimulating hormone (FSH) regulation via a closed loop negative feedback system.9 Recently, a new highly sensitive assay was developed to differentiate between the biologically inactive inhibin A and the biologically active inhibin B in vitro.10-12 In 1996 Illingworth et a1 demonstrated barely detectable inhibin B levels in men with azoospermia, suggesting that low inhibin B levels correlate with damage asAccepted for publication April 16, 1999.
sociated with infertility.10 Reduced basal serum inhibin levels as well as an exaggerated gonadotropin response to gonadotropin-releasing hormone (Gn-RH) may help to identify which patients would benefit from surgery. We determine whether inhibin B levels are indicative of early testicular damage in adolescents with varicoceles, and whether inhibin levels correlate with response t o Gn-RH stimulation testing, testicular volume loss a n d o r bilaterality. Identifymg an objective means to assess for testicular damage in adolescents with varicoceles may be useful in the decision making process of varicocelectomy. METHODS
Our study included 9 adolescents 12 to 20 years old with either left or bilateral varicoceles diagnosed on routine physical examination. Pubertal development was staged according to Tanner criteria, and all patients were at Tanner stages I11 to V.1" Testicular volume was assessed using a Takihara ring orchidometer (table 1).Testicular asymmetry was considered present when the left testis was at least 3 cc smaller
TABLE1. Tanner stage, testicular volume, levels Pt.No. 1 2 3 4 5 6 7 8 9
Tanner Stage 5 5 5 4 3 5 4 4 3
Rt. Testicle (ml.) 12 20 12 12 15 15 10 10 12
Lt. testicle (ml.) 12 12 12 10 7 15 10 12 14
875
of Inhibin B and testosterone
Varicocele Side Bilat. Lt. Bilat. Bilat. Lt. Lt. Lt . Lt . Bilat.
Inhibin B (pgJml.1 120 102.5 314 349 438 196 177.9 150 156
Testosterone (ng./ml.) 21 112 435 329 372 329 337 68 479
876
EVALUATION OF PUBERTAL BOYS WITH VARICOCELE
than the right testis and its volume was less than 85% of the right side. The Gn-RH stimulation test was performed in a standardized fashion. Blood samples were obtained just before intravenous bolus injection of 100 pg. synthetic Gn-RH, and similar samples were drawn at 30,60,90 and 120 minutes after injection. The normal gonadotropin response to Gn-RH stimulation was calculated by subtracting the baseline (0 minute) value for FSH and luteinizing hormone (LH) from stimulation values (30 and 60 minutes). The maximal normal FSH value 30 and 60 minutes after stimulation was 8.2 mIU. Similarly, the maximal LH response values were 51.7 and 44.1 mIU a t 30 and 60 minutes, re~pectively.~ Serum FSH, LH and testosterone were analyzed by previously described radioimmunoassay techniques.14.l5 The low end LH sensitivity, interassay and intra-assay coefficients of variations were less than 3 mIU/ml., 9.7%and 6.4%,respectively. The low end FSH sensitivity, interassay and intraassay coefficients of variation were 0.3 mIU/ml., 4.7% and less than 3%,respectively. For serum testosterone the lower limit of detection, interassay and intra-assay coefficients of variation were 0.03 ng./ml., 9.9%and 5.9%,respectively. Inhibin B was measured with a double antibody enzyme immunometric assay using ultrasensitive inhibin B kits.16 Patient samples and standards were treated before the enzyme-linked immunosorbent assay (ELISA) with detergent, heated to lOOC and exposed to hydrogen peroxide. These treatments enhanced the specificity and sensitivity of ELISA. Coefficient of variation was less than 5% within plates and less than 7% between plates for both assays. Inhibin B had approximately 1%cross reaction with inhibin A. The detection limit was less than 15 pg./ml. for inhibin B assay. For statistical analysis data are presented as mean plus or minus standard error of mean. The absolute peak value and delta value were used to evaluate the gonadotropin response to Gn-RH test. The delta value was calculated by subtracting the baseline value of FSH and LH from their respective post-stimulation values. The relationships between inhibin B and other hormones were analyzed by forward stepwise multiple linear regression with p < 0.05 considered significant. RESULTS
The individual Tanner Stage, testicular volume, varicocele side, serum inhibin B as well as testosterone are shown in table 1. Mean serum inhibin B level was 231 ? 40 pg./ml. There was no statistically significant relationship when inhibin B levels were correlated with testes size, presence of bilateral varicoceles or response to Gn-RH stimulation testing. Of the 9 patients 4 had abnormal responses to Gn-RH stimulation tests suggestive of testicular dysfunction (table 2). Patients 2 and 6 had an elevated baseline FSH with normal baseline LH but a hyperreactive response for FSH and LH. Patient 5 had normal baseline FSH and LH with an
exaggerated LH response. Patient 7 had normal baseline gonadotropin levels with exaggerated FSH response to Gn-RH stimulation. Mean delta and peak LH values were 42 2 12 and 45 2 11 mIU/ml., respectively. There was no statistically significant correlation among delta LH, testosterone and inhibin B. There was a negative correlation between the peak and delta FSH with basal serum inhibin B (r = -0.47 and r = -0.44). Testosterone levels were not correlated with testicular volume, LH, FSH or inhibin B. Patients 1 and 8 had testosterone levels below what is expected for pubertal stage, suggesting gonadal dysfunction. DISCUSSION
Inhibin is a dimeric glycoprotein secreted by the Sertoli cells738 believed to regulate FSH secretion by a closed loop negative feedback mechanism.9 It was first postulated to exist in the 1920s by McCullagh who named it “the water soluble principle in the testis.”17 Initially, except for hypogonadotropic conditions,l8 there was no evidence to support a variation in inhibin levels when comparing fertile and infertile men which lead some to question the role of inhibin measurements in the clinical setting. Unfortunately, most early studies regarding inhibin are based upon heterologous assays which are not able to distinguish between the a and p forms due to cross-reactivity between the 2 dimers. Using the newer ELISA, Illingworth et a1 in 1996 demonstrated an inverse relationship between inhibin B and FSH concentrations,lO supporting the original hypothesis of McCullagh and demonstrating the critical role that inhibin B has in the regulation of gonadotropin secretion. It seems possible that inhibin B might be a useful marker of Sertoli and/or germ cell function in adolescents with varicoceles. Several authors have sought parameters that may be useful in predicting which adolescents are likely to benefit from varicocele ligation.19-21 Factors such as testicular volume loss, bilateral varicoceles and large varicoceles have served as indications for varicocele ligation in adolescents in whom seminal parameters are usually not available. None of our patients with ipsilateral testicular volume loss demonstrated decreased inhibin B levels. Perhaps the degree of damage to the testes in adolescents with varicoceles and testicular volume loss was not severe enough to affect serum inhibin B values. The Gn-RH stimulation test has been useful in evaluating patients with suspected testicular damage.22 Hudson et a1 studied infertile men with varicoceles and exaggerated gonadotropin responses to Gn-RH stimulation.23 Following varicocele ligation this response as well as spermatogenesis returned to normal. Kass et al reported an abnormal response to Gn-RH stimulation in almost a third of adolescents with varicoceles, an exaggerated LH response suggestive of Leydig cell dysfunction and an exaggerated FSH response suggestive of a defect at the level of the seminiferous tubules5 Similarly to their findings, we also found exaggerated LH response to Gn-RH stimulation in 3 of 9 patients, and abnor-
TABLE2 . FSH and LH responses to Gn-RH test -
FSH (mIU/rnl.)
~~
Pt. No. 1 2 3 4 5 6 7 8 9
LH (mIU/ml.)
0 Min.
30 Mins.
60 Mins.
90 Mins.
120 Mins.
0 Min.
30 Mins.
60 Mins.
90 Mins.
120 Mins.
11.7 25.6 6 2.6 3.7 18.7 3.3 1.5 4.9
19.7 42.7 9.1 3.1 9 33.6 20.6 4.1 8.2
18.5 37.8 9 3.3 9 34.2 18.5 4.2 9.8
17.3 36.3 9.1 3.5 8.5 32.6 12.6 4.2 9.5
18 38.8 8 3.3 8.4 30.3 11.2 3.5 9.2
8.7 5.8 3.5 <3 <3 5.5 5.5 1 2
47.3 54.2 29.7 24.1 63 124 8 21 19.2
30.4 42.2 24.3 19.9 45 77.5 8.7 16.1 17.3
24.6 25.5 19.3 13.2 31 58.8 7.8 11.4 13
27.6 26.6 12 9.8 25 43.6 7.5 8.5 9.9
EVALUATION OF PUBERTAL BOYS WITH VARICOCELE
ma1 FSH responses in 3 of 9 suggestive of gonadal damage. Inhibin B levels in each of these individuals remained within normal limits, which suggests that inhibin B may not be an accurate predictor until there is substantial testicular damage in adolescents with varicoceles. A negative correlation between FSH and inhibin B is found in pubertal boys at Tanner stage I11 and is maintained in men.24 Regardless of varicocele size, bilaterally, testicular volume loss or abnormal response to Gn-RH stimulation, the inverse relationship between basal FSH and serum inhibin B tended to be presewed. This intact relationship between FSH and inhibin B as well as the serum inhibin B level in adolescent patients with varicoceles may in fact deteriorate in time, as patient age increases and time to varicocele repair lengthens. We found no correlation among testosterone levels, LH, FSH and inhibin B. Unfortunately our sample size is small and conclusions based on age differences at presentation and interval to varicocele repair cannot be made. CONCLUSIONS
Our results did not demonstrate any abnormalities in serum inhibin B in a model group of adolescents with varicoceles whether there was bilateral, testicular asymmetry or an abnormal response to Gn-RH stimulation. The lack of correlation between inhibin B values and these parameters fails to suggest that inhibin B has a role in the clinical assessment of testicular function in adolescents with varicoceles. Further studies of larger patient populations and normal controls may further elucidate the clinical value of serum inhibin B levels in adolescents with varicoceles. REFERENCES
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