- Email: [email protected]
17,20-Lyase Deficiency: A Rare Cause of Endocrine Hypertension
Case Report: 1 7 Alpha-Hydroxylase/1 7,20Lyase Deficiency: A Rare Cause of Endocrine Hypertension CEDRIC HERMANS, MD, MRCP,* JEAN-FRAN(:OIS DE PLAEN, MD, t PHILIPPE DE NAYER, MD, PHD,f DOMINIQUE MAlTER, MD, PHD*
ABSTRACT: The co:rnbination of hypertension, hypokalie:rnia, and :male pseudoher:rnaphroditis:rn or a:rnenorrhea :must pro:rnpt a search for a rare adrenal enzy:rnatic defect, 17 a-hydroxylase/ 17,20-lyase deficiency. This is a report of the observation of a :male patient in who:rn this rare deficit was diagnosed in adulthood on the basis of lifelong a:rnbiguous external genitalia, hypogonadis:rn, severe hypertension, bilateral adrenal hyperplasia, and biological :markers evoking an excess of :rnineralocorticoids without hyperaldosteronis:rn. KEY INDEXING TERMS: Steroidenzy:rne deficiency; Male pseudoher:rnaphroditis:rn; Congenital adrenal hyperplasia. [A:rn J Med Sci 1996;312(3):126-129.]
hormone (ACTH) by the pituitary and consequent overproduction of mineralocorticoids (deoxycorticosterone [DOC], corticosterone, 18-hydroxycorticosterone). In most cases, elevated levels of mineralocorticoids give rise to hypertension and hypokaliemia whereas the reduced levels or absence of sex hormones result in sexual infantilism in female patients and ambiguous or female external genitalia (male pseudohermaphroditism) in male patients. In this case, the patient was a genetic male who had a 17 a-hydroxylase/17,20-lyase deficiency that was diagnosed at adulthood. Hormonal studies leading to the recognition of the enzyme deficiency and follow-up under treatment are described and discussed. The patho_physiology, clinical, and genetic aspects of this rare disease are reviewed. Case Report
C
ongenital adrenal hyperplasia (CAH) refers to a group of autosomal recessive disorders caused by a defect in any of the enzymatic steps leading to cortisol production.1 Among them, CAH caused by a 17 a-hydroxylase/17,20-lyase deficiency is a rare, but well-defined syndrome.2- 4 The adrenal steroid 17 a -hydroxylase/17,20-lyase (microsomal cytochrome P450c17) catalyzes two sequential reactions: 17 a-hydroxylation of pregnenolone or progesterone, and C17,20 carbon bond cleavage of the 17 a-hydroxylated products to yield dehydroepiandrosterone (DHEA) and androstenedione, respectively (Figure 1).5 •6 A deficiency of P450c17, which is normally present in both the gonads and the adrenal cortex, 7 leads to impaired biosynthesis of cortisol, androgens, and estrogens, with accompanying hypersecretion of adrenocorticotropic Divisions of • Endocrinology, t N ephrology and tMedical Biochem· istry, Cliniques Universitaires Saint-Luc, Avenue Hippocrate, 1200 Bruxelles, Belgium. Submitted January 4, 1996; accepted March 5, 1996. Correspondence: Dominique Maiter, MD, PhD, Division of Endocrinology, Cliniques Universitaires Saint-Luc, Avenue Hippocrate, UCL Diab 5474, 1200 Brussels, B elgium.
126
A 37 -year-old man was admitted for evaluation of severe hypertension. Study of t he medical history revealed that the patient was born with male pseudohermaphroditism and had operations for hypospadias a nd gynecomastia, for which androgen therapy had been given transiently during childhood. Three years before this current admission, he had a subarachnoid hemorrhage caused by an angioma of the anterior cerebral communicant artery that was successfully clipped. Postoperatively, the patient was found to have persistent hypertension that had been unsatisfactorily treated with a -blockers, diuretics, and tJ-blockers. Investigations had also disclosed a persistent hypokalemia with bilateral adrenal gland en largement, but no definitive diagnosis had been made. The patient was heterosexual, single, and had no children . He described only general weakness and episodic headaches. There was no apparent sexual impairment except for a low volume of sperm. The clinical examination showed tall height (180 em), normal weight (65 kg), small testis volume (1 mL) with a micropenis, sparse axillary and pubic hair, and bilateral frank gynecomastia. While under medical treatment with a I'J-blocker, blood pressure was 150/90 mm Hg while prone and 160/ 100 mm Hg while supine. Analysis of relevant laboratory findings disclosed hypokaliemia (3.4 mmol/ L) with urinary potassium loss (46 mmolfper 24 hours). The aldosterone plasma level, taken while the patient was in a lying position and on a reduced salt diet, was low (0.09 nmol/L; normal values, 0.10- 0.40 nmol/L), as was plasma renin activity ( < 0.2 ng/ mL/ h; normal values, 0.9-0.2 ng/ mL/h). Additional endocrine testing was performed and the results showed hypogonadism (total testosterone, 6.8 nmol/L; normal values, 13- 35 nmol/L), with high luteinizing hormone levels (9.9 mUI/ mL; normal values, 1- 8 mUI/mL) and follicle stimulating hormone levels (19.7 mUI/mL; normal values, September 1996 Volume 312 Number 3
Hermans et al
stllnding I lying : 0.06510.09 { 0 .1· 0.4)
Figure 1. Plasma levels of the main steroids in the propositus, normal values (in parentheses), and principal steroid biosynthesis pathways. Cytochrome P450scc converts cholesterol to pregnenolone by catalyzing 20 a-hydroxylation, 22-hydroxylation and scission of the C20-22 bond. P450c17 mediates both 17 a-hydroxylation of pregnenolone and progesterone and 17,20-lyase activity for !?-hydroxyprogesterone and 17-hydroxypregnenolone. 3 /1-hydroxysteroid deshydrogenase (3 Beta-HSD) catalyzes both dehydrogenation of the 3-hydroxyl group and isomerization of the double bond at C-5 of pregnenolone and androstenedione leading to progesterone and androstenedione. P450c21 catalyzes 21-hydroxylation of progesterone to deoxycorticosterone (DOC) and of 17-hydroxyprogesterone to 11deoxycortisol. P450cll catalyzes three clearly distinguishable reactions: 11 beta-hydroxylase, IS-hydroxylase and 18-methyl oxidase, converting DOC to aldosterone and 11-deoxycortisol to cortisol. Low levels of sex steroids and increased mineralocorticoid precursors are suggestive of a 17 a-hydroxylase/17,20-lyase deficiency. • All values are shown in nmoi/L, except DHEA-S in ~tmol/L .
1- 8 mUI/ mL) . Plasma levels of the principal steroids are shown in Figure 1, which also illustrates the main steroid biosynthesis pathways. These results revealed a typical block in 17 a-hydroxylase/ 17,20-lyase activity with increased levels of compounds above the block (progesterone, 17-0H-progesterone, deoxycorticosterone and corticosterone) and decreased levels of downstream hormones (cortisol , DHEA, androstenedione). As illustrated in Table 1, administration of exogenous ACTH did not elicit any significant rise in 170H-progesterone, DHEA, or cortisol levels, but increased plasma deoxycorticosterone concentration. Computed tomograph scanning of the abdomen confirmed bilateral adrenal hyperplasia. The patient was placed on continuous treatment with oral dexamethasone at bedtime (0.375-0.500 mg/d) and intramuscular testosterone monthly. Spironolactone treatment was given temporarily. Most clinical and biochemical parameters were normalized during the follow-up visits, as summarized in Table 2.
Discussion
The most prominent features of mineralocorticoid excess are hypertension with hypokaliemia and inappropriate urinary loss of potassium. The diagnosis of primary hyperaldosteronism can be easily delineated on the basis of increased plasma and urinary aldosterone and suppressed plasma renin activity. In rare instances, aldosterone levels are low or normal despite apparent mineralocorticoid excess. In such cases, liquorice or 9 a-ftuorohydrocortisone consumption should THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES
first be ruled out by carefully taking the patient's history. Excessive production of aldosterone precursors with mineralocorticoid activity needs also to be considered and is often secondary to adrenal enzymatic defects. Indeed, hypertension with hypokaliemia is usual in defects of 11 ~-hydroxylase (P450c11) or 17 a-hydroxylase/17,20-lyase. 1 P450c11 mediates the ~ hydroxylation of 11-deoxycortisol to cortisol and the final steps in the synthesis of aldosterone from DOC (Figure 1). Thus, P450c11 deficiency results in DOC overproduction and androgen excess that leads to pseudohermaphroditism in female patients and precocious virilization in male patients. In contrast, low levels of androgens (DHEA, androstenedione) combined with high levels of mineralocorticoid precursors (DOC, corticosterone and their 18-hydroxylated products) should evoke deficient P450c17 activity. The deficiency of 17 a-hydroxylase/17,20-lyase is a rare form of CAH. Since the first description by Biglieri et al, 2 more than 120 cases of 17 a-hydroxylase/17,20lyase deficiency have been described clinically and hormonally, with the majority as genetically male patients. The enzymes 17 a-hydroxylase and 17 ,20-lyase were initially thought to be different enzymes, in part because of reports of isolated 17,20-lyase deficiency. 8 However, it is now established that a single enzyme catalyzes both reactions and that a defect on a single polypeptide is responsible for the molecular basis of deficiencies in both 17 a-hydroxylase and 17,20-lyase.5 •6 In addition, 17 a-hydroxylase/17,20-lyase activity is present in both the adrenals and the gonads, 9 •10 as opposed to 21 a-hydroxylase and 11 a-hydroxylase that show adrenal-specific expression. The enzymatic defect is therefore also present in the gonads where the production of sex hormones is impaired. The main clinical feature of the disease is hypertension caused by an excessive production of potent mineralocorticoids (corticosterone, DOC, and 18 hydroxylated compounds), whereas the level of aldosterone is low because of a reversible suppression of the reninangiotensin-aldosterone system, secondary to the expansion of the extracellular fluids and blood volumes caused by the mineralocorticoids excess.U The onset and natural history of hypertension are not well described.8 The diagnosis is usually made around puberty, and the degree of hypertension varies from mild to seTable 1. Response of Adrenal Steroids to Exogenous ACTH Administration (250 !Lg Intravenously at 8 am)
Cortisol (nmol/ L) 17-0H-progesterone (nmoi/L) DHEA (nmoi/L) !!-deoxycorticosterone (nmoi/L)
TimeO'
Time 60'
210 38 0.8 2.6
172 26.4
ACTH = adrenocorticotropic hormone; DHEA terone.
=
1.9 13.7
dehydroepiandroes-
127
17 Alpha-Hydroxylase/17,20-Lyase Deficiency
Table 2. E volut ion of Blood Pressure , Pot assium Levels a nd H ormonal Values Under Treat ment Follow-Up (Mos) P a ra meters Blood pressure (mm Hg) Potassium (mmol/ L) 17 OH·progesterone (nmol/L) DOC (nmol/ L ) Cort icosterone (nmol/L ) PRA ( ~I g/L/h ) ACTH (ng/L) T otal testosterone (nmol/L) Treatment Dexamethasone (mg/day) S p ironolactone (mg/day) T estosteron e (mg)
3
6
135/85 3.9 22.2
135/90 4.6 23.9
232 6.8 17 6
107 10.1 8 9.7
0.375 25 100/2 wks
0.375 250/4 wks
12
24
140/ 90 3.6 25.6 0.7 12 6.4 2 13.1
130/80 4.1 27.5 1.3 15 11.3 5 6.3
0.50
0.50
250/3 wks
100/3 wks*
* The dosage of testosterone was reduced by the patient because of subjective side effects (dizziness and irritability). D OC = deoxycorticosterone; PRA =plasma renin activity; A CTH = adrenocorticotropic hormone.
vere. 8 The patient's situation described here is unusual in t his regard, as diagnosis of severe and complicated endocrine hypertension was made only at adulthood. In genetic males, absence of masculinization is usual. If there is no production of testosterone, the external genitalia can be phenotypically completely female. However, normal, infantile, or ambiguous external genitalia have been reported, which suggests some degree of testosterone production in a subset of male patients. 8•10 Genetic females with complete enzyme deficiency have primary amenorrhea and no pubertal development, 8 •10 whereas normal or irregular menstruation can occur in milder forms of the disease when estrogens are still produced. There seems to be no constant correlation between the severity of hypertension and the degree of gonadal insufficiency.8 As a consequence of sex steroid deficiency, tallness, delayed skeletal maturation, and osteoporosis are frequent complications during adulthood. 8 As in this patient, clinical evidence of glucocorticoid deficiency is unusual because cortisol is still produced and corticosterone has a weak glucocorticoid activity.8 •10 Genetically, unlike 21 a-hydroxylase deficiency, 17 a-hydroxylase deficiency is not linked to human leukocyte antigens 12 but still follows an autosomal recessive inheritance pattern. The human gene has been mapped to chromosome 10 (10q24-q25) 13 •14 and consists of 8 exons and 7 introns. 15 •16 Different mutations with varying severity of symptoms have been identified and are listed in Table 3.8 •17- 19 The most severe mutations result in truncated proteins with complete loss of function. Six of the 16 known lesions lie in the region of exon 8, coding for the carboxy-terminal end of the polypeptide, and therefore underlie the functional importance of this carboxy-terminal region for enzyme activity. The genetic defect has not yet been uncovered in this patient. · The treatment of 17 a-hydroxylase/17,20-lyase deficiency is essentially the same as that for other types
128
of CAH. Treatment with dexamethasone should not only replace the deficiency in cortisol but should also suppress ACTH and mineralocorticoid overproduction. After transient spironolactone treatment in this patient, blood pressure remained normal with increased plasma renin activity and normal mineralocorticoid precursors under a low dose of dexamethasone. Aldosterone synthesis was functionally suppressed, but levels rose with treatment. Levels of 17-0H-progesterone decreased but remained elevated despite successful suppressive therapy, and therefore suggests a more severe defect in 17,20-lyase than in 17 a-hydroxylase in the patient. Conclusion
Study of this patient emphasizes that CAH is not only a paediatric disease and that 17 a-hydroxylase/ 17,20-lyase deficiency needs to be ruled out by appro-
Table 3. Mutations Responsible for 17 Alpha-Hydroxylase/17,20L yase Deficiency a nd Chromosomal Localization
Non sen se mutations
Deletion s
Duplicat ions Other mutation s
Mutation s
Ex on
Trp17 > stop Arg239 > stop a nd Pro342 > Thr Arg496 > Cys and Gln461 > stop Gln194 > stop and Arg239 > stop Cys442 > stop Phe53/54 518Bp deletion - 469Bp insertion Asp487-Ser488-Phe489 4 Bp duplication codon 480 7 Bp duplication codon 120 His373 > Leu Ser106 > Pro Arg440 > His
1 4, 6 8, 8 3, 4 8 1 2, 3 8 8 2 6 2 8
Trp = tryptophan; Arg =arginine; Pro = proline; Thr = threonine; Cys = cysteine; Gln = glutamine; Phe = phenylalanine; Bp = basepair; A sp = aspartic acid; S er = serine; His = histidine; Leu = leucine. September 1996 Volume 312 Number 3
Hermans et al
priate hormonal studies either in young adult hypertensive male patients with a history of ambiguous or female external genitalia, or in young female patients with sexual infantilism and hypertension. References 1. Miller WL. Congenital adrenal hyperplasia. Endocrinol Metab Clin North Am. 1991 ;20:721-49. 2. Biglieri EG, Herron MA, Brust N. 17-hydroxylation defi· ciency in man . J Clin Invest. 1966;45:1946-54. 3. New MI. Male pseudohermaphroditism due to 17 alpha-hydroxylase deficiency. J Clin Invest. 1970;49:1930- 41. 4. Goldsmith 0, Salomon DH, Horton R. Hypogonadism and mineralocorticoid excess. The 17-hydroxylase deficiency syndrome. N Eng! J Med. 1967;277:673-77. 5. Nakajin S, Shinoda M, Haniu M, Shively JE, Hall PF. C21 steroid side chain cleavage enzyme from porcine adrenal microsomes. Purification and characterization of the 17 alphahydroxylase/C17,20-lyase cytochrome P-450. J Bioi Chern. 1984;259:3971- 76. 6. Zuber MX, Simpson ER, Waterman MR. Expression of bovine 17 alpha -hydroxylase cytochrome P-450 eDNA in Nonsteroidogenic (Cos 1) cells. Science. 1986;234:1258- 61. 7. Chung B-C, Picado-Leonard J, Haniu M, Bienkowski M, Hall PF, Shively JE, et al. Cytochrome P450c17 (steroid 17 alpha-hydroxylase/17,20-lyase) : Cloning of human adrenal and testis cDNAs indicates the same gene is expressed in both tissues. Proc Nat! Acad Sci US A. 1987;84:407- 11. 8. Yanase T, Simpson ER, Waterman MR. 17 alpha-hydroxylase/ 17,20-lyase deficiency: from clinical investigation to molecular definition. Endocr Rev. 1991;12:91- 108. 9. Miller WL. Molecular biology of steroid hormones synthesis. Endocr Rev. 1988;9:295-318. 10. Kater CE, Biglieri EG. Disorders of steroid 17 alpha-hydroxylase deficiency. Endocrinol Metab Clin North Am. 1994;23:34157.
THE AMERICAN
~OURNAL
OF THE MEDICAL SCIENCES
11. Kater CE, Biglieri EG, Brust N, Chang B, Hirai J. The unique patterns of plasma aldosterone and 18 hydroxycorticosterone concentrations in the 17 alpha-hydroxylase deficiency syndrome. J Clin Endocrinol Metab. 1982;55:295- 302. 12. D' Armiento M, Reda G, Bisignani G, Tabolli S, Cappellaci S, Lulli P. No linkage between HLA and congenital adrenal hyperplasia due to 17 alpha-hydroxylase deficiency. N Eng! J Med. 1983;308:970-71. 13. Matteson KJ, Picado-Leonard J, Chung B-C, Mohandas TK, Miller WL. Assignment of the gene for adrenal P450c17 (steroid 17 alpha-hydroxylase/17,20-lyase) to human chromosome 10. J Clin Endocrinol Metab. 1986;63:789-91. 14. Sparkes RS, Klisak I, Miller WL. Regional mapping of genes encoding human steroidogenic enzymes P450scc to 15q23-q24, adrenodoxin to llq22; adrenodoxin reductase to 17q24-q25; and P450c17 to 10q24- q25. DNA Cell Bioi. 1991;10:359-65. 15. Picado-Leonard J, Miller WL. Cloning and sequence of the human gene for P450C17 (steroid 17 alpha-hydroxylase/17,20lyase): similarity with the gene for P450C21. DNA. 1987;6:43948. 16. Kagimoto M, Winter JSD, Kagimoto K, Simpson ER, Waterman MR. Structural characterization of normal and mutant human steroid 17 alpha-hydroxylase genes: molecular basis of one example of combined 17 alpha-hydroxylase/17,20lyase deficiency. Mol Endocrinol. 1988;2:564-70. 17. Rumsby G, Skinner C, Lee HA, Honour JW. Combined 17 alpha-hydroxylase/17,20-lyase deficiency caused by heterozygous stop codons in the cytochromes P450 17 alpha-hydroxylase gene. Clin Endocrinol. 1993;39:483-85. 18. Fardella CE, Hum DW, Homoki J, Willer WL. Point mutation of Arg440 to His in Cytochrome P450c17 causes severe 17 alpha-hydroxylase deficiency. J Clin Endocrinol Metab. 1994;79:160-64. 19. Oshiro C, Takasu N, Wakugami T, Komiya I, Yamada T, Eguchi Y, et al. Seventeen alpha-hydroxylase deficiency with one base-pair deletion of the cytochrome P450c17 gene. J Clin Endocrinol Metab. 1995;80:2526-29.
129
ABSTRACT: The co:rnbination of hypertension, hypokalie:rnia, and :male pseudoher:rnaphroditis:rn or a:rnenorrhea :must pro:rnpt a search for a rare adrenal enzy:rnatic defect, 17 a-hydroxylase/ 17,20-lyase deficiency. This is a report of the observation of a :male patient in who:rn this rare deficit was diagnosed in adulthood on the basis of lifelong a:rnbiguous external genitalia, hypogonadis:rn, severe hypertension, bilateral adrenal hyperplasia, and biological :markers evoking an excess of :rnineralocorticoids without hyperaldosteronis:rn. KEY INDEXING TERMS: Steroidenzy:rne deficiency; Male pseudoher:rnaphroditis:rn; Congenital adrenal hyperplasia. [A:rn J Med Sci 1996;312(3):126-129.]
hormone (ACTH) by the pituitary and consequent overproduction of mineralocorticoids (deoxycorticosterone [DOC], corticosterone, 18-hydroxycorticosterone). In most cases, elevated levels of mineralocorticoids give rise to hypertension and hypokaliemia whereas the reduced levels or absence of sex hormones result in sexual infantilism in female patients and ambiguous or female external genitalia (male pseudohermaphroditism) in male patients. In this case, the patient was a genetic male who had a 17 a-hydroxylase/17,20-lyase deficiency that was diagnosed at adulthood. Hormonal studies leading to the recognition of the enzyme deficiency and follow-up under treatment are described and discussed. The patho_physiology, clinical, and genetic aspects of this rare disease are reviewed. Case Report
C
ongenital adrenal hyperplasia (CAH) refers to a group of autosomal recessive disorders caused by a defect in any of the enzymatic steps leading to cortisol production.1 Among them, CAH caused by a 17 a-hydroxylase/17,20-lyase deficiency is a rare, but well-defined syndrome.2- 4 The adrenal steroid 17 a -hydroxylase/17,20-lyase (microsomal cytochrome P450c17) catalyzes two sequential reactions: 17 a-hydroxylation of pregnenolone or progesterone, and C17,20 carbon bond cleavage of the 17 a-hydroxylated products to yield dehydroepiandrosterone (DHEA) and androstenedione, respectively (Figure 1).5 •6 A deficiency of P450c17, which is normally present in both the gonads and the adrenal cortex, 7 leads to impaired biosynthesis of cortisol, androgens, and estrogens, with accompanying hypersecretion of adrenocorticotropic Divisions of • Endocrinology, t N ephrology and tMedical Biochem· istry, Cliniques Universitaires Saint-Luc, Avenue Hippocrate, 1200 Bruxelles, Belgium. Submitted January 4, 1996; accepted March 5, 1996. Correspondence: Dominique Maiter, MD, PhD, Division of Endocrinology, Cliniques Universitaires Saint-Luc, Avenue Hippocrate, UCL Diab 5474, 1200 Brussels, B elgium.
126
A 37 -year-old man was admitted for evaluation of severe hypertension. Study of t he medical history revealed that the patient was born with male pseudohermaphroditism and had operations for hypospadias a nd gynecomastia, for which androgen therapy had been given transiently during childhood. Three years before this current admission, he had a subarachnoid hemorrhage caused by an angioma of the anterior cerebral communicant artery that was successfully clipped. Postoperatively, the patient was found to have persistent hypertension that had been unsatisfactorily treated with a -blockers, diuretics, and tJ-blockers. Investigations had also disclosed a persistent hypokalemia with bilateral adrenal gland en largement, but no definitive diagnosis had been made. The patient was heterosexual, single, and had no children . He described only general weakness and episodic headaches. There was no apparent sexual impairment except for a low volume of sperm. The clinical examination showed tall height (180 em), normal weight (65 kg), small testis volume (1 mL) with a micropenis, sparse axillary and pubic hair, and bilateral frank gynecomastia. While under medical treatment with a I'J-blocker, blood pressure was 150/90 mm Hg while prone and 160/ 100 mm Hg while supine. Analysis of relevant laboratory findings disclosed hypokaliemia (3.4 mmol/ L) with urinary potassium loss (46 mmolfper 24 hours). The aldosterone plasma level, taken while the patient was in a lying position and on a reduced salt diet, was low (0.09 nmol/L; normal values, 0.10- 0.40 nmol/L), as was plasma renin activity ( < 0.2 ng/ mL/ h; normal values, 0.9-0.2 ng/ mL/h). Additional endocrine testing was performed and the results showed hypogonadism (total testosterone, 6.8 nmol/L; normal values, 13- 35 nmol/L), with high luteinizing hormone levels (9.9 mUI/ mL; normal values, 1- 8 mUI/mL) and follicle stimulating hormone levels (19.7 mUI/mL; normal values, September 1996 Volume 312 Number 3
Hermans et al
stllnding I lying : 0.06510.09 { 0 .1· 0.4)
Figure 1. Plasma levels of the main steroids in the propositus, normal values (in parentheses), and principal steroid biosynthesis pathways. Cytochrome P450scc converts cholesterol to pregnenolone by catalyzing 20 a-hydroxylation, 22-hydroxylation and scission of the C20-22 bond. P450c17 mediates both 17 a-hydroxylation of pregnenolone and progesterone and 17,20-lyase activity for !?-hydroxyprogesterone and 17-hydroxypregnenolone. 3 /1-hydroxysteroid deshydrogenase (3 Beta-HSD) catalyzes both dehydrogenation of the 3-hydroxyl group and isomerization of the double bond at C-5 of pregnenolone and androstenedione leading to progesterone and androstenedione. P450c21 catalyzes 21-hydroxylation of progesterone to deoxycorticosterone (DOC) and of 17-hydroxyprogesterone to 11deoxycortisol. P450cll catalyzes three clearly distinguishable reactions: 11 beta-hydroxylase, IS-hydroxylase and 18-methyl oxidase, converting DOC to aldosterone and 11-deoxycortisol to cortisol. Low levels of sex steroids and increased mineralocorticoid precursors are suggestive of a 17 a-hydroxylase/17,20-lyase deficiency. • All values are shown in nmoi/L, except DHEA-S in ~tmol/L .
1- 8 mUI/ mL) . Plasma levels of the principal steroids are shown in Figure 1, which also illustrates the main steroid biosynthesis pathways. These results revealed a typical block in 17 a-hydroxylase/ 17,20-lyase activity with increased levels of compounds above the block (progesterone, 17-0H-progesterone, deoxycorticosterone and corticosterone) and decreased levels of downstream hormones (cortisol , DHEA, androstenedione). As illustrated in Table 1, administration of exogenous ACTH did not elicit any significant rise in 170H-progesterone, DHEA, or cortisol levels, but increased plasma deoxycorticosterone concentration. Computed tomograph scanning of the abdomen confirmed bilateral adrenal hyperplasia. The patient was placed on continuous treatment with oral dexamethasone at bedtime (0.375-0.500 mg/d) and intramuscular testosterone monthly. Spironolactone treatment was given temporarily. Most clinical and biochemical parameters were normalized during the follow-up visits, as summarized in Table 2.
Discussion
The most prominent features of mineralocorticoid excess are hypertension with hypokaliemia and inappropriate urinary loss of potassium. The diagnosis of primary hyperaldosteronism can be easily delineated on the basis of increased plasma and urinary aldosterone and suppressed plasma renin activity. In rare instances, aldosterone levels are low or normal despite apparent mineralocorticoid excess. In such cases, liquorice or 9 a-ftuorohydrocortisone consumption should THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES
first be ruled out by carefully taking the patient's history. Excessive production of aldosterone precursors with mineralocorticoid activity needs also to be considered and is often secondary to adrenal enzymatic defects. Indeed, hypertension with hypokaliemia is usual in defects of 11 ~-hydroxylase (P450c11) or 17 a-hydroxylase/17,20-lyase. 1 P450c11 mediates the ~ hydroxylation of 11-deoxycortisol to cortisol and the final steps in the synthesis of aldosterone from DOC (Figure 1). Thus, P450c11 deficiency results in DOC overproduction and androgen excess that leads to pseudohermaphroditism in female patients and precocious virilization in male patients. In contrast, low levels of androgens (DHEA, androstenedione) combined with high levels of mineralocorticoid precursors (DOC, corticosterone and their 18-hydroxylated products) should evoke deficient P450c17 activity. The deficiency of 17 a-hydroxylase/17,20-lyase is a rare form of CAH. Since the first description by Biglieri et al, 2 more than 120 cases of 17 a-hydroxylase/17,20lyase deficiency have been described clinically and hormonally, with the majority as genetically male patients. The enzymes 17 a-hydroxylase and 17 ,20-lyase were initially thought to be different enzymes, in part because of reports of isolated 17,20-lyase deficiency. 8 However, it is now established that a single enzyme catalyzes both reactions and that a defect on a single polypeptide is responsible for the molecular basis of deficiencies in both 17 a-hydroxylase and 17,20-lyase.5 •6 In addition, 17 a-hydroxylase/17,20-lyase activity is present in both the adrenals and the gonads, 9 •10 as opposed to 21 a-hydroxylase and 11 a-hydroxylase that show adrenal-specific expression. The enzymatic defect is therefore also present in the gonads where the production of sex hormones is impaired. The main clinical feature of the disease is hypertension caused by an excessive production of potent mineralocorticoids (corticosterone, DOC, and 18 hydroxylated compounds), whereas the level of aldosterone is low because of a reversible suppression of the reninangiotensin-aldosterone system, secondary to the expansion of the extracellular fluids and blood volumes caused by the mineralocorticoids excess.U The onset and natural history of hypertension are not well described.8 The diagnosis is usually made around puberty, and the degree of hypertension varies from mild to seTable 1. Response of Adrenal Steroids to Exogenous ACTH Administration (250 !Lg Intravenously at 8 am)
Cortisol (nmol/ L) 17-0H-progesterone (nmoi/L) DHEA (nmoi/L) !!-deoxycorticosterone (nmoi/L)
TimeO'
Time 60'
210 38 0.8 2.6
172 26.4
ACTH = adrenocorticotropic hormone; DHEA terone.
=
1.9 13.7
dehydroepiandroes-
127
17 Alpha-Hydroxylase/17,20-Lyase Deficiency
Table 2. E volut ion of Blood Pressure , Pot assium Levels a nd H ormonal Values Under Treat ment Follow-Up (Mos) P a ra meters Blood pressure (mm Hg) Potassium (mmol/ L) 17 OH·progesterone (nmol/L) DOC (nmol/ L ) Cort icosterone (nmol/L ) PRA ( ~I g/L/h ) ACTH (ng/L) T otal testosterone (nmol/L) Treatment Dexamethasone (mg/day) S p ironolactone (mg/day) T estosteron e (mg)
3
6
135/85 3.9 22.2
135/90 4.6 23.9
232 6.8 17 6
107 10.1 8 9.7
0.375 25 100/2 wks
0.375 250/4 wks
12
24
140/ 90 3.6 25.6 0.7 12 6.4 2 13.1
130/80 4.1 27.5 1.3 15 11.3 5 6.3
0.50
0.50
250/3 wks
100/3 wks*
* The dosage of testosterone was reduced by the patient because of subjective side effects (dizziness and irritability). D OC = deoxycorticosterone; PRA =plasma renin activity; A CTH = adrenocorticotropic hormone.
vere. 8 The patient's situation described here is unusual in t his regard, as diagnosis of severe and complicated endocrine hypertension was made only at adulthood. In genetic males, absence of masculinization is usual. If there is no production of testosterone, the external genitalia can be phenotypically completely female. However, normal, infantile, or ambiguous external genitalia have been reported, which suggests some degree of testosterone production in a subset of male patients. 8•10 Genetic females with complete enzyme deficiency have primary amenorrhea and no pubertal development, 8 •10 whereas normal or irregular menstruation can occur in milder forms of the disease when estrogens are still produced. There seems to be no constant correlation between the severity of hypertension and the degree of gonadal insufficiency.8 As a consequence of sex steroid deficiency, tallness, delayed skeletal maturation, and osteoporosis are frequent complications during adulthood. 8 As in this patient, clinical evidence of glucocorticoid deficiency is unusual because cortisol is still produced and corticosterone has a weak glucocorticoid activity.8 •10 Genetically, unlike 21 a-hydroxylase deficiency, 17 a-hydroxylase deficiency is not linked to human leukocyte antigens 12 but still follows an autosomal recessive inheritance pattern. The human gene has been mapped to chromosome 10 (10q24-q25) 13 •14 and consists of 8 exons and 7 introns. 15 •16 Different mutations with varying severity of symptoms have been identified and are listed in Table 3.8 •17- 19 The most severe mutations result in truncated proteins with complete loss of function. Six of the 16 known lesions lie in the region of exon 8, coding for the carboxy-terminal end of the polypeptide, and therefore underlie the functional importance of this carboxy-terminal region for enzyme activity. The genetic defect has not yet been uncovered in this patient. · The treatment of 17 a-hydroxylase/17,20-lyase deficiency is essentially the same as that for other types
128
of CAH. Treatment with dexamethasone should not only replace the deficiency in cortisol but should also suppress ACTH and mineralocorticoid overproduction. After transient spironolactone treatment in this patient, blood pressure remained normal with increased plasma renin activity and normal mineralocorticoid precursors under a low dose of dexamethasone. Aldosterone synthesis was functionally suppressed, but levels rose with treatment. Levels of 17-0H-progesterone decreased but remained elevated despite successful suppressive therapy, and therefore suggests a more severe defect in 17,20-lyase than in 17 a-hydroxylase in the patient. Conclusion
Study of this patient emphasizes that CAH is not only a paediatric disease and that 17 a-hydroxylase/ 17,20-lyase deficiency needs to be ruled out by appro-
Table 3. Mutations Responsible for 17 Alpha-Hydroxylase/17,20L yase Deficiency a nd Chromosomal Localization
Non sen se mutations
Deletion s
Duplicat ions Other mutation s
Mutation s
Ex on
Trp17 > stop Arg239 > stop a nd Pro342 > Thr Arg496 > Cys and Gln461 > stop Gln194 > stop and Arg239 > stop Cys442 > stop Phe53/54 518Bp deletion - 469Bp insertion Asp487-Ser488-Phe489 4 Bp duplication codon 480 7 Bp duplication codon 120 His373 > Leu Ser106 > Pro Arg440 > His
1 4, 6 8, 8 3, 4 8 1 2, 3 8 8 2 6 2 8
Trp = tryptophan; Arg =arginine; Pro = proline; Thr = threonine; Cys = cysteine; Gln = glutamine; Phe = phenylalanine; Bp = basepair; A sp = aspartic acid; S er = serine; His = histidine; Leu = leucine. September 1996 Volume 312 Number 3
Hermans et al
priate hormonal studies either in young adult hypertensive male patients with a history of ambiguous or female external genitalia, or in young female patients with sexual infantilism and hypertension. References 1. Miller WL. Congenital adrenal hyperplasia. Endocrinol Metab Clin North Am. 1991 ;20:721-49. 2. Biglieri EG, Herron MA, Brust N. 17-hydroxylation defi· ciency in man . J Clin Invest. 1966;45:1946-54. 3. New MI. Male pseudohermaphroditism due to 17 alpha-hydroxylase deficiency. J Clin Invest. 1970;49:1930- 41. 4. Goldsmith 0, Salomon DH, Horton R. Hypogonadism and mineralocorticoid excess. The 17-hydroxylase deficiency syndrome. N Eng! J Med. 1967;277:673-77. 5. Nakajin S, Shinoda M, Haniu M, Shively JE, Hall PF. C21 steroid side chain cleavage enzyme from porcine adrenal microsomes. Purification and characterization of the 17 alphahydroxylase/C17,20-lyase cytochrome P-450. J Bioi Chern. 1984;259:3971- 76. 6. Zuber MX, Simpson ER, Waterman MR. Expression of bovine 17 alpha -hydroxylase cytochrome P-450 eDNA in Nonsteroidogenic (Cos 1) cells. Science. 1986;234:1258- 61. 7. Chung B-C, Picado-Leonard J, Haniu M, Bienkowski M, Hall PF, Shively JE, et al. Cytochrome P450c17 (steroid 17 alpha-hydroxylase/17,20-lyase) : Cloning of human adrenal and testis cDNAs indicates the same gene is expressed in both tissues. Proc Nat! Acad Sci US A. 1987;84:407- 11. 8. Yanase T, Simpson ER, Waterman MR. 17 alpha-hydroxylase/ 17,20-lyase deficiency: from clinical investigation to molecular definition. Endocr Rev. 1991;12:91- 108. 9. Miller WL. Molecular biology of steroid hormones synthesis. Endocr Rev. 1988;9:295-318. 10. Kater CE, Biglieri EG. Disorders of steroid 17 alpha-hydroxylase deficiency. Endocrinol Metab Clin North Am. 1994;23:34157.
THE AMERICAN
~OURNAL
OF THE MEDICAL SCIENCES
11. Kater CE, Biglieri EG, Brust N, Chang B, Hirai J. The unique patterns of plasma aldosterone and 18 hydroxycorticosterone concentrations in the 17 alpha-hydroxylase deficiency syndrome. J Clin Endocrinol Metab. 1982;55:295- 302. 12. D' Armiento M, Reda G, Bisignani G, Tabolli S, Cappellaci S, Lulli P. No linkage between HLA and congenital adrenal hyperplasia due to 17 alpha-hydroxylase deficiency. N Eng! J Med. 1983;308:970-71. 13. Matteson KJ, Picado-Leonard J, Chung B-C, Mohandas TK, Miller WL. Assignment of the gene for adrenal P450c17 (steroid 17 alpha-hydroxylase/17,20-lyase) to human chromosome 10. J Clin Endocrinol Metab. 1986;63:789-91. 14. Sparkes RS, Klisak I, Miller WL. Regional mapping of genes encoding human steroidogenic enzymes P450scc to 15q23-q24, adrenodoxin to llq22; adrenodoxin reductase to 17q24-q25; and P450c17 to 10q24- q25. DNA Cell Bioi. 1991;10:359-65. 15. Picado-Leonard J, Miller WL. Cloning and sequence of the human gene for P450C17 (steroid 17 alpha-hydroxylase/17,20lyase): similarity with the gene for P450C21. DNA. 1987;6:43948. 16. Kagimoto M, Winter JSD, Kagimoto K, Simpson ER, Waterman MR. Structural characterization of normal and mutant human steroid 17 alpha-hydroxylase genes: molecular basis of one example of combined 17 alpha-hydroxylase/17,20lyase deficiency. Mol Endocrinol. 1988;2:564-70. 17. Rumsby G, Skinner C, Lee HA, Honour JW. Combined 17 alpha-hydroxylase/17,20-lyase deficiency caused by heterozygous stop codons in the cytochromes P450 17 alpha-hydroxylase gene. Clin Endocrinol. 1993;39:483-85. 18. Fardella CE, Hum DW, Homoki J, Willer WL. Point mutation of Arg440 to His in Cytochrome P450c17 causes severe 17 alpha-hydroxylase deficiency. J Clin Endocrinol Metab. 1994;79:160-64. 19. Oshiro C, Takasu N, Wakugami T, Komiya I, Yamada T, Eguchi Y, et al. Seventeen alpha-hydroxylase deficiency with one base-pair deletion of the cytochrome P450c17 gene. J Clin Endocrinol Metab. 1995;80:2526-29.
129