17-Hydroxylase Deficiency Syndrome

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17-Hydroxylase (17-OH) deficiency syndrome is a rare genetic disorder of steroid biosynthesis that causes decreased production of glucocorticoids and sex steroids and increased synthesis of mineralocorticoid precursors. It is a rare form of congenital adrenal hyperplasia resulting from loss-of-function mutations involving the CYP17 gene.

This syndrome is characterized by both of the following:

Patients are usually diagnosed with this condition during an evaluation of delayed puberty, absent secondary sexual characteristics, or primary amenorrhea. Although patients with 17-hydroxylase deficiency are cortisol deficient, they do not typically have adrenal insufficiency or experience adrenal crises. Precursor hormones such as corticosterone are elevated, have glucocorticoid activity, and are adequate to prevent adrenal insufficiency.

Exogenous glucocorticoid therapy is the treatment of choice and suppresses adrenocorticotropic hormone (ACTH) secretion, decreases 11-DOC and corticosterone levels, and normalizes serum potassium and blood pressure. Some patients may have persistent hypertension and require additional antihypertension therapy. Prognosis is generally good-to-excellent with adequate glucocorticoid therapy and monitoring.

At puberty, patients require sex steroid replacement for development of secondary sexual characteristics as well as cyclic menstrual bleeding in 46,XX females.

Anatomically, the adrenal gland can be divided into the following 3 zones:

Zona glomerulosa, which produces predominately mineralocorticoid

Zona fasciculata, which produces predominately glucocorticoid

Zona reticularis, which produces predominately androgens

For convenience, think of the zona glomerulosa as the first endocrine organ and the zonae fasciculata and reticularis collectively as a second separate endocrine organ, as distinguished by distinct control systems.

Aldosterone (mineralocorticoid) synthesis and secretion is regulated via the renin-angiotensin system, which is responsive to the electrolyte balance state and plasma volume. Aldosterone secretion is also directly stimulated by high serum potassium concentrations. In contrast, cortisol synthesis and secretion is regulated by adrenocorticotropic hormone (ACTH), which stimulates the enzyme P-450scc (20, 22 desmolase) with subsequent increased production of all adrenal steroids in both the zona fasciculata and zona reticularis.

Congenital adrenal hyperplasia (CAH) is a family of autosomal recessive disorders of adrenal steroid biosynthesis in which one of the enzymes necessary for cortisol production has deficient activity. Decreased serum cortisol levels stimulate ACTH release via negative feedback. The adrenal glands undergo hypertrophy, apparently due to ACTH-stimulated production of insulinlike growth factor-2 (IGF-2). Increased ACTH secretion also results in overproduction of both the adrenal steroids preceding the missing enzyme and those that do not require the missing enzyme (ie, build-up of compounds both before the block and “sideways” from the block). See following image. Treatment with exogenous glucocorticoid decreases ACTH secretion and subsequent suppression of overproduced steroids.

Cytochrome P450c17, an enzyme complex present in Leydig cells, ovarian follicles, and the adrenal zonae fasciculata and reticularis, catalyzes both 17-hydroxylase and 17,20 lyase activity. As might be expected from its location, P450c17 defects affect both adrenal and gonadal steroid production. P450c17 is the product of the cytochrome P45017 alpha gene (CYP17A1), and specific mutations of this gene cause varying degrees of partial-to-severe isolated 17-hydroxylase deficiency, isolated 17,20 lyase deficiency, or combined deficiencies. [1, 2, 3, 4, 5]

More than 80 different genetic mutations of the CYP17A1 gene have been described worldwide in patients wtih 17-hydroxylase deficiency, [6] with different mutations occurring more commonly in different populations. [5, 6, 7, 8, 9, 10]  For example, among the Chinese Han, 2 CYP17A1 mutations, D487-S488-F489 deletion and TAC329AA, account for the majority of 17-hydroxylase deficiency cases. [6] Different CYP17A1 mutations have been found in other Chinese cases, including novel nonsense mutations R449C and L209P. [7] By contrast, in a Brazilian cohort of 19 families with 17-hydroxylase deficiency, [8] 7 different CYP17 mutations were found among 24 subjects. However, 2 mutations accounted for most cases: W406R (50%) and R362C (32%). In these families, phenotypic features varied among the subjects and did not correlate with the CYP17 genotype.

A rare cause of 17-hydroxylase deficiency syndrome, first reported in 2004, is autosomal recessive P450 oxidoreductase (POR) deficiency. POR is an obligate electron donor for all microsomal P450 enzymes, including P450c17 (17α-hydroxylase/17,20 lyase), P450c21 (21-hydroxylase) and P450 aro (aromatase). POR deficiency can affect multiple steroidogenic pathways and have variable presentations depending on relative degrees of impaired enzyme activity. Drug metabolism may also be affected in these patients as many drugs are metabolized by hepatic P450s. [11, 12, 13, 14]

C-17α-hydroxylase is necessary to convert pregnenolone to 17-hydroxypregnenolone (17-OH Preg) and progesterone to 17-hydroxyprogesterone (17-OH Prog); see first image below. Thus, absence of this enzyme impairs all sex steroid and cortisol production (see second image below). Low levels of cortisol result in increased ACTH stimulation of steroids prior to the 17-hydroxylase step, resulting in increased accumulation and secretion of 17-deoxysteroids by the zona fasciculata, including pregnenolone, progesterone, deoxycorticosterone (DOC), and corticosterone (compound B).

Hypogonadism occurs as a result of deficient sex steroid production. DOC mineralocorticoid activity causes sodium retention, plasma volume expansion, hypertension, hypokalemia, and decreased renin and aldosterone levels in most untreated patients with 17-hydroxylase deficiency.

Approximately 80-90% of individuals with CAH have 21-hydroxylase deficiency. The incidence of classic 21-hydroxylase deficiency varies from 1 in 5,000-15,000 live births in white populations to 1 in 300-700 in the Alaskan Yupik population. Milder (nonclassic) 21-hydroxylase deficiency is estimated to occur in 1 in 1,000 individuals. [15] The second most common type of CAH, 11-β -hydroxylase deficiency, has an incidence of about 1 in 100,000 individuals (see C-11 Hydroxylase Deficiency). 17-Hydroxylase deficiency is even rarer.

17-Hydroxylase deficiency occurs worldwide. However, as of 2010, only about 130 individuals with severe, confirmed 17-hydroxylase deficiency had been documented, [16] and most of these reported cases were either isolated or occurred in small clusters. Examples include Turkey, where the reported incidence was 1 in 273 patients with CAH over a 25-year period [17] ; Brazil, where 16 cases were reported over a 10-year period [8] ; and Puerto Rico, where 1 case was reported. [18] . New cases of 17-hydroxylase deficiency continue to be reported, [9, 10] but the worldwide incidence remains low, especially compared with other forms of CAH.

A diagnosis of 17-hydroxylase deficiency may be suspected in infancy or childhood when hypokalemia and hypertension are found in association with either ambiguous genitalia or in an apparent female patient with a hernia or inguinal mass. However, many patients may go undiagnosed until adolescence or young adulthood. Karyotypic 46,XY patients may be undiagnosed until puberty, having been raised as females, and present to an endocrinologist or nephrologist for evaluation due to lack of secondary sexual characteristics and varying degrees of hypertension and hypokalemia. Similarly, 46,XX patients are usually diagnosed upon presentation of delayed puberty or lack of menses, along with hypertension and hypokalemia. [16]

Difficulties may arise when this relatively rare diagnosis is not considered, as in the examples described below.

Most patients with 17-hydroxylase (17-OH) deficiency syndrome have some degree of hypertension. Appropriate treatment primarily consists of exogenous glucocorticoid therapy; only more severely affected individuals require antihypertension medications. Failure to reach the proper diagnosis in such a patient may lead to inappropriate or incomplete treatment of the hypertension.

Because patients may appear normal at birth and throughout childhood, female patients may not be diagnosed until they present at a later age with delayed puberty or amenorrhea. Appropriate treatment consists of exogenous sex steroid replacement plus glucocorticoid therapy. Failure to distinguish between 17-hydroxylase deficiency syndrome and other, more common causes of delayed puberty may lead to incomplete treatment.

Because patients with P450 oxidoreductase (POR) deficiency can present with multiple clinical manifestations and have defects in various steroidogenic enzymes, they may be mistakenly diagnosed. [19] Differentiating 17-hydroxylase deficiency syndrome from POR deficiency is important because patients with POR deficiency have the additional potential for adrenal insufficiency. [11, 12] POR should be suspected in patients with adrenal insufficiency and genital anomalies who have associated skeletal malformations.

Although extensive literature and experience regarding treatment of pediatric patients is available, little has been published regarding treatment of adults with congenital adrenal hormone deficiencies. Certainly, no consensus or published guidelines are available regarding types, dosages, or timing of steroid replacement in adult patients. [20, 21]

One survey in the United Kingdom demonstrated that the most widely used glucocorticoid in adult patients was hydrocortisone, followed by dexamethasone and prednisolone. Sixty percent of physicians surveyed used larger doses of glucocorticoids at night (reverse circadian pattern) to achieve adrenocorticotropic hormone (ACTH) suppression, and only 16% of treating physicians used body weight or surface area to determine dosage.

Adult patients must be continuously and carefully treated, using body size or weight-related dosages (in a manner analogous to pediatric treatment) to avoid extremes of overtreatment and undertreatment.

Auchus RJ, Gupta MK. Towards a unifying mechanism for CYP17 mutations that cause isolated 17,20-lyasedeficiency. Endocr Res. 2002 Nov. 28(4):443-7. [Medline].

Rosa S, Duff C, Meyer M, et al. P450c17 deficiency: clinical and molecular characterization of six patients. J Clin Endocrinol Metab. 2007 Mar. 92(3):1000-7. [Medline].

Tian Q, Zhang Y, Lu Z. Partial 17alpha-hydroxylase/17,20-lyase deficiency-clinical report of five Chinese 46,XX cases. Gynecol Endocrinol. 2008 Jul. 24(7):362-7. [Medline].

Bhangoo A, Aisenberg J, Chartoffe A, et al. Novel mutation in cytochrome P450c17 causes complete combined 17alpha-hydroxylase/17,20-lyase deficiency. J Pediatr Endocrinol Metab. 2008 Feb. 21(2):185-90. [Medline].

Krone N, Arlt W. Genetics of congenital adrenal hyperplasia. Best Pract Res Clin Endocrinol Metab. 2009 Apr. 23(2):181-92. [Medline].

Bao X, Ding H, Xu Y, Cui G, He Y, Yu X, et al. Prevalence of common mutations in the CYP17A1 gene in Chinese Han population. Clin Chim Acta. 2011 Jun 11. 412(13-14):1240-3. [Medline].

Tian Q, Yao F, Zhang Y, Tseng H, Lang J. Molecular study of five Chinese patients with 46XX partial 17a-hydroxylase/17,20-lyase deficiency. Gynecol Endocrinol. 2012 Mar. 28(3):234-8. [Medline].

Costa-Santos M, Kater CE, Auchus RJ, Brazilian Congenital Adrenal Hyperplasia Multicenter Study Group. Two prevalent CYP17 mutations and genotype-phenotype correlations in 24 Brazilian patients with 17-hydroxylase deficiency. J Clin Endocrinol Metab. 2004 Jan. 89(1):49-60. [Medline]. [Full Text].

Kim YM, Kang M, Choi JH, Lee BH, Kim GH, Ohn JH, et al. A review of the literature on common CYP17A1 mutations in adults with 17-hydroxylase/17,20-lyase deficiency, a case series of such mutations among Koreans and functional characteristics of a novel mutation. Metabolism. 2014 Jan. 63 (1):42-9. [Medline].

Zhang M, Sun S, Liu Y, Zhang H, Jiao Y, Wang W, et al. New, recurrent, and prevalent mutations: Clinical and molecular characterization of 26 Chinese patients with 17alpha-hydroxylase/17,20-lyase deficiency. J Steroid Biochem Mol Biol. 2015 Jun. 150:11-6. [Medline].

Fluck CE, Pandey AV, Huang N, et al. P450 oxidoreductase deficiency – a new form of congenital adrenal hyperplasia. Endocr Dev. 2008. 13:67-81. [Medline].

Scott RR, Miller WL. Genetic and clinical features of p450 oxidoreductase deficiency. Horm Res. 2008. 69(5):266-75. [Medline].

Arlt W. P450 oxidoreductase deficiency and Antley-Bixler syndrome. Rev Endocr Metab Disord. 2007 Dec. 8(4):301-7. [Medline].

Fukami M, Horikawa R, Nagai T, Tanaka T, Naiki Y, Sato N, et al. Cytochrome P450 oxidoreductase gene mutations and Antley-Bixler syndrome with abnormal genitalia and/or impaired steroidogenesis: molecular and clinical studies in 10 patients. J Clin Endocrinol Metab. 2005 Jan. 90(1):414-26. [Medline].

Auchus RJ. The classic and nonclassic concenital adrenal hyperplasias. Endocr Pract. 2015 Apr. 21 (4):383-9. [Medline].

Aydin Z, Ozturk S, Gursu M, Uzun S, Karadag S, Kazancioglu R. Male pseudohermaphroditism as a cause of secondary hypertension: a case report. Endocrine. 2010 Aug. 38(1):100-3. [Medline].

Kandemir N, Yordam N. Congenital adrenal hyperplasia in Turkey: a review of 273 patients. Acta Paediatr. 1997 Jan. 86(1):22-5. [Medline].

Rosado A, Alegre M, Colon G. [Male pseudohermaphroditism caused by enzymatic deficiency of 17-alpha- hydroxylase. 1st case reported in Puerto Rico]. Bol Asoc Med P R. 1997 Oct-Dec. 89(10-12):197-9. [Medline].

Hershkovitz E, Parvari R, Wudy SA, et al. Homozygous Mutation G539R in the Gene for P450 Oxidoreductase in a Family Previously Diagnosed as Having 17,20-Lyase Deficiency. J Clin Endocrinol Metab. 2008 Sep. 93(9):3584-8. [Medline].

Monig H, Sippell W. Congenital adrenal hyperplasia in adulthood: do men need to continue treatment?. Horm Res. 2005. 64 Suppl 2:71-3. [Medline].

Ross RJ, Rostami-Hodjegan A. Timing and type of glucocorticoid replacement in adult congenital adrenal hyperplasia. Horm Res. 2005. 64 Suppl 2:67-70. [Medline].

Philip J, Anjali N, Thomas S, et al. 17-Alpha hydroxylase deficiency: an unusual cause of secondary amenorrhoea. Aust N Z J Obstet Gynaecol. 2004 Oct. 44(5):477-8. [Medline].

Imai T, Yanase T, Waterman MR, et al. Canadian Mennonites and individuals residing in the Friesland region of The Netherlands share the same molecular basis of 17 alpha-hydroxylase deficiency. Hum Genet. 1992 Apr. 89(1):95-6. [Medline].

Reisch N, Idkowiak J, Hughes BA, Ivison HE, Abdul-Rahman OA, Hendon LG, et al. Prenatal diagnosis of congenital adrenal hyperplasia caused by P450 oxidoreductase deficiency. J Clin Endocrinol Metab. 2013 Mar. 98(3):E528-36. [Medline]. [Full Text].

Marsh CA, Auchus RJ. Fertility in patients with genetic deficiencies of cytochrome P450c17 (CYP17A1): combined 17-hydroxylase/17,20-lyase deficiency and isolated 17,20-lyase deficiency. Fertil Steril. 2014 Feb. 101 (2):317-22. [Medline].

Achermann JC, Hughes LA. Disorders of Sex Development. Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa: Saunders; 2011. 868-935.

Stewart PM, Krone NP. The Adrenal Cortex. Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa: Saunders; 2011. 479-545.

J Paul Frindik, MD, FACE Associate Professor, Department of Pediatrics, University of Arkansas for Medical Sciences College of Medicine

J Paul Frindik, MD, FACE is a member of the following medical societies: American Association of Clinical Endocrinologists

Disclosure: Nothing to disclose.

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Barry B Bercu, MD Professor, Departments of Pediatrics, Molecular Pharmacology and Physiology, University of South Florida College of Medicine, All Children’s Hospital

Barry B Bercu, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Clinical Endocrinologists, American Medical Association, American Pediatric Society, Association of Clinical Scientists, Endocrine Society, Florida Medical Association, Pediatric Endocrine Society, Society for Pediatric Research, Southern Society for Pediatric Research, Society for the Study of Reproduction, American Federation for Clinical Research, Pituitary Society

Disclosure: Nothing to disclose.

Stephen Kemp, MD, PhD Former Professor, Department of Pediatrics, Section of Pediatric Endocrinology, University of Arkansas for Medical Sciences College of Medicine, Arkansas Children’s Hospital

Stephen Kemp, MD, PhD is a member of the following medical societies: American Academy of Pediatrics, American Association of Clinical Endocrinologists, American Pediatric Society, Endocrine Society, Phi Beta Kappa, Southern Medical Association, Southern Society for Pediatric Research

Disclosure: Nothing to disclose.

Erawati V Bawle, MD, FAAP, FACMG Retired Professor, Department of Pediatrics, Wayne State University School of Medicine

Erawati V Bawle, MD, FAAP, FACMG is a member of the following medical societies: American College of Medical Genetics and Genomics, American Society of Human Genetics

Disclosure: Nothing to disclose.

17-Hydroxylase Deficiency Syndrome

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