Congenital Adrenal Hyperplasia 

  • Author: Thomas A Wilson, MD; Chief Editor: Stephen Kemp, MD, PhD   more...
 
Updated: Sep 17, 2010
 

Background

The term congenital adrenal hyperplasia (CAH) encompasses a group of autosomal recessive disorders, each of which involves a deficiency of an enzyme involved in the synthesis of cortisol,[1] aldosterone, or both.

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Pathophysiology

The clinical manifestations of each form of congenital adrenal hyperplasia are related to the degree of cortisol deficiency and/or the degree of aldosterone deficiency. In some cases, these manifestations reflect the accumulation of precursor adrenocortical hormones. When present in supraphysiologic concentrations, these precursors cause abnormalities such as virilization or hypertension.

The phenotype depends on the degree or type of gene deletion or mutation and the resultant deficiency of the steroidogenic enzyme. The enzymes and corresponding genes are displayed in the image below.

Enzymes and genes involved in adrenal steroidogeneEnzymes and genes involved in adrenal steroidogenesis.

Two copies of an abnormal gene are required for disease to occur, and not all mutations and partial deletions result in disease. The phenotype can vary from clinically inapparent disease (occult or cryptic adrenal hyperplasia) to a mild form of disease that is expressed in adolescence or adulthood (nonclassic adrenal hyperplasia) to severe disease that results in adrenal insufficiency in infancy with or without virilization and salt wasting (classic adrenal hyperplasia). The most common form of adrenal hyperplasia (due to a deficiency of 21-hydroxylase activity) is clinically divided into 3 phenotypes: salt wasting, simple virilizing, and nonclassic.

CYP21A is the gene that codes for 21-hydroxylase, CYP11B1 codes for 11-beta-hydroxylase, and CYP17 codes for 17-alpha-hydroxylase. Many of the enzymes involved in cortisol and aldosterone syntheses are cytochrome P450 (CYP) proteins.

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Epidemiology

Frequency

United States

The most common form of congenital adrenal hyperplasia is due to mutations or deletions of CYP21A, resulting in 21-hydroxylase deficiency. This deficiency accounts for more than 90% of adrenal hyperplasia cases. Mutations or partial deletions that affect CYP21A are common, with estimated frequencies as high as 1 in 3 individuals in selected populations (eg, Ashkenazi Jews) to 1 in 7 individuals in New York City. The estimated prevalence is 1 case per 60 individuals in the general population.

Classic adrenal hyperplasia has an overall prevalence of 1 case per 16,000 population; however, in selected populations (eg, the Yupik of Alaska), the prevalence is as high as 1 case in 400 population. Congenital adrenal hyperplasia caused by 11-beta-hydroxylase deficiency accounts for 5-8% of all congenital adrenal hyperplasia cases.

International

Congenital adrenal hyperplasia caused by 21-hydroxylase deficiency is found in all populations. 11-beta-hydroxylase deficiency is more common in persons of Moroccan or Iranian-Jewish descent.

Mortality/Morbidity

The morbidity of the various forms of adrenal hyperplasia is best understood in the context of the steroidogenic pathway, shown below, used by the adrenal glands and gonads.

Steroidogenic pathway for cortisol, aldosterone, aSteroidogenic pathway for cortisol, aldosterone, and sex steroid synthesis. A mutation or deletion of any of the genes that code for enzymes involved in cortisol or aldosterone synthesis results in congenital adrenal hyperplasia. The particular phenotype that results depends on the sex of the individual, the location of the block in synthesis, and the severity of the genetic deletion or mutation.

The clinical phenotype can be understood by analyzing the location of the enzyme deficiency, the accumulation of precursor hormones, and the physiologic action of those hormones (see History).

Severe forms of congenital adrenal hyperplasia are potentially fatal if unrecognized and untreated because of the severe cortisol and aldosterone deficiencies that result in salt wasting, hyponatremia, hyperkalemia, dehydration, and hypotension.

Race

Congenital adrenal hyperplasia occurs among people of all races. Congenital adrenal hyperplasia secondary to CYP21A1 mutations and deletions is particularly common among the Yupik Eskimos.

Sex

Because all forms of congenital adrenal hyperplasia are autosomal recessive disorders, both sexes are affected with equal frequency. However, because accumulated precursor hormones or associated impaired testosterone synthesis impacts sexual differentiation, the phenotypic consequences of mutations or deletions of a particular gene differ between the sexes.

Age

Classic congenital adrenal hyperplasia is generally recognized at birth or in early childhood because of ambiguous genitalia, salt wasting, or early virilization. Nonclassic adrenal hyperplasia is generally recognized at or after puberty because of oligomenorrhea or virilizing signs in females.

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Contributor Information and Disclosures
Author

Thomas A Wilson, MD  Professor of Clinical Pediatrics, Director of Pediatric Endocrinology, Department of Pediatrics, The School of Medicine at Stony Brook University Medical Center

Thomas A Wilson, MD is a member of the following medical societies: Endocrine Society, Lawson-Wilkins Pediatric Endocrine Society, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Specialty Editor Board

Arlan L Rosenbloom, MD  Adjunct Distinguished Service Professor Emeritus of Pediatrics, University of Florida; Fellow of the American Academy of Pediatrics; Fellow of the American College of Epidemiology

Arlan L Rosenbloom, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Epidemiology, American Pediatric Society, Endocrine Society, Florida Pediatric Society, Lawson-Wilkins Pediatric Endocrine Society, and Society for Pediatric Research

Disclosure: Nothing to disclose.

Mary L Windle, PharmD  Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Pharmacy Editor, eMedicine

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 Federation for Clinical Research, American Medical Association, American Pediatric Society, Association of Clinical Scientists, Endocrine Society, Florida Medical Association, Lawson-Wilkins Pediatric Endocrine Society, Pituitary Society, Society for Pediatric Research, Society for the Study of Reproduction, and Southern Society for Pediatric Research

Disclosure: Nothing to disclose.

Merrily P M Poth, MD  Professor, Department of Pediatrics and Neuroscience, Uniformed Services University of the Health Sciences

Merrily P M Poth, MD is a member of the following medical societies: American Academy of Pediatrics, Endocrine Society, and Lawson-Wilkins Pediatric Endocrine Society

Disclosure: Nothing to disclose.

Chief Editor

Stephen Kemp, MD, PhD  Professor, Department of Pediatrics, Section of Pediatric Endocrinology, University of Arkansas and 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, and Southern Society for Pediatric Research

Disclosure: Genentech, Inc. Honoraria Speaking and teaching; Pfizer, Inc. Honoraria Consulting

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Enzymes and genes involved in adrenal steroidogenesis.
Steroidogenic pathway for cortisol, aldosterone, and sex steroid synthesis. A mutation or deletion of any of the genes that code for enzymes involved in cortisol or aldosterone synthesis results in congenital adrenal hyperplasia. The particular phenotype that results depends on the sex of the individual, the location of the block in synthesis, and the severity of the genetic deletion or mutation.
A female patient with the 46,XX karyotype with mild virilization due to congenital virilizing adrenal hyperplasia secondary to 21-hydroxylase deficiency. Despite the mild clitoromegaly, this patient has fusion of the labial-scrotal folds and salt wasting.
Severe virilization in a female patient with the 46,XX karyotype with congenital adrenal hyperplasia secondary to 21-hydroxylase deficiency. This patient also has salt wasting.
Short stature in a male patient with congenital adrenal hyperplasia secondary to 21-hydroxylase deficiency. His compliance with medical therapy was poor, and early growth and skeletal maturation was advanced, resulting in early puberty and completion of growth. This 12-year-old boy has reached final adult height, which is well below that of his mother.
 
 
 
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