Genetics of Congenital Adrenal Hyperplasia

Genetics of Congenital Adrenal Hyperplasia
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Congenital adrenal hyperplasia isn’t a single disorder, but a group of inherited disorders affecting the adrenal gland. This genetic disorder can affect both girls and boys and approximately one in 10,000 to 18,000 children are born with this disorder. Understanding the genetics of congenital adrenal hyperplasia is important because it can help determine many aspects of this disease, such as how it occurs and how to treat it.

Genetic Cause

The most common cause of congenital adrenal hyperplasiais an enzyme 21-hydroxylase deficiency. This enzymes gene lies on chromosome six. This gene has two copies because hundreds of thousands of years ago a duplication occurred. The active copy of this gene is called CYP21 and the inactive copy of this gene is called CYP21P. Various levels of enzyme result from the various 21-hydroxylase gene mutations. There is a spectrum of effects as a consequence.

Those who have this condition will not have the enzyme that the adrenal gland needs to produce the hormones aldosterone and cortisol. With the absence of these hormones, more androgen will be produced by the body. Androgen is a type of male sex hormone and when too much of this hormone is produced, it results in male characteristics to appear inappropriately or early.

Symptoms of Congenital Adrenal Hyperplasia

Girls will most often have normal female reproductive organs. However, they can experience abnormal menstrual periods, ambiguous genitalia that often appears more male than female, deep voice, failure to menstruate, early appearance of armpit hair and pubic hair, and facial hair and excessive hair growth.

Boys will seem fine at birth and won’t have any obvious symptoms. However, boys may seem to enter puberty much earlier than normal, such as at two to three years old. They may also experience deep voice, well-developed muscles, early appearance of armpit hair and pubic hair, small testes, developing male characteristics early, and enlarged penis.

Some forms of this genetic disorder are more severe than others and cause adrenal crisis in newborns due to salt loss. When newborns have the more severe forms, they develop symptoms that are severe shortly after they are born. These include cardiac arrhythmias, electrolyte changes, dehydration, and vomiting.

Treating Congenital Hyperplasia

The main goal of treatment is to normalize hormone levels. This is done by having the patient take a form of cortisol, such as fludrocortisone, dexamethasone, or hydrocortisone, every day. During stressful times, such as surgery or severe illness, patients may need to take additional doses of their medication.

By checking the chromosomes, also referred to as karyotyping, health care providers can identify the baby’s gender even if they have ambiguous genitalia. Girls who have genitalia that resembles that of a male will most often undergo surgery to correct the abnormal appearance at one to three months old.


Medline Plus. (2010). Congenital Adrenal Hyperplasia. Retrieved on March 30, 2010 from Medline Plus:

Wrong Diagnosis. (2010). Inheritance and Genetics of Congenital Adrenal Hyperplasia. Retrieved on March 30, 2010 from Wrong Diagnosis:

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Damaged DNA: Square87 – Wikimedia Commons