Congenital adrenal hyperplasia (CAH) is a genetic disorder in which the two adrenal glands (located at the top of the kidneys) do not function properly.
CAH is caused by genetic defects in the proteins and enzymes involved in cortisol biosynthesis. The most common mutation is in the gene encoding the adrenal steroid 21-hydroxylase, which is an enzyme responsible for converting cholesterol to cortisol within the adrenal glands. Without this enzyme, the adrenal glands may produce too little cortisol and/or aldosterone and too much androgen.
Adrenal Insufficient & Steroid Dependent FormSigns and Symptoms of CAH
The symptoms that present and the age at which they become apparent depends on the degree of cortisol and/or aldosterone deficiency. Boys with severe CAH show symptoms soon after birth, when a baby develops heart rhythm abnormalities, dehydration and vomiting. The levels of minerals (electrolytes) in the body are also affected, particularly showing low salt levels (hyponatraemia) and low blood sugar levels (hypoglycaemia).
Females with severe CAH are born with virilised (male looking) genitalia, so confusion as to the sex of the baby may occur. This is referred to as atypical or ambiguous genitalia. They too have low levels of minerals, especially salt, so show similar symptoms to boys.
Children with mild CAH may not have the same mineral imbalances as more severely affected children. Later, other symptoms caused by the increase in androgen develop. Girls will have abnormal or absent periods, a deep voice, early puberty and facial hair. Boys will have an enlarged penis, small testicles, early puberty, acne and a deep voice.
Both girls and boys may appear tall for their age but usually end up being short as adults if the diagnosis is not made quickly and treatment commenced.
Diagnosis?
Most cases of CAH are diagnosed soon after birth or in early childhood, but less severe CAH may not become apparent until a child does not start puberty at the expected age. CAH can be diagnosed before birth now that the affected gene has been identified. If a baby is born with ambiguous genitalia, blood tests are usually used to determine genetic gender. Blood and urine tests are also used to work out the levels of minerals and hormones in the body, so that they can be replaced. X-rays to look at a child’s bone age may also be suggested. Genetic testing may be used to identify the specific type of CAH and the associated gene deficiency or mutation.
Treatment?
Children with CAH are usually cared for by a multidisciplinary team including endocrinologists (hormone specialists) and urologists (genitourinary system specialists). Initially, children with CAH will need to be stabilised with intravenous fluids to restore their electrolyte levels. Once stable, cortisol and/or aldosterone replacement therapy can start with repeated blood tests to monitor hormone levels so the most effective dose can be prescribed.
Children with CAH will need to take replacement cortisol and aldosterone every day for the rest of their lives. However, if a person with cortisol deficiency becomes unwell, they are unable to increase the production of cortisol in their system to help the body cope and this could be life threatening – further details are available in our Cortisol deficiency and steroid replacement therapy information sheet.
