Perched atop each of your kidneys, your adrenal glands produce hormones that help regulate your metabolism, immune system, blood pressure and other essential functions.
Congenital adrenal hyperplasia (CAH) refers to a group of genetic disorders that affect the adrenal glands, a pair of walnut-sized organs above the kidneys. The adrenal glands produce important hormones, including:
- Cortisol, which regulates the body's response to illness or stress
- Mineralocorticoids, such as aldosterone, which regulate sodium and potassium levels
- Androgens, such as testosterone, which are male sex hormones
In people who have CAH, a genetic problem results in a lack of one of the enzymes needed to make these hormones.
Although there is no cure, with proper treatment, most people who have congenital adrenal hyperplasia can lead normal lives.
There are two major types of congenital adrenal hyperplasia:
- Classic CAH. This form is rarer and is usually detected in infancy. Approximately two-thirds of people who have classic CAH have what's known as the salt-losing form, while one-third have what's referred to as the simple-virilizing form.
- Nonclassic CAH. This form is milder and more common, and may not become evident until childhood or early adulthood.
Signs and symptoms of CAH vary, depending on which gene is defective and the level of enzyme deficiency.
Female infants who have classic CAH may have a condition known as ambiguous genitalia, in which the clitoris is enlarged or the genitals look more like those of a male child. Male infants who have classic CAH have normal appearing genitals. Both male and female infants can be seriously affected by a lack of cortisol, aldosterone or both. This is known as an adrenal crisis, and it can be life-threatening.
The salt-losing form and simple-virilizing form of classic CAH cause children's bodies to produce an insufficient amount of cortisol. These children can have problems maintaining normal blood pressure, normal blood sugar and energy levels, and are more vulnerable to stress. An excess of the male sex hormones can result in short height and early puberty for both boys and girls.
Signs and symptoms of classic CAH in children and adults include:
- Appearance of pubic hair at a very early age
- Rapid growth during childhood, but shorter than average final height
Often there are no symptoms of nonclassic CAH when a baby is born. The condition is not identified on routine infant blood screening and usually becomes evident in late childhood or early adulthood. Cortisol may be the only hormone that's deficient.
Teenage and adult females who have nonclassic CAH may have normal appearing genitals at birth, but later in life, they may experience:
- Irregular or absent menstrual periods
- Masculine characteristics such as facial hair, excessive body hair and a deepening voice
- Severe acne
In both females and males, signs of nonclassic CAH may also include:
- Early appearance of pubic hair
- Rapid growth during childhood, an advanced bone age and shorter predicted final height
When to see a doctor
Classic CAH is usually detected at birth through required newborn screening or when female babies have ambiguous genitalia. CAH may also be identified when male or female babies show signs of severe illness due to low levels of cortisol, aldosterone or both.
In children who have nonclassic CAH, signs and symptoms of early puberty may appear. If you have concerns about your child's growth or development, make an appointment with your child's doctor.
If you are pregnant and may be at risk of CAH because of your own medical history or your ethnicity, ask your doctor about genetic counseling.
Autosomal recessive inheritance pattern
To have an autosomal recessive disorder, you inherit two abnormal genes, one from each parent. A carrier has one abnormal gene (recessive gene) and one normal gene (dominant gene). Carrier health is not affected. Two carriers have a 25% chance of having an unaffected child with two normal genes (left), a 50% chance of having an unaffected child who also is a carrier (middle), and a 25% chance of having an affected child with two recessive genes (right).
The most common cause of CAH is the lack of the enzyme known as 21-hydroxylase. CAH may sometimes be called 21-hydroxylase deficiency. There are other much rarer enzyme deficiencies that also cause CAH.
Children who have the condition have two parents who either have CAH themselves or who are both carriers of the genetic mutation that causes the condition. This is known as the autosomal recessive inheritance pattern.
Factors that increase the risk of having CAH include:
- Parents who both have CAH or are both carriers of the genetic defect for the disorder
- Certain ethnic heritages, such as Ashkenazi Jew, but also Hispanic, Italian, Yugoslav and Yupik Inuit
People who have classic CAH are at risk of adrenal crisis because they have very low levels of cortisol in the blood. This can cause diarrhea, vomiting, dehydration, low blood sugar levels and shock. Adrenal crisis is a life-threatening medical emergency that requires immediate treatment. Aldosterone also may be low, which leads to dehydration and low sodium and high potassium levels. The nonclassic form of CAH doesn't cause adrenal crisis.
Males and females who have either classic or nonclassic CAH may also experience fertility problems.
There is no known way to prevent congenital adrenal hyperplasia. If you're thinking of starting a family and you're at risk of having a child with CAH, your doctor may recommend that you see a genetic counselor.