Located on top of each kidney, the adrenal glands make hormones that help regulate metabolism, the immune system, blood pressure and other important functions. Although small, these glands control much of what happens in the body.
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 required for growth and development in both males and females
In people who have CAH, a gene change (mutation) results in a lack of one of the enzymes needed to make these hormones.
The two major types of congenital adrenal hyperplasia are:
- Classic CAH. This rarer, more-severe form is usually detected at birth or in early infancy.
- Nonclassic CAH. This form is milder and more common. It may not be identified until childhood or early adulthood.
Although there is no cure, with proper treatment, most people who have CAH. can lead full lives.
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Signs and symptoms of CAH vary, depending on which gene is affected and the level of enzyme deficiency. The imbalance of hormones the body needs to function may mean too little cortisol, too little aldosterone, excess androgens or a combination of these imbalances.
Signs and symptoms of classic CAH may include:
- Insufficient cortisol. Classic CAH causes the body to produce an insufficient amount of cortisol. This can cause problems maintaining normal blood pressure, blood sugar and energy levels, and cause problems during physical stress such as illness.
- Adrenal crisis. People with classic CAH 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.
Atypical genitalia. Female infants may have atypical genitalia appearance, such as an enlarged clitoris that may resemble a penis, and a partially closed labia resembling a scrotum. The urinary opening (urethra) and the vagina may be only one opening instead of two separate openings. The uterus, fallopian tubes and ovaries usually develop typically.
Male infants usually have typical-appearing genitals.
Excess androgen. An excess of the male sex hormone androgen can result in short height and early puberty for both males and females. Pubic hair and other signs of puberty may appear at a very early age. Severe acne also may occur.
Excess androgen hormones in females may result in facial hair, excessive body hair and a deepening voice.
- Altered growth. Rapid growth may occur during childhood with an advanced bone age. Final height may be shorter than average.
- Fertility issues. These can include irregular menstrual periods, or not having any at all, and having infertility problems in females. Fertility issues can sometimes occur in males.
Often there are no symptoms of nonclassic CAH when a baby is born. Some people with nonclassic CAH never have symptoms. 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.
Females who have nonclassic CAH may have typical-appearing genitals at birth. Later in life, they may experience:
- Irregular menstrual periods, or not having any at all, and problems getting pregnant
- Masculine characteristics such as facial hair, excessive body hair and a deepening voice
In both females and males, signs of nonclassic CAH may also include:
- Early appearance of pubic hair and other signs of early puberty
- Severe acne
- Rapid growth during childhood with an advanced bone age and shorter than expected final height
When to see a doctor
Classic CAH is usually detected at birth through routine newborn screening or when babies have atypical 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 health care provider.
If you are pregnant and may be at risk of CAH because of your own medical history or your ethnicity, ask your health care provider about genetic counseling.
Autosomal recessive inheritance pattern
In an autosomal recessive disorder, two changed genes are inherited, one from each parent. The parents' health is rarely affected because they have only one changed gene. Two carriers have a 25% chance of having an unaffected child with two unaffected genes. They have a 50% chance of having an unaffected child who also is a carrier. They have a 25% chance of having an affected child with two changed genes.
The most common cause of CAH is the lack of the enzyme known as 21-hydroxylase. CAH may sometimes be called 21-hydroxylase deficiency. This enzyme is required by the body to make proper amounts of hormones. There are other much rarer enzyme deficiencies that also cause CAH.
CAH is a genetic disorder, which means it's inherited from parents and is present at birth. Children who have the condition have two parents who either have CAH themselves or who are both carriers of the genetic change 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 change for the disorder
- Being of Ashkenazi Jewish, Latino, Mediterranean, Yugoslav or Yup'ik ancestry
People who have classic CAH are at risk of adrenal crisis. This is a life-threatening medical emergency that requires immediate treatment. Adrenal crisis can occur within the first few days after birth. It can also be triggered at any age by infectious illness or physical stress such as surgery.
Very low levels of cortisol in the blood can cause diarrhea, vomiting, dehydration, low blood sugar levels, seizures and shock. 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.
People who have either classic or nonclassic CAH may experience fertility problems.
There is no known way to prevent CAH. If you're thinking of starting a family and you're at risk of having a child with CAH, your health care provider may recommend that you see a genetic counselor.