What Is Congenital Adrenal Hyperplasia?

The body's adrenal glands are two cone-shaped organs that sit on top of the kidneys. They make hormones that affect metabolism, the immune system, blood pressure, stress responses, and other important functions.

Hormones made by the adrenal glands include:

• aldosterone — which keeps the kidneys from losing too much salt in urine (pee)
• cortisol — a stress response hormone that's also needed for control of blood pressure, blood sugar levels, and immune system activity
• androgens — hormones involved in sexual development

In congenital adrenal hyperplasia (CAH), a mutation (genetic change) causes the adrenal glands to make too little cortisol. In the most common type of CAH, called 21-hydroxylase deficiency, the adrenal glands also might not make aldosterone. As the adrenal glands work harder to try to make more cortisol, they produce too much testosterone and other androgen hormones.

What Are the Signs & Symptoms of Congenital Adrenal Hyperplasia?

Congenital adrenal hyperplasia symptoms will depend on a child's age, sex, and which hormones the adrenal glands make too little or too much of.

Some types of CAH can cause a baby with female (XX) chromosomes to develop ambiguous (in-between) genitalia or genitals that appear male. Other types can cause a baby with male (XY) chromosomes to develop genitals that appear female.

Newborns with untreated severe CAH usually have some of these symptoms within the first few weeks of life:

• vomiting
• dehydration
• failure to gain weight

Babies with milder forms of CAH may have no symptoms. Older kids and teens with mild or moderate CAH may:

• grow taller than average in early childhood and stop growing sooner than peers (which may lead to a shorter than average adult height if they are not treated)
• have a larger than average clitoris (girls)
• not have these changes expected with puberty, or have them earlier or later than peers:
  • girls — pubic and armpit hair, breast development, menstruation (periods)
  • boys — pubic, armpit, facial, and chest hair; voice change; increase in penis size

Very mild CAH might be undiagnosed until fertility problems arise in adulthood.

What Causes Congenital Adrenal Hyperplasia?

Everyone has two copies of almost every gene. Children with mutations in both copies of a CAH-related gene can have CAH. These mutations cause low levels of enzymes needed to make adrenal hormones. In the most common forms of CAH, this leads to low levels of cortisol and sometimes also aldosterone, and high levels of androgens.

Who Gets Congenital Adrenal Hyperplasia?

People with a mutation in only one of the CAH-related genes do not have symptoms of CAH. But they're called CAH carriers because they can pass the CAH-causing gene to their children.

The genetic pattern through which CAH passes from parents to children is called autosomal recessive. This means that when two CAH carriers have a child, there is a 25% chance that the child will have CAH.

How Is Congenital Adrenal Hyperplasia Diagnosed?

A prenatal ultrasound scan may find CAH before a baby is born. But usually it's suspected at birth or soon after based on symptoms (such as abnormal-appearing genitals) or the results of a newborn screening blood test that's done on all newborns in the U.S.

A specialist in pediatric endocrinology usually checks the baby to see which adrenal enzyme is missing and directs treatment.

Tests that help confirm the diagnosis of CAH or guide treatment may include:

• blood tests to check levels of adrenal hormones
• blood chemistry to check sodium and high potassium levels in children with salt-losing types of CAH
• karyotype to determine chromosomal sex
• imaging tests (such as an ultrasound study) to get more information about genital anatomy
• X-rays to see how rapidly the bones mature

How Is Congenital Adrenal Hyperplasia Treated?

Children with CAH are treated by a care team. The team usually includes the child's primary care doctor, a pediatric endocrinologist , a urologist, and a geneticist.

A child with severe CAH needs lifelong hormone replacement and extra cortisol during times of illness, stress, or injury.

Treatment with hydrocortisone replaces the cortisol deficiency, and prevents low blood sugars and low blood pressure. It can help prevent the effects on growth and puberty that untreated CAH causes. Children with aldosterone deficiency may need treatment with fludrocortisone (a medicine that works like aldosterone) to maintain body salt balance. Some infants may also have to take salt supplements by mouth.

Surgery may be considered to correct the genitals' appearance and function.

With the recommended hormone treatment and close follow-up with a pediatric endocrinologist, children with CAH can grow and develop like other children. In adulthood, most will be able to have children of their own.

What Else Should I Know?

• Caregivers should learn when and how to give emergency treatment (such as for a serious illness or injury), including how to give an injection of hydrocortisone, if needed.
• Kids with CAH should wear a medical ID necklace or bracelet.
• Genetic testing can be done to identify CAH carriers and for prenatal diagnosis.