Congenital Adrenal Hyperplasia (CAH)
What is Congenital Adrenal Hyperplasia (CAH)?
Congenital Adrenal Hyperplasia (CAH) is a medical condition that has different types. The most common type—90% of cases of CAH—is called 21-hydroxylase deficiency. Parents most often find out that their baby has CAH from newborn screening. CAH occurs when the adrenal glands are unable to produce hormones normally, leading to a hormone imbalance. CAH can be life threatening if not properly treated. 
What these big words mean:
- Congenital means present at birth.
- Adrenal refers to the adrenal glands, located at the top of the kidneys.
- Hyperplasia is a medical word for an organ or tissue growing too large. In CAH, the adrenal glands grow bigger as they try to make up for the hormones they aren’t making enough of.
- 21-hydroxylase (21-OH) is the enzyme the adrenal glands need to help it make certain hormones. When there is not enough of it, the adrenal hormones get out of balance.
What causes CAH?
CAH is caused by not having enough of an enzyme (most commonly 21-hydroxylase) that the adrenal glands need to work right. The adrenal glands are part of the endocrine system. The adrenal glands make hormones, chemical “messengers” that the body needs to function well. In CAH, the adrenal glands make too little of certain hormones. These hormones are cortisol and aldosterone.
- Cortisol is a “stress hormone.” Our bodies need it when we are sick or injured. Cortisol is a hormone in the family of hormones called “glucocorticoids.”
- Aldosterone is the “salt-retaining hormone.” It helps our bodies hold on to salt to balance the fluids and electrolytes in our system. Aldosterone is a hormone in the family of hormones called “mineralocorticoids.”
When the adrenal glands make too little cortisol and aldosterone, it can endanger the child’s life. But by replacing hormones through medical treatment, a child will be able to develop normally and be healthy.
In 21-OH CAH, when the adrenal glands try to make cortisol and aldosterone, they instead make more of other hormones: androgens. Androgens are another group of hormones involved in CAH. Both males and females make androgens, but males make more. Having too much androgen affects how girls’ bodies develop, even before they are born.
- AboutKidsHealth offers a helpful, interactive explanation (with pictures and animation) of what happens with enzymes and adrenal hormones in CAH.
What are the different types of CAH?
- Classic forms of CAH (more severe):
- Salt-wasting CAH (SWCAH): The adrenal glands cannot make cortisol (stress hormone) or aldosterone (salt-retaining hormone) causing the fluid and electrolytes in the body to be out of balance. It can be life threatening if not treated properly. At the same time, the adrenal glands make too much androgen.
- Simple-virilizing CAH (SVCAH, also known as non salt-wasting CAH—NSWCAH): The adrenal glands make enough aldosterone, but not enough cortisol. They make too much androgen, but often less than in SWCAH.
- Non-classic CAH (NCAH) is also known as late-onset CAH. It is a milder form of CAH and is not life threatening. The adrenal glands produce normal or nearly normal amounts of cortisol and aldosterone. But they also make too much androgen. In late childhood or adulthood, signs of excess male hormone appear. The excess androgens can cause early puberty, and problems like the development of unwanted body and facial hair, severe acne, or menstrual problems. Hormone replacement can treat this type of CAH in both boys and girls. Some people with non-classic CAH may benefit from medical treatment for the symptoms of the condition, such as acne treatment. Find out more about non-classic CAH from the CARES Foundation.
How is CAH inherited?
Parents can be carriers of the gene that causes CAH without being affected themselves. If both parents are carriers of the gene that leads to CAH, they can pass it to their child. If both parents pass the gene to the child, the child will have CAH. There is a 25% chance that the child of two unaffected carriers will have CAH. This type of inheritance is called autosomal recessive. If you have a child with CAH or you have CAH in your family, it’s a good idea to seek genetic counseling that can help you and your relatives with family planning.
How common is it?
About one in 15,000 children is born with the classic form of CAH each year in the United States. CAH occurs equally in boys and girls. Non-classic or late-onset CAH is one of the more common genetic conditions. It may affect one to five percent of people in a given community, varying by the racial and ethnic makeup. It is more common in certain ethnic groups.
Image of the adrenal glands reproduced courtesy of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), NIH, DHHS; http://www.nichd.nih.gov.
Written and compiled by Kyla Boyse, RN and Talyah Sands. Reviewed by David E. Sandberg, Ph.D.
May 2011
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