Congenital Adrenal Hyperplasia

Congenital adrenal hyperplasia (CAH) is a group of inherited conditions that affect how the adrenal glands make hormones. Most cases involve a shortage of the enzyme 21-hydroxylase, which can reduce cortisol production and sometimes aldosterone production. Classic forms may be detected in newborns or infancy, while milder, nonclassic forms may not appear until childhood, adolescence, or adulthood. The resulting hormone imbalance can affect salt balance, growth, puberty, and sex-related traits.

Symptoms in newborns and infants

Later symptoms of milder or nonclassic CAH

Congenital adrenal hyperplasia is usually caused by disease-causing variants in the CYP21A2 gene, which provides instructions for making the 21-hydroxylase enzyme. When this enzyme is reduced or absent, the adrenal glands make less cortisol and, in some forms, less aldosterone. The body responds by sending stronger signals to the adrenal cortex, which can cause adrenal cortex hyperplasia and increase production of adrenal androgens. The degree of enzyme activity helps determine whether a person has classic or nonclassic disease.

CAH follows an autosomal recessive inheritance pattern. This means a child usually needs to inherit a disease-causing gene variant from both parents; carriers often have no symptoms themselves. A parent or sibling with CAH can increase the chance that other family members carry a related variant, and ancestry can affect the likelihood of particular variants. CAH is not caused by diet, exercise, stress, or other lifestyle choices, and adrenal gland hyperplasia in this condition is genetic.

Diagnosis may begin with newborn screening for a high level of 17-hydroxyprogesterone. Follow-up blood tests may measure cortisol, aldosterone, renin, adrenal androgens, electrolytes, and other hormones. Results must be interpreted in context because age, sex, illness, and the timing of the sample can affect hormone levels.

Confirming the diagnosis

Clinicians may use genetic testing to identify changes in the CYP21A2 gene and an ACTH stimulation test to assess adrenal hormone production, especially when nonclassic disease is suspected. Electrolyte measurements can help identify salt-wasting disease. A specialist may assess growth, puberty, blood pressure, hydration, and genital development; imaging is generally reserved for situations in which anatomy or another adrenal condition needs clarification.

Hormone replacement

First-line treatment usually includes glucocorticoid replacement to provide cortisol and reduce excess androgen production. People with aldosterone deficiency may also need a mineralocorticoid and, particularly in infancy, salt supplementation. Doses are individualized according to age, symptoms, growth, hormone levels, and illness, and should not be changed without guidance from the clinical team.

People with CAH need sick-day rules for significant illness, injury, or surgery, because the body may need extra cortisol during physical stress. Some patients are prescribed injectable emergency hydrocortisone, and caregivers should learn when and how to use it. Medical identification and an up-to-date emergency plan can help others provide prompt care if needed.

Long-term monitoring and support

Follow-up may include monitoring growth, puberty, blood pressure, electrolytes, hormone levels, bone health, medication effects, and fertility. Endocrinologists may work with pediatricians, gynecologists, urologists, mental health professionals, genetic counselors, and other specialists. Surgery or reproductive care is discussed individually when relevant to a person’s anatomy, symptoms, goals, and preferences.

CAH is a lifelong genetic condition rather than an illness cured by a short treatment course. With appropriate hormone replacement, emergency planning, and regular monitoring, many people can support normal or near-normal development and take part in everyday activities. Outlook varies by the form of CAH, hormone needs, response to treatment, and other individual health considerations.

Contact a clinician about early puberty signs, rapid growth, excessive body hair, irregular periods, fertility concerns, unexplained dehydration, or a family history of CAH. These findings do not always mean a person has CAH, but they may need hormone testing or an endocrinology evaluation. If you or your child has a known diagnosis, keep routine follow-up appointments even when symptoms are well controlled.