Congenital adrenal hyperplasia (CAH)
An inherited group of conditions in which an enzyme needed to make cortisol in the adrenal glands is deficient. This lowers cortisol, drives up 17-hydroxyprogesterone, and diverts the pathway into making excess androgens. Severity ranges from a newborn emergency to a milder adult form.
What it is
Congenital adrenal hyperplasia is a group of inherited disorders present from birth, in which one of the enzymes the adrenal glands need to make cortisol (and sometimes aldosterone) is deficient. The most common cause, by far, is a deficiency of the enzyme 21-hydroxylase. The consequences flow logically from the blocked pathway: cortisol production falls, so the pituitary drives the adrenal glands harder (raising ACTH) and they enlarge (hyperplasia); the steroid building blocks pile up behind the block — especially 17-hydroxyprogesterone — and are diverted into making androgens (male-type hormones). The result depends on how severe the enzyme deficiency is. The severe, 'classic' form appears in newborns and can be life-threatening: it may cause a salt-losing crisis (dangerously low sodium, high potassium, low blood pressure) in the first weeks of life, and in girls can cause ambiguous genitalia from the excess androgens before birth — which is why many countries screen newborns for it. The milder, 'non-classic' form may not appear until later childhood or adulthood, causing early puberty, acne, excess body hair, irregular periods or fertility problems — sometimes mistaken for polycystic ovary syndrome. It is diagnosed largely through a markedly raised 17-hydroxyprogesterone, and managed with hormone replacement (steroids, and salt-retaining hormone in the salt-losing form) under specialist care.
Key lab markers
- 17-hydroxyprogesterone — the key marker; markedly raised because the steroid pathway is blocked at its conversion.
- Cortisol — low or inadequate in the classic form.
- ACTH — raised, as the pituitary drives the under-producing adrenal glands.
- Testosterone and other androgens — often raised from the diverted pathway.
- Sodium and potassium — a salt-losing crisis shows low sodium and high potassium.
- A stimulation (ACTH) test — sometimes needed to confirm the milder form.
Symptoms
- In newborns (classic form): a salt-losing crisis — poor feeding, vomiting, dehydration, low blood pressure
- In baby girls: ambiguous genitalia from excess androgens before birth
- Early or precocious puberty in childhood
- Acne, excess body or facial hair
- Irregular or absent periods, and fertility difficulties
- Rapid growth in childhood but shorter final height
- In the non-classic form: often mild, and mistaken for PCOS
Related lab panels
When to discuss with a doctor
The severe form of CAH is a newborn matter — a salt-losing crisis in the first weeks of life is a medical emergency, and newborn screening (which measures 17-hydroxyprogesterone) exists to catch it early. Beyond infancy, CAH should be considered when there are signs of excess androgens that don't fit the usual picture — such as early puberty in a child, or acne, excess hair and irregular periods in a young woman where the pattern is unusual for polycystic ovary syndrome. A markedly raised 17-hydroxyprogesterone points to it and leads to specialist (endocrine) assessment, sometimes with a stimulation test to confirm the milder form. People with CAH are managed lifelong by an endocrinologist with hormone replacement, and need extra steroid cover during illness. Mediora.AI can surface a raised 17-hydroxyprogesterone alongside cortisol, ACTH and androgens that points toward CAH; the diagnosis and treatment belong with your doctor and an endocrinologist.