AKT · Endocrine/Adrenallow yield

Congenital adrenal hyperplasia

Enzyme deficiency in cortisol synthesis (commonly 21-hydroxylase) → androgen excess

Overview

Autosomal-recessive deficiency of a cortisol-synthesis enzyme (21-hydroxylase in ~90%), shunting precursors into androgens. Loss of cortisol ± aldosterone with androgen excess: classically a salt-wasting crisis and virilised (ambiguous) genitalia in a neonate. Managed with glucocorticoid (± mineralocorticoid) replacement. (Carded in depth on child health — referenced here for the adrenal axis.)

Recognise

Classic salt-wasting (neonate): vomiting, dehydration, hyponatraemia + HYPERkalaemia, hypoglycaemia, hypotension in the first weeks
Virilisation: ambiguous genitalia in a female neonate; precocious puberty/tall-then-short stature in milder forms
21-hydroxylase deficiency: raised 17-hydroxyprogesterone

Red flags

Salt-wasting adrenal crisis in a neonate → emergency (fluids, IV hydrocortisone, correct glucose/electrolytes)

Differentials & how to tell them apart

Primary adrenal insufficiency (other)no androgen excess/virilisation

Pyloric stenosisvomiting with HYPOkalaemic HYPOchloraemic alkalosis (opposite electrolytes), no virilisation

Other causes of ambiguous genitaliakaryotype/hormonal profile

Investigations

Raised 17-hydroxyprogesterone (newborn screening in some regions), U&Es (↓Na ↑K), glucose; karyotype/genetics; synacthen if needed.

Management

Glucocorticoid (± mineralocorticoid) replacement; crisis = IV hydrocortisone + fluids

1Neonatal crisis → IV fluids, hydrocortisone, correct glucose/electrolytes. Maintenance glucocorticoid ± fludrocortisone, monitored by paediatric endocrinology.Gate: A virilised female neonate or a salt-wasting crisis (↓Na/↑K) is CAH until excluded — measure 17-hydroxyprogesterone; don't mistake the electrolytes for pyloric stenosis (which is the opposite alkalosis)
2Lifelong replacement with stress dosing; genital reconstruction decisions; genetic counselling. (See child_health for full paediatric detail.)

Glucocorticoid (hydrocortisone) replacement — replaces cortisol and suppresses ACTH-driven androgen excess

Fludrocortisone (+ salt) — for salt-wasting (mineralocorticoid) forms

Key points

Salt-wasting crisis (↓Na, ↑K) + virilised genitalia + raised 17-OHP = 21-hydroxylase CAH. Contrast the electrolytes with pyloric stenosis. (Full paediatric teaching is on child health.)

Monitor & prognosis

Growth, 17-OHP/androgens, electrolytes.

Good with replacement.

Source: BSPED; cross-ref child_health