Adrenal enzymes and congenital adrenal hyperplasia !

Which adrenal cortex enzyme makes each hormone, and what happens when one is missing: what comes before piles up and spills into another branch.

Updated 2026-11-01

Key facts

Three branches from pregnenolone: mineralocorticoids (glomerulosa), glucocorticoids (fasciculata) and androgens (reticularis).
17α-Hydroxylase (CYP17A1) picks the branch: without it pregnenolone can only go towards aldosterone.
In every CAH cortisol is short, ACTH rises and enlarges the gland; the precursors before the block pile up.
21-Hydroxylase deficiency (95 %): salt loss and virilisation. 11β deficiency: virilisation and hypertension. 17α deficiency: hypertension with no androgens or oestrogens.
Rule of thumb: the deficiency that ends in 1 (21, 11β) virilises; the one that starts with 1 (11β, 17α) causes hypertension.

Mineralocorticoid branch: pregnenolone → (3β-HSD2) progesterone → (CYP21A2) 11-deoxycorticosterone (DOC) → (CYP11B2) corticosterone → aldosterone.
Glucocorticoid branch: pregnenolone → (CYP17A1, 17α-hydroxylase) 17-hydroxypregnenolone → (3β-HSD2) 17-hydroxyprogesterone → (CYP21A2) 11-deoxycortisol → (CYP11B1) cortisol.
Androgen branch: 17-hydroxypregnenolone → (CYP17A1, 17,20-lyase) DHEA → androstenedione → testosterone; aromatase turns androgens into oestrogens.
21-Hydroxylase deficiency: 17-hydroxyprogesterone piles up and spills into androgens; in the salt-wasting form aldosterone is also missing (low sodium, high potassium, high renin).
11β-Hydroxylase deficiency: 11-deoxycortisol and DOC pile up; DOC acts as a mineralocorticoid and causes hypertension with low potassium and suppressed renin; androgens also rise.
17α-Hydroxylase deficiency: no cortisol, androgens or oestrogens are made; everything goes to DOC and corticosterone (hypertension, hypokalaemia). Corticosterone partly stands in for cortisol, so adrenal crisis is rare.
Rarer forms: 3β-HSD2, StAR (lipoid hyperplasia, no steroid hormones at all) and P450 oxidoreductase (POR) deficiencies.
The shared treatment is glucocorticoid replacement: it corrects cortisol and, by holding ACTH back, lowers the piled-up precursors.

Newborn screening measures 17-hydroxyprogesterone in heel-prick blood to find 21-hydroxylase deficiency before the salt-wasting crisis.
A newborn girl with ambiguous genitalia and a normal uterus and ovaries: think first of 21-hydroxylase deficiency.
A teenager with hypertension, low potassium and no puberty: think of 17α-hydroxylase deficiency.
Metyrapone inhibits 11β-hydroxylase and is used to test the axis and to treat cortisol excess.

Think of the answer, then tap the question to see it.

Why does the adrenal gland enlarge in congenital adrenal hyperplasia?

Because cortisol is short, the pituitary is not held back and the high ACTH keeps stimulating the cortex.

Which precursor piles up in 21-hydroxylase deficiency and is used for screening?

17-Hydroxyprogesterone, which also spills into androgens.

Why does 11β-hydroxylase deficiency cause hypertension?

11-Deoxycorticosterone piles up; it has mineralocorticoid action and retains sodium.

Which hormones are missing in 17α-hydroxylase deficiency?

Cortisol, androgens and oestrogens; production is diverted to DOC and corticosterone.

Which treatment fixes both the cortisol shortage and the precursor excess?

Glucocorticoid replacement, which holds ACTH back.

Educational information, not medical advice. For any symptom, see a health professional.

Sources: Congenital adrenal hyperplasia: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); 21-hydroxylase deficiency: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Congenital adrenal hyperplasia due to 11-beta-hydroxylase deficiency: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); 17 alpha-hydroxylase/17,20-lyase deficiency: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Representative model, for educational purposes only.