Biochemistry · Enzyme
11β-Hydroxylase (CYP11B1) !
It makes the last step of cortisol in fasciculata mitochondria; its deficiency causes adrenal hyperplasia with hypertension.
Updated 2026-11-01
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Key facts
- 11-Deoxycortisol → cortisol and 11-deoxycorticosterone → corticosterone.
- A mitochondrial P450: it receives electrons from adrenodoxin and adrenodoxin reductase (NADPH).
- It is 93 % identical to aldosterone synthase (CYP11B2), its neighbour on chromosome 8, which finishes aldosterone in the glomerulosa.
- Structure 6M7X is human CYP11B1 with fadrozole, an imidazole inhibitor bound to the haem iron.
Regulation
- ACTH (cAMP/PKA) raises its expression; cortisol slows it indirectly by lowering ACTH.
- It is expressed in the fasciculata, not in the glomerulosa.
Inhibitors and toxins
- Metyrapone (diagnostic test and treatment of cortisol excess)
- Osilodrostat
- Etomidate (anaesthetic: can suppress cortisol)
- Ketoconazole (inhibits several adrenal P450 enzymes)
Clinical notes
- Its deficiency piles up 11-deoxycortisol and 11-deoxycorticosterone: hypertension with low potassium and suppressed renin, plus virilisation.
- A hybrid CYP11B1/CYP11B2 gene puts aldosterone synthase under ACTH control: familial hyperaldosteronism type I, which responds to glucocorticoids.
- Inhibitors of this enzyme are used to control Cushing syndrome.
Pathways
Related conditions
- Congenital adrenal hyperplasia due to 11β-hydroxylase deficiency
- Cushing syndrome
- Arterial hypertension
Related
- Adrenal enzymes and congenital adrenal hyperplasia
- Cortisol
- Aldosterone
- 21-Hydroxylase (CYP21A2)
- Steroid hormone synthesis (overview)
Test yourself
Think of the answer, then tap the question to see it.
Which step of cortisol synthesis does 11β-hydroxylase catalyse?
The last one: it turns 11-deoxycortisol into cortisol.
Why does its deficiency cause hypertension?
11-Deoxycorticosterone piles up; it acts as a mineralocorticoid and retains sodium.
Which drug inhibits 11β-hydroxylase and is used to test the adrenal axis?
Metyrapone.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: CYP11B1: Cytochrome P450 11B1, mitochondrial (human) (UniProt, 2026); CYP11B1 gene: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); 6M7X: Structure of human CYP11B1 in complex with fadrozole (RCSB Protein Data Bank, 2026); Congenital adrenal hyperplasia due to 11-beta-hydroxylase 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.