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[Biochemistry](https://durgical.com/en/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.

**Also called**
P450c11, Steroid 11β-monooxygenase

**EC number**
[1.14.15.4](https://www.enzyme-database.org/query.php?ec=1.14.15.4)

**Genes**
CYP11B1

**Structure (PDB)**
[6M7X](https://www.rcsb.org/structure/6M7X)

## 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

- [Adrenal cortisol synthesis](https://durgical.com/en/biochemistry/pathways/adrenal-cortisol-synthesis/)

## Related conditions

- [Congenital adrenal hyperplasia due to 11β-hydroxylase deficiency](https://durgical.com/en/conditions/congenital-adrenal-hyperplasia-due-to-11-hydroxylase-deficiency/)
- [Cushing syndrome](https://durgical.com/en/conditions/cushing-syndrome/)
- [Arterial hypertension](https://durgical.com/en/conditions/arterial-hypertension/)

## Related

- [Adrenal enzymes and congenital adrenal hyperplasia](https://durgical.com/en/biochemistry/topics/adrenal-enzymes-and-congenital-adrenal-hyperplasia/)
- [Cortisol](https://durgical.com/en/biochemistry/molecules/cortisol/)
- [Aldosterone](https://durgical.com/en/biochemistry/molecules/aldosterone/)
- [21-Hydroxylase (CYP21A2)](https://durgical.com/en/biochemistry/enzymes/21-hydroxylase/)
- [Steroid hormone synthesis (overview)](https://durgical.com/en/biochemistry/topics/steroid-hormone-synthesis/)

## 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.

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

Sources: [CYP11B1: Cytochrome P450 11B1, mitochondrial (human)](https://www.uniprot.org/uniprotkb/P15538/entry) (UniProt, 2026); [CYP11B1 gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/cyp11b1/) (MedlinePlus, US National Library of Medicine, 2026); [6M7X: Structure of human CYP11B1 in complex with fadrozole](https://www.rcsb.org/structure/6M7X) (RCSB Protein Data Bank, 2026); [Congenital adrenal hyperplasia due to 11-beta-hydroxylase deficiency: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/congenital-adrenal-hyperplasia-due-to-11-beta-hydroxylase-deficiency/) (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.

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