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# Congenital adrenal hyperplasia due to 17α-hydroxylase deficiency

A very rare adrenal hyperplasia: no sex hormones are made and hypertension with low potassium appears, usually found in adolescence.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Right adrenal gland](https://durgical.com/en/anatomy/suprarenal-gland-abdomen/)
- [Left adrenal gland](https://durgical.com/en/anatomy/suprarenal-gland/)
- [Kidneys](https://durgical.com/en/anatomy/kidney/)
- [Ovaries](https://durgical.com/en/anatomy/ovary/)
- [Testes](https://durgical.com/en/anatomy/testis/)

## In biochemistry

- [Adrenal cortisol synthesis: Step 3 · 17α-Hydroxylase/17,20-lyase (CYP17A1)](https://durgical.com/en/biochemistry/pathways/adrenal-cortisol-synthesis/#paso-3)
- [Adrenal enzymes and congenital adrenal hyperplasia](https://durgical.com/en/biochemistry/topics/adrenal-enzymes-and-congenital-adrenal-hyperplasia/)
- [17α-Hydroxylase/17,20-lyase (CYP17A1)](https://durgical.com/en/biochemistry/enzymes/17-hydroxylase-17-20-lyase/)

## In embryology

- [Differences of sex development: CAH, AIS and 5α-reductase](https://durgical.com/en/embryology/differences-of-sex-development-cah-ais-and-5-reductase/)

## In physiology

- [The adrenal cortex: zones, hormones and androgens](https://durgical.com/en/physiology/the-adrenal-cortex-zones-hormones-and-androgens/)

## What it is

An autosomal recessive disorder from CYP17A1 variants that blocks cortisol, androgen and oestrogen synthesis and diverts precursors into mineralocorticoids.

## Who gets it

It accounts for about 1 % of congenital adrenal hyperplasia and is estimated at 1 in a million people worldwide. No Colombian figures are cited here.

## Causes

- Variants in both copies of CYP17A1 (chromosome 10)
- Autosomal recessive inheritance

## Risk factors

- Carrier parents
- Consanguinity

## Pathophysiology

CYP17A1 has 17α-hydroxylase (cortisol pathway) and 17,20-lyase (androgen pathway) activity. Without it pregnenolone can only follow the mineralocorticoid branch: 11-deoxycorticosterone and corticosterone pile up. DOC retains sodium (hypertension, low potassium, suppressed renin and aldosterone); corticosterone has enough glucocorticoid action, so adrenal crisis is rare. Neither the adrenals nor the gonads make androgens or oestrogens: a 46,XY fetus is not virilised (female or ambiguous external genitalia, internal testes) and puberty is absent in both sexes.

## Classification

- Combined 17α-hydroxylase and 17,20-lyase deficiency (classic)
- Isolated 17,20-lyase deficiency (rare)

## Symptoms and signs

- No pubertal development and primary amenorrhoea
- In 46,XY: female or ambiguous external genitalia with testes in the [abdomen](https://durgical.com/en/anatomy/region/abdomen/) or groin
- High blood pressure
- Muscle weakness from low potassium
- Tall stature with eunuchoid proportions and delayed bone age

## Red flags

- A teenager with hypertension and hypokalaemia
- Absent puberty with high gonadotropins
- An inguinal mass in a girl (possible testis)

## Diagnosis

**Clinical**
Suspected in an adolescent girl without puberty, with hypertension and low potassium.

**Tests**
High 11-deoxycorticosterone and corticosterone; low cortisol, androgens and oestrogens; high LH and FSH; low renin and aldosterone; low potassium; karyotype (46,XX or 46,XY); CYP17A1 genetic testing.

**Imaging**
Pelvic ultrasound or MRI to look for a uterus, [ovaries](https://durgical.com/en/anatomy/ovary/) or intra-abdominal [testes](https://durgical.com/en/anatomy/testis/); bone densitometry; hand X-ray for bone age.

## Treatment

**Medical**
Glucocorticoid replacement to hold ACTH back and lower DOC

**Medical**
Sex hormone replacement from pubertal age according to the gender of rearing; antihypertensives if needed

**Surgical**
Removal of intra-abdominal testes in 46,XY people raised as women, because of tumour risk

**Follow-up**
Monitoring of blood pressure, potassium and bone mass, and psychological support

## Complications

- Chronic hypertension and cardiovascular damage
- Osteoporosis from lack of oestrogen
- Infertility
- Tumours in undescended testes

## Prognosis

Good with hormone treatment and blood pressure control; fertility is usually very limited.

## Prevention

- Genetic counselling in affected families

## Test yourself

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

## Why does 17α-hydroxylase deficiency cause hypertension?

Because precursors are diverted to 11-deoxycorticosterone, a mineralocorticoid that retains sodium.

## Why is adrenal crisis rare in this deficiency?

Because the piled-up corticosterone has enough glucocorticoid activity.

## How does a 46,XY person with this deficiency present?

With female or ambiguous external genitalia, internal testes and absent puberty.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/conditions/congenital-adrenal-hyperplasia-due-to-17-hydroxylase-deficiency/)

## Related conditions

- [Congenital adrenal hyperplasia due to 21-hydroxylase deficiency](https://durgical.com/en/conditions/congenital-adrenal-hyperplasia-due-to-21-hydroxylase-deficiency/)
- [Congenital adrenal hyperplasia due to 11β-hydroxylase deficiency](https://durgical.com/en/conditions/congenital-adrenal-hyperplasia-due-to-11-hydroxylase-deficiency/)
- [Arterial hypertension](https://durgical.com/en/conditions/arterial-hypertension/)
- [Osteoporosis](https://durgical.com/en/conditions/osteoporosis/)

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

Sources: [17 alpha-hydroxylase/17,20-lyase deficiency: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/17-alpha-hydroxylase-17-20-lyase-deficiency/) (MedlinePlus, US National Library of Medicine, 2026); [CYP17A1 gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/cyp17a1/) (MedlinePlus, US National Library of Medicine, 2026); [Congenital adrenal hyperplasia: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000411.htm) (MedlinePlus, US National Library of Medicine, 2026).

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Source: https://durgical.com/en/conditions/congenital-adrenal-hyperplasia-due-to-17-hydroxylase-deficiency/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/congenital-adrenal-hyperplasia-due-to-17-hydroxylase-deficiency/