A 26-year-old woman has irregular cycles and elevated serum total testosterone of 4.8 nmol/L. Androgen excess work-up also shows elevated DHEAS and 17-hydroxyprogesterone (17-OHP) at 12 nmol/L (normal <6 nmol/L). The most likely underlying diagnosis causing her hyperandrogenism with elevated 17-OHP is:
- A Non-classical congenital adrenal hyperplasia (NCCAH) due to 21-hydroxylase deficiency ✓
- B Polycystic ovary syndrome
- C Androgen-secreting adrenal adenoma
- D Cushing's syndrome
Correct answer: A. Non-classical congenital adrenal hyperplasia (NCCAH) due to 21-hydroxylase deficiency
Explanation
Non-classical (late-onset) congenital adrenal hyperplasia due to 21-hydroxylase deficiency (CYP21A2 mutation) presents in adolescence or adulthood with hyperandrogenism (hirsutism, acne, menstrual irregularity) mimicking PCOS. The biochemical hallmark is elevated basal 17-OHP (>6 nmol/L or >2 ng/mL), which accumulates proximal to the enzymatic block. Stimulated 17-OHP >30 nmol/L after ACTH stimulation confirms the diagnosis. PCOS does not cause elevated 17-OHP. An androgen-secreting adenoma would show markedly elevated DHEAS (usually >18 µmol/L) without 17-OHP elevation.
Reference: Shaw's Textbook of Gynaecology, 17th ed.
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