Rotterdam criteria for PCOS require two of three features. A 26-year-old woman has oligomenorrhoea and ultrasound showing polycystic ovarian morphology (PCOM) but normal androgens. She has PCOS by Rotterdam criteria. Which additional investigation is most important before starting metformin?
- A Fasting serum insulin level
- B 75g OGTT with 2-hour glucose ✓
- C Serum LH:FSH ratio
- D Anti-Müllerian hormone (AMH) level
Correct answer: B. 75g OGTT with 2-hour glucose
Explanation
Before initiating metformin in PCOS, screening for glucose intolerance and type 2 diabetes is essential. A 75g oral glucose tolerance test (OGTT) is the recommended investigation as fasting glucose alone misses impaired glucose tolerance. LH:FSH ratio supports diagnosis but is not required by Rotterdam criteria and does not influence metformin decision. AMH reflects ovarian reserve and PCOM severity but does not guide metformin initiation. Fasting insulin does not have standardised diagnostic thresholds.
Reference: Shaw's Textbook of Gynaecology, 17th ed.
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