A 30-year-old woman with PCOS (BMI 32 kg/m²) is prescribed metformin for insulin resistance. The PRIMARY mechanism by which metformin improves ovulation in PCOS is:

• A Direct suppression of LH secretion from the pituitary
• B Inhibition of aromatase enzyme in ovarian granulosa cells
• C Reduction of hepatic insulin resistance, lowering insulin and androgen levels ✓
• D Stimulation of FSH release from the anterior pituitary

Explanation

Metformin primarily activates AMPK in hepatocytes, reducing hepatic glucose output and improving insulin sensitivity. Lower insulin levels decrease theca cell androgen production (insulin normally amplifies LH-driven androgen synthesis) and reduce LH amplitude indirectly. This reversal of hyperinsulinaemic hyperandrogenaemia restores ovulatory cycles in many PCOS patients. Metformin does not directly suppress LH or stimulate FSH.

Reference: Shaw's Textbook of Gynaecology, 17th ed.

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Written and medically reviewed by the StethoPrep medical team.