For women with PCOS, metformin lowers the male hormone testosterone — but only in those with PCOS, not in other obese women — showing it targets the root cause of symptoms like facial hair.

Even women without PCOS who are obese and take metformin with a diet lose weight and belly fat, and their SHBG (a hormone that binds male hormones) goes up — but their male hormone levels don’t drop like in women with PCOS.

Metformin lowers leptin — the ‘satiety hormone’ — in obese women, even when they lose the same amount of weight as those not taking it, meaning it might directly affect how the body regulates hunger.

For obese women with PCOS, taking metformin along with a low-calorie diet helps them lose more weight, shrink belly fat, lower male hormone levels, and get more regular periods than just dieting alone.