Metformin decreases thyrotropin in overweight women with polycystic ovarian syndrome and hypothyroidism.

OBJECTIVE

To assess the effect of metformin administration on thyroid function in overweight women with polycystic ovarian syndrome (PCOS).

METHODS

Twenty-seven overweight women with PCOS and hypothyroidism were selected. Fifteen patients (group I) were treated with metformin 1500 mg/day for 6 months and 12 patients (group II) with placebo. Serum thyrotropin (TSH), free T3 and free T4 were measured at baseline and 6 months after the beginning of the study.

RESULTS

A significant decrease (p<0.001) in TSH levels was observed in group I but not in group II subjects after 6 months of metformin treatment. No significant change in free T3 and free T4 was observed throughout the study in any group.

CONCLUSIONS

In obese PCOS patients with primary hypothyroidism, metformin results in a significant fall and sometimes normalisation of TSH, without causing any reciprocal changes in other thyroid function parameters.