Metformin improves endothelial function in normoinsulinemic PCOS patients: a new prospective

Metformin was reported to improve the alterations of endothelial reactivity in normal-weight subjects with polycystic ovary syndrome (PCOS). The aim of the present study was to investigate the mechanisms of action of this drug on the vascular function of this population.

Thirteen normal-weight, normoinsulinemic and normolipemic PCOS women were studied before and after 6 months of metformin treatment (1000 mg/day). The endothelial function was assessed by evaluating the flow-mediated dilatation (FMD) of the brachial artery. We correlated this parameter with the endocrine-metabolic features of the patients.

Metformin significantly reduced testosterone (1.56 +/- 0.52 after 6 months versus 2.98 +/- 1.00 at baseline) and 17-hydroxyprogesterone (0.03 +/- 0.01 versus 0.06 +/- 0.02 nmol/ml) levels, without affecting gluco-insulinemic parameters. Concomitantly, the basal vessel diameter and the FMD significantly increased (4.12 +/- 0.68 versus 3.2 +/- 0.41 and 5.2 +/- 0.6 versus 3.76 +/- 0.5 mm, respectively), thus documenting an improved endothelial function.

Our data confirm the positive effects of metformin on the altered vascular reactivity, a precocious marker of cardiovascular risk, in normoinsulinemic PCOS subjects. This improvement seems to be mediated through hormonal changes, thus highlighting the detrimental role of hyperandrogenemia on the endothelial function, even beyond the metabolic factors. However, a direct effect of metformin on the endothelium should not be excluded.