Uterine effects of metformin administration in anovulatory women with polycystic ovary syndrome

BACKGROUND: Metformin has been shown to improve fertility in anovulatory patients with polycystic ovary syndrome (PCOS), inducing not only a high ovulation and pregnancy rate but also reducing the incidence of miscarriages. The aim of the present study was to evaluate the uterine effects of metformin in patients with PCOS who ovulated under metformin. METHODS: Thirty-seven non-obese primary infertile anovulatory patients with PCOS and another 30 age- and body mass index-matched healthy women (control group) were studied. PCOS patients were treated with metformin (850 mg twice daily) for 6 months, whereas the control group did not receive any treatment. In these PCOS patients who ovulated whilst under metformin treatment (PCOS group) and in controls, uterine, sub-endometrial and endometrial blood flow, and endometrial thickness and pattern were evaluated using serial ultrasonographic assessments. RESULTS: Before treatment, uterine, sub-endometrial and endometrial blood flows were significantly lower in patients with PCOS than in the control group. All indexes of uterine vascularization were significantly improved in the PCOS group with metformin treatment and were not different from the controls. Nor was any difference in endometrial thickness and pattern detected between PCOS and control groups. After grouping the data of PCOS patients who ovulated under metformin for cycles with favourable/unfavourable reproductive outcome, no difference in any parameter was observed. CONCLUSIONS: Metformin improves all surrogate markers of endometrial receptivity in PCOS patients, without difference between patients who had favourable or unfavourable reproductive outcome.