Outlook: metformin use in infertile patients with polycystic ovary syndrome: an evidence-based overview.

Metformin is an insulin sensitizer currently used for treating type-2 diabetes mellitus and recently administered for inducing ovulatory menstrual cycles in oligo-amenorrhoeic patients with polycystic ovary syndrome (PCOS). The aim of the present review is to describe the efficacy of metformin as an ovulation inducer on the basis of the most important evidence-based medicine supported data, including meta-analyses and randomized controlled trials. Specifically, we reviewed the uses of metformin as first- and second-step treatment for PCOS related anovulatory infertility and as co-treatment in infertile PCOS patients who receive gonadotrophins. To date, there is evidence that metformin is effective for restoring normal menstrual cycles in anovulatory PCOS patients, and that it is more effective and cheaper than laparoscopic ovarian drilling as the second therapeutic step in PCOS patients previously defined as resistant to clomiphene citrate. Co-administration of metformin in PCOS patients treated with gonadotrophin improves the mono-ovulation rate and can prevent ovarian hyperstimulation syndrome in patients treated with gonadotrophins for IVF cycles.