Descriptive review of the evidence for the use of metformin in polycystic ovary syndrome.

Use of metformin in polycystic ovary syndrome (PCOS) is becoming increasingly accepted and widespread, but clinical practice is ahead of the evidence. Although a wide range of benefits in metabolic, reproductive, and clinical measures have been reported from non-randomised trials with metformin, close inspection of results from the adequately controlled studies shows that the benefits are modest. Our aim in this descriptive review is not to define practice guidelines but to improve clinicians' knowledge of the available published clinical evidence, concentrating on the few randomised controlled trials. We also highlight other issues, including hirsutism, acne, pregnancy, and neonatal outcome, that require more attention before clinical recommendations for the use of metformin in PCOS can be formalised. The potentially greater benefits achievable by lifestyle changes alone are also emphasised. We hope that the review will lead to more judicious use of metformin in PCOS and a more structured approach to research.