Effect of metformin on PCOS

Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting 6% of women of reproductive age. Its clinical manifestations include oligomenorrhea, amenorrhea paired with infertility, hirsutism, acne and alopecia. PCOS-affected women are also known to suffer from insulin resistance (IR) and obesity. Many intervention studies have demonstrated the positive effect of metformin on the reproductive and metabolic aspects of PCOS. However the mechanisms underlying the beneficial effects of metformin in the treatment of PCOS are not fully understood. As not all PCOS patients are obese or insulin resistant, it is not clear whether PCOS patients without IR also benefit from a therapy with insulin sensitizers. Tan et al carried out this study to determine the effect of metformin on 3 groups of patients totalling 188 and grouped according to their BMI as lean, overweight and obese. Metformin significantly improved all outcome parameters except fasting glucose levels. In patients who were lean and without pre-treatment insulin resistance, metformin improved HOMA-IR (homeostasis model assessment for IR), fasting insulin levels, testosterone levels, ovulation rate and acne. The authors conclude that while the exact mechanism of metformin action remains unclear it appears that besides reducing IR and thus hyperinsulinemia, metformin has significant effects that are independent of the patient’s pre-treatment IR status. S Tan, S Hahn, S Benson, T Dietz, H Lahner, L C Moeller, M Schmidt, S Elsenbruch, R Kimming, K Mann & O E Janssen. Metformin improves polycystic ovary syndrome symptoms irrespective of pre-treatment insulin resistance. European Journal of Endocrinology, 2007, 157, 671-678.