Treatment of polycystic ovary syndrome (PCOS) with metformin ameliorates insulin resistance in parallel with the decrease of serum interleukin-6 concentrations.

Low-grade chronic inflammation underlies the pathogenesis of insulin-resistant disorders such as polycystic ovary syndrome (PCOS). We aimed to study if the changes observed in the insulin sensitivity of PCOS patients during treatment with oral contraceptives or metformin associate changes in the serum inflammatory markers interleukin-6 (IL-6) and interleukin-18 (IL-18). In a randomized open-label clinical trial (NLM Identifier NCT00428311), 34 PCOS patients were allocated to receive oral treatment with metformin (850  mg twice daily) or with the Diane (35) Diario contraceptive pill (35 μg of ethynylestradiol plus 2 mg of cyproterone acetate) for 24 weeks. Changes in serum IL-6 and IL-18 levels and insulin sensitivity index were monitored throughout the study. Eighteen women without hyperandrogenism served as controls for serum interleukin concentrations. PCOS women treated with metformin showed a decrease in IL-6 levels throughout the study compared with women treated with Diane (35) Diario (-33% change vs. +23% change, F=3.709, p=0.048; intention-to-treat analysis: F=5.569, p=0.011). There were no statistically significant changes in IL-18 concentrations with any treatment. The decrease in IL-6 levels in women receiving metformin occurred in parallel to the increase in the insulin sensitivity index (r=-0.579, p=0.048; intention-to-treat analysis, r=-0.687, p=0.001). In conclusion, serum IL-6 levels decreased during treatment with metformin in parallel to amelioration of insulin resistance, whereas oral contraceptives slightly increased circulating IL-6 levels without changing insulin sensitivity. Both drugs had a neutral effect on serum IL-18 concentrations.