A systematic review and meta-analysis of randomized controlled trials comparing pioglitazone versus metformin in the treatment of polycystic ovary syndrome

Objective: Evidence indicates that metformin and pioglitazone both improve insulin resistance and hirsutism among patient with polycystic ovarian syndrome (PCOS). However, the effectiveness of pioglitazone versus metformin in the treatment of PCOS remains controversial. To summarize the relative efficacy of pioglitazone and metformin in PCOS patients, a systematic review and meta-analysis of randomized controlled trials (RCTs) was performed. Methods: The authors searched MEDLINE, EMBASE, CNKI and WANFANG DATA for articles published up to November 2011 to identify those comparing pioglitazone versus metformin as a treatment for PCOS. Results: Of the 161 studies retrieved, six trials were included in this analysis, including a total of 278 women with PCOS. Pioglitazone was found to be significantly more effective than metformin at reducing fasting insulin level (P = 0.002, standardized mean differences [SMD] = -0.37, 95% confidence interval [CI] [-0.61, -0.13]). Similarly, pioglitazone was found to be significantly more effective than metformin at improving the HOMA-IR index (P = 0.014, SMD = -0.32, 95% CI [-0.57, -0.06]). However, pioglitazone was significantly less effective than metformin at reducing body mass index (BMI; P = 0.038, SMD = 0.25, 95% CI [0.01, 0.49]). The effect of pioglitazone on fasting glucose levels, testosterone levels, and Ferriman-Gallwey scores was not significantly different from that of metformin (P greater than 0.05 for all). Conclusion: This systematic review and meta-analysis suggests that pioglitazone was more suitable for treating hyperinsulinemia and insulin resistance among PCOS patients, while metformin was more effective in reducing body weight. Well designed RCTs are needed to provide better evidence.