Leptin Levels in Women With Polycystic Ovary Syndrome: A Systematic Review and a Meta-Analysis

Objective: Conflicting results regarding leptin levels in women with polycystic ovary syndrome (PCOS) have been reported. We summarize all available evidence from human participant studies to evaluate leptin levels in PCOS. Data Sources: PubMed, ClinicalTrials.gov, and Web of Science databases were searched with English-language restriction for only human beings from the inception to December 31, 2015. Search terms included PCOS (polycystic ovary syndrome or PCOS) and leptin. Methods of Study Selection: A total of 238 studies were reviewed, and a total of 19 studies, involving 991 women with PCOS and 898 controls, were eligible for our meta-analysis. Studies were eligible if provided leptin means and standard deviation in women with PCOS and healthy women controls. Results: Parameters, such as body mass index, insulin resistance (IR), and total testosterone, which may influence leptin levels were extracted. Data were collected and analyzed by RevMan 5.3 and Stata/SE14.0. The pooling analysis of all relevant studies revealed that leptin levels were significantly higher in patients with PCOS than in controls, with standardized mean difference of 1.62 (95% confidence interval: 1.01-2.23). However, the heterogeneity across studies was considerable and not eliminated in subgroup analyses. Meta-regression analysis further suggested that the heterogeneity might be relevant to variability in IR and study location. Conclusion: Elevated leptin levels are detected in women with PCOS compared with non-PCOS controls. Higher leptin levels may be correlated with IR, metabolic disorder, infertility, and even cardiovascular disease risk in PCOS, which may contribute to the etiology and development of PCOS.