Insulin resistance in obesity and polycystic ovary syndrome: systematic review and meta-analysis of observational studies

We aimed at investigating whether insulin resistance (IR)/sensitivity are impaired in obese/non-obese polycystic ovary syndrome (PCOS) and obese/non-obese healthy controls. A comprehensive literature search was performed for observational, English language studies. Meta-analysis was performed with the random effects model according to the heterogeneity. Eligible studies, involving 3037 women in four groups of: 1-obese, PCOS; 2-non-obese, PCOS, 3-obese, non-PCOS and 4-Non-obese, non-PCOS were included. Based on the insulin resistance index (HOMA-IR) analysis, the pooled mean (95% Conf. Interval) of HOMA IR in groups 1-4 were 4.38 (3.84, 4.92), 2.68 (2.16, 3.20), 2.44 (2.06, 2.82) and 1.34 (1.06, 1.63), respectively. Meta-analysis showed that group 1 (obese, PCOS patients) statistically have the highest IR and group 4 (non-obese, non-PCOS women) have the highest insulin sensitivity. Group 2 (non-obese, PCOS patients) and group 3 (obese, non-PCOS women) were between this range and they had lower IR than group 1 (obese, PCOS) and lower insulin sensitivity than group 4 (non-obese, non-PCOS). So, there were statistical differences between all groups except between groups 2 and 3. Insulin sensitivity indexes (quickie and ISI), also confirm the IR index (HOMA-IR) results. Based on different IR/sensitivity indexes, we found no evidence of any different effects of BMI ≥ 30 kg/m(2) on IR/sensitivity. In conclusion, PCOS status intensifies the adverse effects of obesity on IR, it has to be appropriately addressed in primary and secondary preventive cares and treatments provided for these women.