Blood Trace Element Concentrations in Polycystic Ovary Syndrome: Systematic Review and Meta-analysis.

Polycystic ovary syndrome (PCOS) is a prevalent condition in women of reproductive age. PCOS is characterized by androgen excess and chronic anovulation and associated with low-grade inflammation and metabolic comorbidities. Some trace elements have been linked to pathophysiological mechanisms of oxidative stress and inflammation in different disorders. Therefore, we conducted a systematic review and meta-analysis of the available evidence regarding trace element concentrations in PCOS. We reviewed MEDLINE and EMBASE in search of case-control, cross-sectional, and cohort studies published until September 2015. Of 183 studies identified, six were selected for systematic review. All used the Rotterdam criteria for the diagnosis of PCOS. Two studies evaluating chromium and one assessing cobalt levels did not observe differences between PCOS and controls. Another study recorded similar nickel and vanadium levels between the groups, but lower selenium concentrations in women with PCOS compared to controls. Four studies were included in the random effects model meta-analysis, for a total of 264 PCOS and 151 control women. Copper levels were found to be higher in women with PCOS than in controls [mean difference 0.12 ppm (95 % CI 0.07; 0.17 ppm); I 2  = 0 %]. Manganese [mean difference 0.04 ppm (95 % CI -0.05; 0.13 ppm); I 2  = 94.4 %] and zinc concentrations [mean difference 0.02 ppm (95 % CI -0.12; 0.16 ppm); I 2  = 92.4 %] were similar between the groups. The present results suggest a relationship between increased copper concentration and PCOS. This systematic review and meta-analysis is registered in PROSPERO under number CRD42016034036.