Vitamin D predictors in polycystic ovary syndrome: a meta-analysis

BACKGROUND: The aim of this meta-analysis was to examine differences and predictors of serum 25-hydroxyvitamin D concentrations in women with polycystic ovary syndrome (PCOS) compared with non-PCOS controls matched for body mass index. MATERIALS AND METHODS: Three databases were searched (2003-2015) to retrieve studies that evaluated serum 25-hydroxyvitamin D in PCOS women and controls. Meta-regression analysis was performed with anthropometric and metabolic/endocrine parameters as covariates. RESULTS: Fourteen studies that included 2262 women (1150 PCOS patients/1162 controls) were eligible. Serum 25-hydroxyvitamin D, follicle-stimulating hormone and sex hormone-binding globulin were significantly lower in patients with PCOS than controls. Homoeostatic model assessment-insulin resistance index, serum insulin, total cholesterol, triglycerides, low-density lipoprotein cholesterol, luteinising hormone and testosterone were significantly higher in patients with PCOS compared to controls. Meta-regression analysis demonstrated significant effects of waist-to-hip ratio and glucose in PCOS women (β = -1·60, 95% CI: -2·30 to -0·90, P = 0·003; β = 0·20, 95% CI: 0·80-0·32, P = 0·004, respectively) and controls (β = -2·36, 95% CI: -3·38 to -1·33, P = 0·003; β = 0·11, 95% CI: 0·00-0·21, P = 0·05, respectively) and of total calcium and luteinising hormone in PCOS cases (β = 2·43, 95% CI: 1·67-3·19, P = 0·005; β = -0·37, 95% CI: -0·68 to -0·06, P = 0·03, respectively). CONCLUSIONS: Serum 25-hydroxyvitamin D may be predicted positively by serum calcium and negatively by luteinising hormone in women with PCOS, and negatively by waist-to-hip ratio and positively by fasting glucose in both PCOS and non-PCOS women, independently of the presence of obesity.