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 (beta=-1.60, 95% CI:-2.30 to -0.90, P=0.003; beta=0.20, 95% CI: 0.80-0.32, P=0.004, respectively) and controls (beta=-2.36, 95% CI: -3.38 to -1.33, P=0.003; beta=0.11, 95% CI: 0.00-0.21, P=0.05, respectively) and of total calcium and luteinising hormone in PCOS cases (beta=2.43, 95% CI: 1.67-3.19, P=0.005; beta=-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.