Increasing evidence supports the contribution of vitamin D deficiency (VDD) in metabolic disturbances among women with polycystic ovary syndrome (PCOS). This review aims to assess the associations between vitamin D levels and metabolic/endocrine dysregulations and to determine the effects of vitamin D supplementation on glucose metabolism, insulin sensitivity, lipid profile, and hormones functionality in PCOS patients. We searched in PubMed human randomized controlled trials (RCTs) published in English between 2016 and 2019 on the effects of vitamin D supplementation on PCOS. Nine studies were included and analyzed. Vitamin D supplementation restored physiological serum 25(OH)D levels in PCOS women in all the studies included. In six studies, it significantly decreased fasting plasma glucose and brought to improvements in insulin resistance (IR) and serum fasting insulin. In addition, four studies reported decreases of serum triglycerides, while discordant data are reported as far as LDL, HDL, and total cholesterol levels. High-doses of vitamin D (4000 IU), compared with low-dose (1000 IU), and placebo, showed beneficial effects on total testosterone, sex hormone-binding globulin (SHBG) and free androgen index (FAI). Vitamin D supplementation at high doses for a period of at least 12 weeks, may lead to improvement in terms of glucose level, insulin sensitivity, hyperlipidemia, and hormonal functionality in PCOS women.
Keywords: Vitamin D; hyperandrogenism; hyperlipidemia; insulin resistance; polycystic ovary syndrome.