Effect of Two Different Doses of Vitamin D Supplementation on Metabolic Profiles of Insulin-Resistant Patients with Polycystic Ovary Syndrome

This study was carried out to evaluate the effects of vitamin D supplementation on the metabolic profiles of insulin-resistant subjects with polycystic ovary syndrome (PCOS). This randomized double-blind, placebo-controlled trial was conducted on 90 insulin-resistant women with PCOS. Participants were randomly assigned to three groups to intake either 4000 IU of vitamin D or 1000 IU of vitamin D or placebo (n = 30 each group) daily for 12 weeks. Vitamin D supplementation (4000 IU), compared with vitamin D (1000 IU) and placebo, led to significant reductions in total testosterone (−0.2 ± 0.2 vs. −0.1 ± 0.6 and +0.1 ± 0.2 ng/mL, respectively, p = 0.02), free androgen index (FAI) (−0.06 ± 0.12 vs. −0.02 ± 0.12 and +0.004 ± 0.04, respectively, p = 0.04), hirsutism (−1.1 ± 1.1 vs. −0.8 ± 1.2 and −0.1 ± 0.4, respectively, p = 0.001) and high-sensitivity C-reactive protein (hs-CRP) (−0.7 ± 1.4 vs. −0.5 ± 0.9 and +0.5 ± 2.4 mg/L, respectively, p = 0.01). In addition, we found significant elevations in mean change of sex hormone-binding globulin (SHBG) (+19.1 ± 23.0 vs. +4.5 ± 11.0 and +0.7 ± 10.4 nmol/L, respectively, p < 0.001) and total antioxidant capacity (TAC) (+130 ± 144 vs. +33 ± 126 and −36 ± 104 mmol/L, respectively, p < 0.001) in the high-dose vitamin D group compared with low-dose vitamin D and placebo groups. Overall, high-dose vitamin D administration for 12 weeks to insulin-resistant women with PCOS had beneficial effects on total testosterone, SHBG, FAI, serum hs-CRP and plasma TAC levels compared with low-dose vitamin D and placebo groups