High-dose vitamin D supplementation and measures of insulin sensitivity in polycystic ovary syndrome: A randomized, controlled pilot trial

Objective To determine the effects of high-dose vitamin D on insulin sensitivity in polycystic ovary syndrome (PCOS). Design Randomized, placebo-controlled trial. Setting Academic medical center. Patient(s) Twenty-eight women with PCOS. Intervention(s) Vitamin D3, 12,000 IU, or placebo daily for 12 weeks. Main Outcome Measure(s) The primary outcome was quantitative insulin sensitivity check index. Secondary outcomes included glucose and insulin levels during a 75-g oral glucose tolerance test and blood pressure. Result(s) Twenty-two women completed the study. Compared with placebo, vitamin D significantly increased 25-hydroxyvitamin D (mean [95% confidence interval] in vitamin D group 20.1 [15.7 to 24.5] ng/mL at baseline and 65.7 [52.3 to 79.2] ng/mL at 12 weeks; placebo 22.5 [18.1 to 26.8] ng/mL at baseline and 23.8 [10.4 to 37.2] ng/mL at 12 weeks). There were no significant differences in quantitative insulin sensitivity check index and other measures of insulin sensitivity; however, we observed trends toward lower 2-hour insulin and lower 2-hour glucose. We also observed a protective effect of vitamin D on blood pressure. Conclusion(s) In women with PCOS, insulin sensitivity was unchanged with high-dose vitamin D, but there was a trend toward decreased 2-hour insulin and a protective effect on blood pressure. Clinical Trial Registration Number NCT00907153.