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.