Holt R, Pedersen JH, Dinsdale E, et al. - Infertile men experienced that their glucose homeostasis and high-density lipoprotein (HDL) cholesterol levels were impacted in a beneficial manner due to receiving supplementation with high-dose vitamin D.

• A higher risk of metabolic syndrome and mortality exists in men with impaired gonadal function, and vitamin D status may be a reversible modulator.

• This is a single-center, double-blinded, randomized clinical trial with 307 infertile men.

• They were randomized (1:1) to a single dose of 300,000 IU cholecalciferol followed by 1,400 IU cholecalciferol + 500 mg of calcium daily (n = 151) or placebo (n = 156) for 150 days.

• At the end of trial, 13% lower fasting serum insulin levels were detected in men receiving vitamin D supplementation vs the placebo-treated group (65 vs 74 pmol/L) and the former group exhibited 19% lower homeostatic model assessment of insulin resistance (2.2 vs 2.7).

• Higher HDL cholesterol levels were seen in men in the vitamin D group (1.38 vs 1.32 mmol/L) than the placebo group.