Vitamin D supplementation and testosterone concentrations in male human subjects

Abstract

Summary: Objective: A possible association between serum 25‐hydroxyvitamin D and testosterone levels has been reported; however, contradictory results have emerged. Design: To investigate a causal link between vitamin D and testosterone status, we studied the effect of vitamin D supplementation on serum testosterone concentrations in three independent intervention studies including male patients with heart failure (study 1), male nursing home residents (study 2) and male non‐Western immigrants in the Netherlands (study 3). Methods: In study 1, 92 subjects were randomized to either vitamin D (2000 IU cholecalciferol daily) or control. Blood was drawn at baseline, after 3 and 6 weeks. In study 2, 49 vitamin D deficient subjects received either vitamin D (600 IU daily) or placebo. Blood was drawn at baseline, after 8 and 16 weeks. In study 3, 43 vitamin D deficient subjects received either vitamin D (1200 IU daily) or placebo. Blood was drawn at baseline, after 8 and 16 weeks. Serum 25‐hydroxyvitamin D levels were measured using LC‐MS/MS or radioimmunoassay. Testosterone levels were measured using a 2nd generation immunoassay. Results: Serum 25‐hydroxyvitamin D levels significantly increased in all treatment groups (median increase of 27, 30 and 36 nmol/l in studies 1, 2 3, respectively) but not in the control groups. The documented increase in 25‐hydroxyvitamin D levels, however, did not affect mean testosterone concentrations at the end of the study (median increase of 0, 0·5 and 0 nmol/l in studies 1, 2 and 3, respectively). Conclusions: In this post hoc analysis of three small clinical trials of limited duration in men with normal baseline testosterone concentrations, vitamin D supplementation was not associated with an increase in circulating testosterone concentrations.