Vitamin D and Testosterone in Healthy Men: A Randomized Controlled Trial

The Journal of Clinical Endocrinology & Metabolism
Nov 2017
Citations:54
Influential Citations:3
Interventional (Human) Studies
84
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Methods
Single-center, double-blind, randomized, placebo-controlled trial at the Medical University of Graz, Austria; 98 healthy men aged 18–70 completed the study; TT ≥ 10.4 nmol/L and 25(OH)D < 75 nmol/L at screening; randomized 1:1 to vitamin D or placebo.
Intervention
Vitamin D3, 20,000 IU per week, taken orally as oil drops (50 drops weekly) for 12 weeks.
Results
Vitamin D3 supplementation did not increase total testosterone (TT) in healthy men with normal TT. It significantly decreased QUICKI (insulin sensitivity) and showed a trend toward decreased Matsuda index. Estradiol increased and SHBG decreased; other endocrine, metabolic, and body-composition parameters largely unchanged. No safety concerns observed. This indicates no TT benefit from vitamin D3 in this population and suggests a potential adverse effect on insulin sensitivity; further large-scale studies are needed.
Limitations
Single-center study in healthy middle-aged men; results may not generalize to other populations or to hypogonadal or vitamin D-deficient individuals. Participants had relatively high baseline TT and 25(OH)D; effects in deficient individuals remain unknown. Short duration (12 weeks) and weekly dosing; may not capture longer-term or different-dose effects. Insulin sensitivity assessed with surrogate indices (QUICKI, Matsuda) rather than gold-standard clamps. Dietary calcium intake not assessed. One participant with TT <10.4 nmol/L was included by mistake; sensitivity analysis excluding this participant did not change results.

Abstract

Context: Available evidence shows an association of vitamin D with androgen levels in men. However, results from preliminary randomized controlled trials (RCTs) are conflicting. Objective: To evaluate whether vitamin D supplementation increases total...