Serum Testosterone Levels Are Not Modified by Vitamin D Supplementation in Dialysis Patients and Healthy Subjects.

INTRODUCTION Low serum testosterone is related to increased mortality in male dialysis patients. An association of vitamin D status with serum androgen levels with concordant seasonal variation has been described, but it is undecided whether vitamin D supplementation improves testosterone levels. METHODS In a randomized, placebo-controlled, and double-blind manner, we investigated the effects of an oral vitamin D supplementation in healthy subjects and hemodialysis patients on testosterone levels. One hundred three healthy individuals received cholecalciferol 800 IE/day (n = 52) or placebo (n = 51) for 12 weeks. Thirty-three hemodialysis patients received cholecalciferol adapted to their serum levels following current guidelines (n = 15) or placebo (n = 18) for 12 weeks. RESULTS In healthy individuals, 25(OH)D3 levels rose significantly in the verum group (38.1 ± 13.7 vs. 72.5 ± 15.4 nmol/L, p < 0.001), whereas in the placebo group, levels dropped (37.7 ± 14.7 vs. 31.9 ± 13.1, p < 0.001). Testosterone levels did not change significantly (verum, males: 20.9 ± 6.6 vs. 20.5 ± 7.9 nmol/L, p = 0.6; verum, females: 0.9 ± 0.5 vs. 0.92 ± 0.5, p = 0.4; placebo, males: 18.5 ± 10.2 vs. 21.8 ± 16.5, p = 0.07, placebo, females: 1.6 ± 4.2 vs. 1.6 ± 4.9, p = 0.6). In dialysis patients, the mean cholecalciferol level was only 32.3 ± 17.8 nmol/L, with only 2% of the values being within the normal range. Cholecalciferol levels normalized in the verum group (29.4 ± 11.2 vs. 87.8 ± 22.3, p < 0.001), whereas levels dropped further in the placebo group (33.6 ± 16.6 vs. 24.6 ± 8.0 nmol/L, p < 0.001). Testosterone levels did not change significantly (verum, males: 8.0 ± 3.7 vs. 7.8 ± 3.8, p = 0.8; verum, females: 1.3 ± 1.0 vs. 1.2 ± 1.0 nmol/L, p = 0.5; placebo, males: 11.9 ± 5.0 vs. 11.6 ± 4.0 nmol/L, p = 0.6; placebo, females: 0.8 ± 0.5 vs. 0.7 ± 0.4 nmol/L, p = 0.8). CONCLUSION Serum testosterone levels in hemodialysis patients and healthy individuals are independent from vitamin D status and cannot be significantly increased by cholecalciferol supplementation.