Abstract
PurposeIt has been hypothesized that vitamin D is associated with androgen levels in men. We, therefore, aimed to evaluate whether vitamin D supplementation increases serum total testosterone (TT) levels in men with low TT levels at baseline.MethodsThe Graz Vitamin D&TT-RCT is a single-center, double-blind, randomized placebo-controlled trial conducted between March 2013 and November 2017 at the endocrine outpatient clinic at the Medical University of Graz, Austria. One-hundred healthy men with serum TT levels < 10.4 nmol/l and 25-hydroxyvitamin D [25(OH)D] levels < 75 nmol/l participated in the trial. Subjects were randomized to receive 20,000 IU of vitamin D3/week (n = 50) or placebo (n = 50) for 12 weeks. Primary outcome was TT measured using mass spectrometry. Secondary outcomes were free testosterone, free androgen index, sex hormone-binding globulin, estradiol, follicle-stimulating hormone, luteinizing hormone, metabolic characteristics, and body composition.ResultsNinety-four men [mean age and 25(OH)D: 47 (± 12) years and 56.3 (± 18.3) nmol/l, respectively] completed the study. We found no significant treatment effect on serum TT or on the remaining secondary outcome variables.ConclusionVitamin D treatment had no effect on serum TT levels in middle-aged healthy men with low TT levels.
Highlights
Vitamin D is well known for its role in maintaining calcium homeostasis and promoting bone mineralization [1]
We present results from men with low serum TT levels who participated in the Graz Vitamin D&TT-randomized controlled trials (RCTs) but required longer recruitment time compared to men with normal serum TT concentrations resulting in two separate publications
We present the results of the second arm of the Graz Vitamin D&TT-RCT, a single-center, double-blind, placebo-controlled, parallelgroup study performed at the Medical University of Graz, Austria
Summary
Vitamin D is well known for its role in maintaining calcium homeostasis and promoting bone mineralization [1]. Testosterone is produced in the Leydig cells following pituitary pulsatile LH secretion. Its production is modulated by paracrine and autocrine signals supplied by growth factors and cytokines secreted within the testis [12, 13]. The. European Journal of Nutrition (2019) 58:3135–3146 vitamin D receptor (VDR) is almost ubiquitously expressed in human cells, which underlines the clinical significance of the vitamin D endocrine system [1, 2, 14]. VDR- and vitamin D-metabolizing enzymes are concomitantly expressed in the entire reproductive male tract, including Leydig cells [15]. Vitamin D significantly increased testosterone production in a human primary testicular cell culture model [11]. Vitamin D might be involved in the production of male reproductive hormones
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