Association of Vitamin D Status with Serum Androgen Levels in Men

E. Wehr; S. Pilz; B. O. Boehm; W. März; B. Obermayer-Pietsch

Disclosures

Clin Endocrinol. 2010;73(4):243-248. 

In This Article

Abstract and Introduction

Abstract

Objective Studies in rodents indicate a role of vitamin D in male reproduction, but the relationship between vitamin D and androgen levels in men is largely unexplored. We aimed to investigate the association of 25-hydroxyvitamin D [25(OH)D] levels with testosterone, free androgen index (FAI) and SHBG. Moreover, we examined whether androgen levels show a similar seasonal variation to 25(OH)D.
Design In this cross-sectional study, 25(OH)D, testosterone and SHBG levels were assessed by immunoassay in 2299 men who were routinely referred for coronary angiography (1997–2000).
Measurements Main outcome measures were associations of 25(OH)D levels with testosterone, SHBG and FAI. FAI was calculated as testosterone (nmol/l)/SHBG (nmol/l) × 100.
Results Men with sufficient 25(OH)D levels (≥30 μg/l) had significantly higher levels of testosterone and FAI and significantly lower levels of SHBG when compared to 25(OH)D insufficient (20–29·9 μg/l) and 25(OH)D-deficient (<20 μg/l) men (P < 0·05 for all). In linear regression analyses adjusted for possible confounders, we found significant associations of 25(OH)D levels with testosterone, FAI and SHBG levels (P < 0·05 for all). 25(OH)D, testosterone and FAI levels followed a similar seasonal pattern with a nadir in March (12·2 μg/l, 15·9 nmol/l and 40·8, respectively) and peak levels in August (23·4 μg/l, 18·7 nmol/l and 49·7, respectively) (P < 0·05 for all).
Conclusion Androgen levels and 25(OH)D levels are associated in men and reveal a concordant seasonal variation. Randomized controlled trials are warranted to evaluate the effect of vitamin D supplementation on androgen levels.

Introduction

Vitamin D status is mainly determined by ultraviolet-B-induced vitamin D production in the skin, while vitamin D intake by nutrition and supplements plays only a minor role.[1] Vitamin D from either source is hydroxylated in the liver to 25-hydroxyvitamin D [25(OH)D], which is used to determine a patient`s vitamin D status. 25(OH)D is further hydroxylated to its active form, 1,25-dihydroxyvitamin D [1,25(OH)2D]. Serum levels of 1,25(OH)2D are mainly determined by renal 1,25(OH)2D production, which is catalysed by 1α-hydroxylase. Extrarenal expression of 1α-hydroxylase has, however, also been observed suggesting local 1,25(OH)2D production in various tissues and organs throughout the body. Biological actions of vitamin D are mediated through the vitamin D receptor (VDR), which regulates about 3% of the human genome.[2] The VDR is almost ubiquitously expressed in human cells, which underlines the clinical significance of the vitamin D endocrine system.[1,3] Currently, there is great interest in vitamin D because poor vitamin D status is common and has been associated with an increased risk of various chronic diseases including cancer,[4] diabetes,[5] hypertension,[6] autoimmune diseases, musculoskeletal diseases[1] and cardiovascular diseases[1,4,7] as well as all-cause mortality.[8]

Data on the association of vitamin D and gonadal function are sparse but VDR expression has been observed in reproductive tissues such as ovary, uterus, prostate, testis and human sperm.[9–11] VDR knockout mice have significant gonadal insufficiency, decreased sperm count and motility, and histological abnormalities of testis.[3] Moreover, there is a distinct seasonal variation in testosterone levels,[12] which appears to resemble the seasonal variation of 25(OH)D levels, which is a consequence of seasonal differences in sunlight-induced vitamin D production in the skin. The association between vitamin D status and androgens has, however, not been studied in greater detail. Thus, it remains unclear whether there are similar seasonal distributions of 25(OH)D and androgen levels within a given study population.

Hence, the aim of this study was to investigate the association of 25(OH)D levels with testosterone, SHBG and free androgen index (FAI) and to examine the seasonal variation of 25(OH)D, testosterone, FAI and SHBG levels.

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