ESPE Abstracts

Newer studies have indicated that vitamin D has more widespread effects than the classical effects on bone and calcium-phosphate homeostasis. The presence of the vitamin D receptor (VDR) in the testis and male reproductive tract indicates a role for vitamin D in male reproduction. Indeed, vitamin D deficiency and global knock out models of VDR or CYP27B1 in rodents have shown that vitamin D and calcium are important regulators of male reproductive function. Several groups have in recent years published human data, which is in line with a beneficial role for sperm motility and sex steroid production. However, the clinical importance of vitamin D and calcium in regulating male fertility remains to be explored. To determine the impact of vitamin D and calcium supplementation on male reproductive function Copenhagen Bone Gonadal study (CBG-Study) was conducted. The CBG-study is a single center, double blinded randomized clinical trial of 330 vitamin D insufficient (≤ 50 nmol/l) infertile men. The primary endpoint is changes in semen after 5 months supplementation with 300.000 IE cholecalciferol day one in addition to 1400 IE + 500 mg calcium or placebo once daily. At end of trial, men receiving vitamin D supplementation had no net change in semen quality or pregnancy rate. However, men with vitamin D deficiency had an increase in serum inhibin B and men with low sperm counts had higher pregnancy rates. Moreover, men treated with vitamin D had 13% lower fasting serum insulin concentrations and 19% lower HOMA-IR compared with the placebo-treated men. In conclusion activation of the vitamin D receptor seems to be important for male reproductive function but high-dose vitamin D supplementation had no significant effect on reproductive function except in men with severe vitamin D deficiency although minor beneficial effects on glucose homeostasis and HDL cholesterol levels were found in all infertile men.