Vitamin D receptor gene polymorphism in men and its effect on bone density and calcium absorption

Previous studies have suggested that polymorphism of the alleles of the vitamin D receptor (VDR) gene may account for the major part of the heritable component of bone density in women, possibly mediated in part by impaired calcium absorption from the bowel. In view of the increasing importance of osteoporosis in men, we have now investigated the association between common allelic variations in the vitamin D receptor gene, calcium absorption and bone density in men.

Forty-eight men (median age 64, range 27-77) with a wide range of bone density measurements, comprising 20 men with vertebral crush fractures and 28 male control subjects.

Analysis of the VDR gene polymorphism and measurement of fractional radiocalcium absorption and bone mineral density was performed in all subjects.

The distribution of the three genotypes (TT, tt, Tt) was comparable to that reported previously. There was no significant difference in femoral neck bone density Z-scores between the three genotypes (mean +/- SD TT -0.31 +/- 1.19, tt -0.08 +/- 1.28 and Tt -0.37 +/- 1.17). There were also no significant differences in mean femoral neck bone density T-scores or lumbar spine bone density Z or T-scores between the three genotypes. Fractional radiocalcium absorption was 0.59 +/- 0.27 for TT, 0.69 +/- 0.30 for tt and 0.60 +/- 0.30 for Tt, showing no significant difference between the genotypes.

This study shows no association between vitamin D receptor gene polymorphism and bone density or fractional calcium absorption in a group of men with a range of bone density values. We conclude that the vitamin D receptor gene alleles probably account at most for only a small part of the genetic component of bone density in men.