The genetics of osteoporosis: vitamin D receptor gene polymorphisms and circulating osteocalcin in healthy Irish adults

Background A relationship between bone turnover and the vitamin D receptor (VDR) genotype is reported in Australian subjects of UK-Irish descent. There is conflicting evidence of linkage between the VDR genotype and differences in bone mineral density. No such study has been carried out on a resident Irish population. Aims This study examined the relationship between serum osteocalcin (a marker of bone turnover) and VDR genotype in Irish adults. Methods One hundred and eighteen healthy Irish adults aged between 19 and 67 were recruited and had two fasting blood samples taken. One sample was analysed for osteocalcin by enzyme immunoassay. The other was used to isolate genomic DNA and determine VDR genotype. Results Tt was the most prevalent VDR genotype (53%) and tt (15%) the least prevalent in this group of healthy Irish adults. The tt VDR genotype was associated with significantly higher levels of serum osteocalcin (29% and 40%) than the Tt or TT VDR genotypes. Conclusions These findings suggest that healthy Irish adults with the tt VDR genotype have higher rates of bone turnover than those with Tt or TT VDR genotypes. They may have a higher risk of low bone mineral density and osteoporosis in later life.