Polymorphism of the gene of vitamin D receptor in postmenopausal women

BACKGROUND: Conflicting results have been reported on the association betwe en restriction fragment length polymorphism at the vitamin D receptor (VDR) gene locus and bone mineral density (BMD). Population differences in envir onmental factors, such as calcium intake and calcidiol levels which have st rong influence in BMD, may alter this association. PATIENTS AND METHODS: We analyzed the BsmI RFLP at the eight introm of the VDR gene in a population sample (n = 204) of postmenopausal Spanish women a ged 50-65 years being seen clinically and studied calcium intake (dietetic questionnaire) and biochemical parameters (PTH and calcidiol), In parallel bone densitometry were measured in lumbar spine and proximal femur. RESULTS: We identified low BMD of the proximal femur in the BB group, This effect was not observed at other body locations. The calcium intake was lee s than 500 mg/day in 60% of the studied population as calcidiol levels were lower than 10 ng/l in 36% of it. The total group population with normal ca lcium intake (> 1,000 mg/day) showed higher BMD (proximal femur and spine) than the group with low calcium intake, this variation not being observed i n group BB alleles. Interestingly, we observed significant differences in B MD proximal femur between genotype groups BB versus Bb + bb when calcidiol levels were < 10 ng/l. Moreover, whithin the BB subgroup, those subjects wi th normal calcidiol levels have higher proximal femur BMD compared with tho se with low calcidiol levels. CONCLUSIONS: our results indicate an effect of the VDR genotype on BMD prox imal femur which is clearly influenced by calcium intake and calcidiol seru m levels.