[Effect of vitamin D receptor gene polymorphism on vitamin D therapy for postmenopausal bone loss]

In order to assess the effect of vitamin D receptor (VDR) gene polymorphisms on vitamin D3 therapy for postmenopausal bone loss. Thirty-four Japanese postmenopausal women, administered vitamin D3 (Alfarol 1.0 microgram/day) and Ca (2.0 g/day) for 18 months, were analyzed by RFLP. Bone mineral density (BMD) at the lumbar spine (L2-4) and Os-calcis were measured every 6 months by dual energy X-ray absorptiometry (DXA) and single energy X-ray absorptiometry (SXA). VDR gene allelic polymorphisms were assessed by Bsm 1 endonuclease restriction after specific PCR amplification. Genotypic polymorphism was defined as BB, bb and Bb. The genotypes were BB in 1 (3.1%), Bb in 13 (40.6%), and bb in 18 (56.3%). The women in these two major VDR genotype groups (Bb and bb) were similar in their backgrounds (in terms of age, body mass index, and BMD in premedication), but the VDR genotype was associated with the percent of change in BMD after treatment. In Group-Bb, the mean percent increases in L2-4 BMD were 3.2%, 4.9% and 4.1% at 6, 12 and 18 months. In contrast, in Group-bb they were 0.8%, 1.8% and 1.2% at the same points. Analysis of VDR alleles may prove useful in selecting the vitamin D therapy for osteopenia before treatment.