Relation mellem simpel allelisk variation i et tværsnits- og longitudinelt befolkningsstudie: Vitamin D-receptorlocus, knoglemineraldensitet og postmenopausalt knogletab

The aim of this study was to determine whether common allelic variation at the vitamin D receptor locus is related to bone mineral density and postmenopausal bone loss. Five hundred and ninety-nine healthy women aged 27 to 72 and 125 women with low bone mass aged 55-77 were measured once in a cross-sectional design. Furthermore, 136 women aged 45-54 were followed longitudinally for 18 years. The vitamin D receptor genotypes were determined using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism analysis for three different polymorphic restriction sites (BsmI, ApaI and TaqI). Bone mineral density was measured by photon and X-ray absorptiometry. The cross-sectional study showed no significant relationship between vitamin D receptor genotype and bone mineral density. The maximum difference between homozygotes was 1.3%, P = 0.33, N = 723. The low bone mineral density group had virtually the same genotype frequencies as the normal bone mineral density group. The results of the longitudinal study showed that vitamin D receptor genotype was neither related to early postmenopausal bone loss: age 51-53 (total bone loss at the lower forearm: -3.6% [3.6%], mean [standard deviation]), late postmenopausal bone loss: age 63-69 (total bone loss at the hip: -6.2% [8.7%]) nor to long term postmenopausal bone loss: age 51-69 (total bone loss at the lower forearm: -24.5% [11.4%]). Using analysis of variance to test for differences in the rates of bone loss between the vitamin D receptor genotypes, P values ranged from 0.07 to 0.79. We conclude that common allelic variation at the vitamin D receptor locus as defined by the endonucleases ApaI, BsmI and TaqI is neither related to bone mineral density nor to the rate of bone loss in healthy postmenopausal Danish women.