Vitamin D receptor gene polymorphism predicts height and bone size, rather than bone density in children and young adults

Peak bone mass is considered to be under strong genetic control. We studied the association among anthropometry, bone density and vitamin D receptor (VDR) genotype in an ethnically homogeneous group of 148 Caucasian children and young adults. Bone density was measured by dual energy X-ray absorptiometry (DXA) and VDR genotype was determined by a direct haplotyping procedure of the BsmI, ApaI, and TaqI restriction fragment length polymorphisms. A second DXA measurement was made after approximately 4 years. Results are expressed as age- and sex-adjusted standard deviation scores (SDS). Previously, the collagen IA1 Sp1 polymorphism was studied in this population. We found VDR genotype to be associated with a 0.4 SDS increased height per allele copy of haplotype '3' (P = 0.04) and a 0.4 SDS increased width of the lumbar vertebral body in the haplotype '3' allele carriers (P = 0.05). We observed a trend towards a 0.3 SDS decreased bone mineral apparent density of lumbar spine (BMAD) per copy of haplotype '3' allele (P = 0.10). In contrast, no association with areal bone mineral density (BMD) was observed. In the follow-up analyses, no differences in height or bone gain among the VDR genotypes were demonstrated. By combining the risk alleles of VDR and collagen IA1 Sp1 genotype, an additive genotype effect on height (P = 0.006) and vertebral body width (P = 0.001) was found. In this exploratory study we found VDR genotype to be associated with frame size and BMAD. The VDR genotype effects on stature and bone size seem to neutralize the effect on areal BMD.