Vitamin D receptor genotype and bone mineral density in Caucasian children with congenital hypothyroidism.

: Recent studies in adults suggest that some of the genetic effects on bone mineral density (BMD) and bone turnover are related to allelic variation in the vitamin D receptor (VDR) genes. It has also been suggested in patients with hyperthyroidism that the VDR genotype might influence the risk of low BMD. We examined allelic influences of the VDR gene on BMD and metabolism in 42 children with congenital hypothyroidism (CH) aged 8.5 +/- 3.4 yr treated from the neonatal period and in whom we have previously demonstrated no detrimental effects to the skeleton of prolonged L-thyroxine therapy. The prevalence of the different VDR BsmI polymorphism in this population was as expected for Caucasian children (Bb heterozygote 52%, bb homozygote 31% and BB homozygote 17%). No relationship was found between VDR genotypes and BMD (SDS), nor between VDR genotypes and serum osteocalcin levels as markers of bone formation. However, urinary D-pyridinoline levels, as markers of bone resorption, were related to VDR genotypes (p<0.04). These data indicate that the VRD genotype does have some effect on bone metabolism in children with CH but the present results give no clear indication of a detrimental effect for any given VDR genotype, at least at the BsmI restriction site, on the bone mineralization of children with CH when adequately treated with thyroxine.