Endocrine Abstracts

The vitamin D receptor (VDR) polymorphism, BsmI, has previously been associated with the efficacy of raloxifene therapy. The aim of this study was to examine associations between the BsmI and FokI polymorphisms of the VDR gene and bone density and bone turnover response to raloxifene. One hundred osteopenic postmenopausal women (ages 52 to 80 years, mean 64 years) were prescribed raloxifene (60mg/day) and calcium carbonate (500mg/day) for 48 weeks. Bone density at the lumbar spine (LSBMD) and total hip (THBMD) was measured by DXA at baseline and 48 weeks. Urinary N-telopeptides of type I collagen (UNTX), a marker of bone resorption, was measured at baseline and at 48 weeks by autoanalyser (Vitros Eci). Genotyping was performed using an ABI Prism 7200 Sequence Detection System (Taqman). Eighteen women either withdrew from the study or discontinued treatment before the end of the 48-week study period and were not included in this analysis. The mean percentage changes in LSBMD, THBMD and UNTX in the whole group bone were +1.5%, +0.83% and -24% respectively. Women who were homozygous for the f allele had a significantly higher increase in THBMD than those who were F homozygous (+1.66 (0.42) vs +0.39(0.34) P=0.03, % change (SEM)). Women who were homozygous for the b allele had a slightly higher increase in LSBMD than those who were B homozygous. This borderline association was in the opposite direction to that reported previously. There were no other significant differences in BMD or UNTX response to therapy by genotype. We conclude that in this group of postmenopausal women there is a significant difference between the FF and ff VDR genotypes and THBMD response to raloxifene. Unlike a previous report, we saw no significant associations between BsmI genotypes and BMD response. The study was approved by the 'North Sheffield Local Research Ethics Committee'.