[Genetic polymorphism of vitamin D receptor and osteoporosis]. / Polimorfismo genético del receptor de la vitamina D y osteoporosis.

BACKGROUND: Genetic factors condition an important part of bone mass. The role of vitamin D receptor polymorphism (VDR) as genetic marker of osteoporosis is a matter of discussion. We have studied the possible influence of VDR on bone remodelling, calciotropic hormones, on the presence of osteoporosis and osteoporotic bone fractures. PATIENTS, CONTROL POPULATION AND METHODS: A case-control study. We have studied a total of 127 postmenopausal Canarian women from Canary Islands, Spain; 66 healthy controls and 61 with the diagnosis of osteoporosis, which was made by clinical, radiological and densitometric criteria. 17 osteoporotic women have had a fracture: Colles, hip or vertebral (spinal deformity index) fracture. VDR were determined by PCR directed to demonstrate the presence (b) or absence (B) of a restriction target for Bsml in intron 7. We analyzed some biochemical markers of bone remodelling: serum levels of alkaline phosphatase, tartrate resistant acid phosphatase and urine ratios of calcium/creatinine and hydroxyproline/creatinine. We also determined calciotropic hormones: parathyroid hormone and calcitonin. Bone mass was measured by DEXA and TC. RESULTS: There were no significant differences in either biochemical bone remodelling markers or in bone mass between the three genotypes: bb, Bb and BB, either in controls or in osteoporotic women with the exception of alkaline phosphatase which had a significative increase compared to control in women with unfavorable alleles distribution (bB and BB). Distribution of genotypes was similar between controls and osteoporotic women, with or without fractures. CONCLUSIONS: In Canarian women, VDR genotype is not associated with changes in biochemical markers of bone remodelling or in bone mass or with the presence of osteoporosis or osteoporotic fractures.