Background: Osteoporosis is a common disorder with a strong genetic component. Our aim was to evaluate the correlation of the vitamin D receptor FokI start codon polymorphism to bone mineral density and the occurence of osteoporosis.
Methods: We determined the vitamin D receptor FokI start codon polymorphism using polymerase chain reaction-based restriction analysis in 163 postmenopausal women in Taiwan. The vitamin D receptor gene polymorphism was detected by the restriction enzyme FokI, where the F allele indicated the absence of the cuttable site and the f allele its presence. We then related the genotypes to bone mineral density and the occurence of osteoporosis in these women.
Results: The allelic frequencies for 163 postmenopausal women in Taiwan were 59.2% for F and 40.8% for f in FokI restriction fragment length polymorphisms. The prevalence of each genotype in the study population was: 42.3% FF, 33.7% Ff and 24% ff. The three genotypic groups differed significantly in bone mineral density at the lumbar spine (P = 0.029). Bone mineral density was highest in the Ff group and lowest in the ff group at the lumbar spine and the femoral neck. The FokI vitamin D receptor genotype showed a significant effect on the prevalence of osteoporosis in the subjects at the lumbar spine. That is, women with genotype ff had a 2.8 times greater risk for osteoporosis (P < 0.05), and those with genotype FF had a 0.8 times greater risk than women with genotype Ff.
Conclusion: Our findings indicate that the vitamin D receptor FokI start codon polymorphism is associated with reduced bone mineral density and predisposes women to osteoporosis at the lumbar spine.