Objective: We studied whether vitamin D receptor and estrogen receptor gene polymorphism is associated with the effect of hormone replacement therapy on lumbar-spinal bone mineral density in Japanese women.
Study design: The subjects were 82 Japanese women aged 40 to 64 years (49.7 +/- 0.6 years, mean +/- SEM) who had taken hormone replacement therapy for >1 year. Genomic deoxyribonucleic acid was extracted from blood and analyzed for restriction fragment length polymorphism with the restriction endonucleases Taq I, Apa I, and Fok I for vitamin D receptor and Pvu II and Xba I for estrogen receptor.
Results: The subjects with genotype TT had a significantly higher percentage change in bone mineral density per year than those with the Tt genotype (2.8% +/- 0.6% vs -0.8% +/- 1.4%, P =.019). The serum level of pyridinoline cross-linked carboxy-terminal telopeptide of type I collagen decreased by 13% during 1 year of hormone replacement therapy in subjects with the TT genotype (P =. 001) but did not change in women with the Tt genotype. In multiple regression analysis including age, height (centimeters), weight (kilograms), and polymorphisms of the vitamin D receptor and estrogen receptor genes, only age and Taq I polymorphism of the vitamin D receptor gene were associated independently with change in bone mineral density (P =.001 and.004, respectively).
Conclusion: Taq I polymorphism of the vitamin D receptor gene is associated with the effect of hormone replacement therapy on lumbar-spinal bone mineral density and bone resorption markers in Japanese women. Analysis of the vitamin D receptor alleles may prove useful for selection of the optimum therapy for osteoporosis management.