VDR genotype and response to etidronate therapy in late postmenopausal women

Twenty-four late postmenopausal women with osteoporosis were studied. The p atients were separated in three subgroups according to the BsmI polymorphis m of the vitamin D receptor (VDR) gene: BE (n = 8), Bb (n = 10) and bb (n = 6). They did not differ in age (mean ages were 66.0 years, 65.9 years and 63.9 years, respectively), years after menopause (18.7 years, 18.1 years an d 18.4 years) or body weight (64.9 kg, 65.3 kg and 63.8 kg), the variables known to be associated with bone mineral density (BMD). The results show th at the response to antiresorptive bisphosphonate therapy in combination wit h calcium supplementation is modified by VDR genotype. The lumbar spine BMD increased significantly faster in the BE and Bb groups (7.3% and 7.0%, res pectively) compared with the bb group (2.5%) during I year of cyclic etidro nate therapy (400 mg/day) and calcium supplementation (1000 mg/day). The bi ochemical marker of bone resorption (urinary hydroxyproline excretion) as w ell as the bone formation marker (serum levels of osteocalcin) decreased du ring the treatment. With respect to VDR genotype, a significantly higher de crease in osteocalcin level was observed in bb as compared with BE subjects . We conclude that the VDR genotype is involved in an individual's response to cyclic etidronate therapy with calcium supplementation.