Polymorphism of the vitamin D receptor gene and corticosteroid-related osteoporosis

Corticosteroid therapy (CST) is associated with reduced intestinal calcium absorption, bone loss and increased fracture risk. As polymorphisms of the vitamin D receptor (VDR) gene may be associated with bone mineral density ( BMD) and intestinal calcium absorption, we asked whether patients with a gi ven VDR genotype receiving CST may be at increased or decreased risk fur co rticosteroid-related bone loss and osteoporosis. We measured areal BMD (g/c m(2)) by dual-energy X-ray absorptiometry in 193 women (50 premenopausal, 1 43 postmenopausal) and 70 men with rheumatoid arthritis (n = 44), obstructi ve airway diseases (n = 128) and other corticosteroid-treated diseases (n = 91). All patients received a cumulative dose greater than 1.8 g per year o r a minimum of 5 mg daily of prednisolone or equivalent for at least 1 year . VDR alleles were typed by polymerase chain reaction assay based on the po lymorphic BsmI and TaqI restriction sites. BMD in patients was expressed as a Z-score (mean +/- SEM derived from age- and gender-matched controls. BMD was reduced in patients at the lumbar spine (bb, -0.52 +/- 0.12; Bb, -0.47 +/- 0.11; BE, -0.65 +/- 0.18 SD; p < 0.01), femoral neck (bb, -0.46 +/- 0. 10: Bb, -0.34 +/- 0.10; BB, -0.54 +/- 0.14 SD; p < 0.01), Ward's triangle ( bb, -0.34 +/- 0.10; Bb, -0.31 +/- 0.10, BB, -0.45 +/- 0.13 SD; p < 0.01), a nd trochanter (bb, -0.50 +/- 0.10: Bb, -0.30 +/- 0.10; BB, -0.44 +/- 0.14 S D; p < 0.01). However, there was no significant difference in the deficit i n BMD in any of the genotypes, either before or after adjusting for age, se x, body mass index, disease type, age at onset of disease, disease duration , cumulative steroid dosage, smoking status and dietary calcium intake. Sim ilarly, there were no detectable differences between the BsmI genotypes and the rate of bone loss in 79 patients with repented BMD measurements at an interval of 4-48 months. The data suggest that the VDR genotypes may not be a means of identifying patients at greater risk of corticosteroid-related bone loss.