Relation of serum 25 hydroxyvitamin D levels to bone mineral density in southern Chinese postmenopausal women: A preliminary study

Background objectives: Vitamin D insufficiency is prevalent in postmenopausal women and has been related to low bone mineral density (BMD). However, controversial results have been reported for the relationship between serum 25-hydroxyvitamin D [25(OH)D] levels and BMD. This study was done to investigate whether serum 25(OH)D levels were associated with BMD in postmenopausal women living in Guangzhou in southern China. Methods: This cross-sectional study involved 119 asymptomatic postmenopausal women, aged 48-85 yr, who were consecutively selected from Guangzhou city. BMD was measured at the lumbar spine and femoral neck. The correlation between serum 25(OH)D levels and BMD wes investigated. Results: With increasing serum 25(OH)D levels categorized as < 20, 20-30, and >= 30ng/ml, the PTH levels decreased gradually ( P=0.031). Bivariate correlation analyses showed an inverse relationship between serum 25(OH)D and PTH levels after controlling for age and BMI (r=-0.209, P=0.023). Although subjects with vitamin D < 30 ng/ml had significantly lower BMD, age- and BMI-adjusted serum 25(OH)D was weakly correlated with BMD at femoral neck (r=0.185, P=0.045), and not at lumbar spine (r=0.172, P=0.063). In multiple regression analyses, serum 25(OH)D was a predictor for BMD at femoral neck (R-2=0.424). However, serum beta-CTX was a determinant for BMD at lumbar spine (R-2=0.361). Interpretation conclusions: Serum 25(OH)D levels showed a positive correlation with BMD at femoral neck and serum beta-CTX levels were inversely correlated with BMD at lumbar spine in postmenopausal women. Further studies are needed to elucidate the clinical impact of these findings.