Vitamin D status, parathyroid function, bone turnover, and BMD in postmenopausal women with osteoporosis: global perspective.

Poor vitamin D status is common in the elderly and is associated with bone loss and fractures. The aim was to assess worldwide vitamin D status in postmenopausal women with osteoporosis according to latitude and economic status, in relation to parathyroid function, bone turnover markers, and BMD. The study was performed in 7441 postmenopausal women from 29 countries participating in a clinical trial on bazedoxifene (selective estrogen receptor modulator), with BMD T-score at the femoral neck or lumbar spine 75 nM was 5.9%, 29.4%, 43.5%, and 21.2%, respectively, in winter and 3.0%, 22.2%, 47.2%, and 27.5% in summer. Worldwide, a negative correlation between 25(OH)D and latitude was observed. With increasing 25(OH)D categories of <25, 25-50, 50-75, and >75 nM, mean PTH, OC, and CTX were decreasing (p < 0.001), whereas BMD of all sites was increasing (p < 0.001). A threshold in the positive relationship between 25(OH)D and different BMD parameters was visible at a 25(OH)D level of 50 nM. Our study showed a high prevalence of low 25(OH)D in postmenopausal women with osteoporosis worldwide. Along with latitude, affluence seems to be an important factor for serum 25(OH)D level, especially in Europe, where it is strongly correlated with latitude.