RESUMEN
Vitamin D supplementation is recommended for women with osteoporosis. In the FOCUS-D trial comparing the combination tablet alendronate plus vitamin D3 5,600 IU (ALN/D) with standard care (SC) prescribed by patients' personal physicians, ALN/D was more effective in improving serum 25(OH)D and bone turnover markers by 6 months and increasing spine and hip bone mineral density (BMD) after 1 year than SC. This post hoc analysis examined the relationship between BMD gain and 25(OH)D in women in SC receiving alendronate (SC/ALN, n = 134, 52% of the SC group) and in the ALN/D group (n = 257). At baseline, participants were of mean age 73 years and 72% were Caucasian, with a mean 25(OH)D of 14.9 ng/mL. In the SC/ALN group, most received vitamin D, although intake of vitamin D varied extensively (51% received <400 µg/day). In this group, end-of-study 25(OH)D correlated positively with mean percent increases from baseline in lumbar spine and femoral neck BMD [Pearson correlation coefficients (95% CI) = 0.23 (0.02-0.41) and 0.24 (0.03-0.41), respectively]. Baseline 25(OH)D correlated with increases in only lumbar spine BMD [Pearson correlation coefficient (95% CI) = 0.22 (0.01-0.40)]. No correlations between mean BMD change and 25(OH)D were seen with ALN/D. In conclusion, in postmenopausal women with osteoporosis and low 25(OH)D receiving alendronate and a wide range of vitamin D doses, the increase in lumbar spine and femoral neck BMD was positively correlated with serum 25(OH)D achieved by the end of the study and, to some extent, with 25(OH)D concentrations at baseline. The degree of success of alendronate therapy for osteoporosis may depend on the vitamin D status of patients.