Context: Vitamin D insufficiency and osteoporosis are common and often coexist in postmenopausal women.
Objective: The objective of this study was to test whether the presence of vitamin D insufficiency at the initiation of raloxifene therapy affected the subsequent response of bone mineral density (BMD).
Design, setting, and participants: We studied 7522 postmenopausal participants of the Multiple Outcomes of Raloxifene Evaluation, a placebo-controlled trial of the effects of raloxifene on BMD and fracture.
Intervention: After enrollment, all participants began daily supplements of 500 mg calcium and 400-600 IU cholecalciferol; 1 month later, women were randomly assigned to placebo or raloxifene.
Main outcome measure: Serum levels of vitamin D [25-hydroxy vitamin D (25OHD)] were measured at enrollment, randomization, and 6 months later. We categorized participants' vitamin D status (deficient, insufficient, or sufficient) based on their randomization 25OHD level. We estimated the effects of treatment on BMD within these subgroups using linear regression models.
Results: At enrollment, 3.2% of participants were vitamin D deficient, and 51.8% were insufficient; after 7 months of cholecalciferol supplementation, 0.2% of all participants remained D deficient, and 23.6% remained insufficient. The effects of raloxifene on hip and spine BMD did not vary by vitamin D status at randomization (P = 0.08 and P = 0.7, respectively).
Conclusion: We conclude that vitamin D status at initiation of raloxifene therapy does not affect the subsequent BMD response when coadministered with cholecalciferol and calcium. After 7 months of cholecalciferol therapy, very few women continued to have 25OHD levels in the deficient range; however, 25OHD levels remained suboptimal in nearly one fourth of the cohort. Additional research is needed to determine whether these observations can be generalized to other antiresorptive agents.