Vitamin D insufficiency does not affect bone mineral density response to raloxifene.

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.