, Volume 20, Issue 7, pp 1259-1266
Date: 29 Nov 2008

Vitamin D insufficiency does not affect response of bone mineral density to alendronate

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Abstract

Summary

We investigated whether osteoporosis therapy with alendronate in postmenopausal patients is equally effective in patients who are vitamin D insufficient as in those who are vitamin D sufficient. We found that vitamin D insufficiency is common among patients with low bone density but that vitamin D insufficiency did not impair response to alendronate.

Introduction

Treatment of vitamin D deficiency leads to significant improvements in bone mineral density (BMD); however, whether insufficiency affects BMD’s response to bisphosphonate therapy is unknown.

Methods

To determine whether vitamin D insufficiency at initiation of alendronate therapy for low BMD affects treatment efficacy, we used data from 1,000 postmenopausal women randomly selected from the vertebral fracture arm (n = 2,027) of the placebo-controlled Fracture Intervention Trial of alendronate. Participants were randomly assigned to placebo (50%) or alendronate therapy and most (83%) to calcium (500 mg/day) and cholecalciferol (250 IU/day). We measured serum 25-hydroxy vitamin D (25OHD) at enrollment, then categorized baseline vitamin D status according to 25OHD concentration ( ≤ 10 ng/ml = deficient; >10 but ≤ 30 ng/ml = insufficient; >30 ng/ml = sufficient) and used linear regression to compare the effects of alendronate treatment among these categories.

Results and conclusion

At baseline, participants were vitamin D sufficient (14%), insufficient (83%), and deficient (2%). We found that BMD response to therapy at total hip or spine did not vary by vitamin D status at baseline (p for heterogeneity = 0.6). We determined that vitamin D insufficiency is common among participants with low BMD. However, vitamin D status at initiation of therapy does not affect BMD’s response to alendronate, when it is coadministered with cholecalciferol and calcium.

Scholar’s Grant from the National Osteoporosis Foundation (to D.M.A) and National Institutes of Health grant K23 RR020343 (to D.M.A).