Vitamin D modulates bmd gain in postmenopausal women treated with strontium ranelate

Vitamin D deficiency is often reported in subjects treated for osteoporosis. Optimal vitamin D repletion was previously shown to maximize the efficacy of anti-resorptive agents. To date no information exists about the role of vitamin D in the modulation of response to strontium ranelate (SrR) in osteoporotic women. The aim of our study was to investigate the effects on BMD obtained with SrR in accordance to change of vitamin D status over time. A retrospective analysis of 108 women receiving SrR for postmenopausal osteoporosis was carried out. Women were treated with SrR (2g/day), with cholecalciferol (25.000 to 50.000 IU, monthly) and calcium carbonate as appropriate. Lumbar spine and femoral neck BMD, bone turn-over markers (serum BGP and ALP, urine OH-PRO), and serum 25(OH)D were measured at baseline and after 18-months. All participants were divided into two groups according to the median variation of 25(OH)D over the observation period. SrR was associated with improvement of BMD at lumbar spine (0.81±0.11 vs. 0.88±0.11 gr/cm2, at baseline and after 18-months, respectively, p<0.0001) and to a less extent at femoral neck (0.62±0.09 vs. 0.63±0.09 gr/cm2, p=0.2). Only subjects with ?25(OH)D>6.14%, reported a significant BMD gain in comparison to baseline (5.2% (0.2-8.3)) (p=0.03). Change of BMD at femoral neck was positively associated to modification of ALP (r=0.28, p=0.01). This association was not maintained when considering only women with ?25(OH)D<6.14% (r=0.28, p=0.09). At a multiple regression analysis, ALP change was the only predictor of femoral neck BMD modification (? 0.13; SE 0.05; p=0.01). In women with postmenopausal osteoporosis, improving vitamin D status was associated to enhancement of BMD response to SrR, in particular at femoral neck.