Shim BJ, Lee MH, Lim JY, et al. - In this study, the variation in vitamin D receptor (VDR) expression and cross-sectional area (CSA) in the forearm muscles following vitamin D supplementation was tested in patients with a distal radius fracture (DRF). In this study, 18 women with a median age of 63.5 years who have a DRF were prospectively enrolled. Two biopsies of the forearm muscle were obtained, first at the time of fracture repair and then during hardware removal. During a median interval of 8 months, researchers supplemented 1000 IU of vitamin D per day. They analyzed the variations in VDR expression and CSA by immunohistochemistry. The data exhibited that in patients with a DRF, vitamin D supplementation may increase muscle VDR expression and CSA, particularly in vitamin D-deficient patients. In some patients, the increase in CSA without an increase in VDR expression demonstrates that the impact of vitamin D supplementation on muscle mass could be mediated by the indirect effect of serum vitamin D restoration and by VDR.