This issue of Endocrinology and Metabolism Clinics, guest edited by Drs. J. Chris Gallagher and Daniel Bikle, is devoted to Vitamin D. Articles in this issue include: The Molecular and Cellular Mechanisms of Action of Vitamin D, Worldwide Review of Serum 25OHD Status; RDA Update (7 Years Post IOM); The Use of Vitamin D Metabolites and Analogs in the Treatment of Chronic Kidney Disease; Effect of Vitamin D on Falls and Physical Performance; Vitamin D Effect on BMD and Fractures; Bariatric S...