[Current Topics on Vitamin D. Vitamin D and chronic kidney disease].

CKD-MBD is a new clinical concept which defines a systemic disorder of mineral and bone metabolism as a result of CKD. Although various mineral metabolic factors are involved in its pathogenesis, alteration in vitamin D metabolism plays a crucial role among them. Vitamin D receptor activators (VDRAs), which are traditionally considered a cardinal treatment of secondary hyperparathyroidism, have attracted lots of attention for their potential pleiotropic effects through the activation of the vitamin D receptor expressed in multiple organs. In recent years, the deficiency of vitamin D in CKD patients also has received growing interest. The serum 25 (OH) D levels are considered as a useful prognostic marker, and the significances of nutritional vitamin D supplementation are reviewed from a new perspective.