Biology and Mechanisms of Action of the Vitamin D Hormone

The central role of hormonal 1,25-dihydroxyvitamin D-3 [1,25(OH)(2)D-3] is to regulate calcium and phosphorus homeostasis via actions in intestine, kidney, and bone. These and other actions in many cell types not involved in mineral metabolism are mediated by the vitamin D receptor. Recent studies using genome-wide scale techniques have extended fundamental ideas regarding vitamin D-mediated control of gene expression while simultaneously revealing a series of new concepts. This article summarizes the current view of the biological actions of the vitamin D hormone and focuses on new concepts that drive the understanding of the mechanisms through which vitamin D operates.