Figure 1. Vitamin D Metabolism and Actions.
The calciotropic functions of 1,25-(OH)2-D include the physiological regulation of calcium transport and bone mineralization. The synthesis of circulating 1,25-(OH)2-D which mediates these calciotropic actions is tightly regulated. Non-calciotropic actions involve the activation of vitamin D receptors (VDRs) by locally produced 1,25-(OH)2-D in a number of tissues in a paracrine and autocrine fashion.