1,25-dihydroxyvitamin D3: a kidney-produced steroid hormone essential to calcium homeostasis

Principal among the many relationships involving the metabolism and function of vitamin D is the central role of the kidney in the production of the biologically active steroid, 1,25-dihydroxychole-calciferol. Three important topics under intensive investigation in many laboratories are (1) the role of the kidney as an endocrine organ producing the biologically active form of vitamin D, (2) the regulation of the endocrine organ and its integration in the process of calcium homeostasis, and (3) reevaluation of the wide variety of vitamin D-related disease states as they relate to the central role of the kidney in vitamin D action.