Abstract
Vitamin D, the “sunshine” vitamin is a conditional vitamin because some people can get sufficient endogenous D by nonenzymatic photochemical conversion of 7-dehydrocholesterol. Most people need supplementation, and ingested D is converted to the active calcitriol (1,25-hydroxy-D) by hydroxylation in liver and then in kidney. Calcitriol acts not as a coenzyme, but instead as a classic hormone, turning on hundreds of genes in various target tissues, with a primary readout in calcium and phosphate uptake and bone metabolism. Calcitriol exerts these actions as a ligand for the intracellular vitamin D receptor, a transcription factor in the superfamily of nuclear hormone receptors.
Publisher
The Royal Society of Chemistry