Active form of Vitamin D
(C) Calcitriol # Vitamin D Is Metabolized to the Active Metabolite, Calcitriol, in Liver & Kidney.> Cholecalciferol, either synthesized in the skin or from food, undergoes two hydroxylations to yield the active metabolite, 1,25-dihydroxyvitamin D or calcitriol.> Ergocalciferol from fortified foods undergoes similar hydroxylation to yield calcitriol.> In the liver, cholecalciferol is hydroxylated to form the 25-hydroxy-derivative, calcidiol.> This is released into the circula-tion bound to a vitamin D binding globulin, which is the main storage form of the vitamin.> In the kidney, calcidiol undergoes either 1 -hydroxylation to yield the active metabolite 1,25-dihydroxyvitamin D (calcitriol), or 24-hydroxylation to yield a probably inactive metabolite, 24,25-dihydroxyvitamin D (24-hydroxycaicidiol).> Some tissues, other than those that are involved in calcium homeostasis, take up calcidiol from the circulation and synthesize calcitriol that acts within the cell in which it was synthesized.
Cholecalciferol
Calciferol
Calcitriol
25-hydroxy cholecalciferol
Misc.