<P> Vitamin D from the diet or skin synthesis is biologically inactive ; enzymatic conversion ( hydroxylation ) in the liver and kidney is required for activation . As vitamin D can be synthesized in adequate amounts by most mammals exposed to sufficient sunlight , it is not an essential dietary factor , and so not technically a vitamin . Instead it could be considered a hormone , with activation of the vitamin D pro-hormone resulting in the active form , calcitriol , which then produces effects via a nuclear receptor in multiple locations . Cholecalciferol is converted in the liver to calcifediol ( 25 - hydroxycholecalciferol ) ; ergocalciferol is converted to 25 - hydroxyergocalciferol . These two vitamin D metabolites ( called 25 - hydroxyvitamin D or 25 ( OH ) D ) are measured in serum to determine a person 's vitamin D status . Calcifediol is further hydroxylated by the kidneys to form calcitriol ( also known as 1 , 25 - dihydroxycholecalciferol ) , the biologically active form of vitamin D. Calcitriol circulates as a hormone in the blood , having a major role regulating the concentration of calcium and phosphate , and promoting the healthy growth and remodeling of bone . Calcitriol also has other effects , including some on cell growth , neuromuscular and immune functions , and reduction of inflammation . </P>
<P> Vitamin D from the diet or skin synthesis is biologically inactive ; enzymatic conversion ( hydroxylation ) in the liver and kidney is required for activation . As vitamin D can be synthesized in adequate amounts by most mammals exposed to sufficient sunlight , it is not an essential dietary factor , and so not technically a vitamin . Instead it could be considered a hormone , with activation of the vitamin D pro-hormone resulting in the active form , calcitriol , which then produces effects via a nuclear receptor in multiple locations . Cholecalciferol is converted in the liver to calcifediol ( 25 - hydroxycholecalciferol ) ; ergocalciferol is converted to 25 - hydroxyergocalciferol . These two vitamin D metabolites ( called 25 - hydroxyvitamin D or 25 ( OH ) D ) are measured in serum to determine a person 's vitamin D status . Calcifediol is further hydroxylated by the kidneys to form calcitriol ( also known as 1 , 25 - dihydroxycholecalciferol ) , the biologically active form of vitamin D. Calcitriol circulates as a hormone in the blood , having a major role regulating the concentration of calcium and phosphate , and promoting the healthy growth and remodeling of bone . Calcitriol also has other effects , including some on cell growth , neuromuscular and immune functions , and reduction of inflammation . </P>
the active form of vitamin d also known as a hormone is called
the active form of vitamin d also known as a hormone is called
calcitriol
calcitriol