Vitamin D is a fat soluble vitamin that increases the absorption of phosphate and calcium in the body. Vitamin D2 and D3 are most important for the human health.
The hydroxylation of cholecalciferol occur in the liver in order to be active vitamin D. The first hydroxylation of cholecalciferol produces 25-hydroxycholecalciferol.
Thus, the answer is liver, 25-hydroxycholecalciferol.
