Process Overview: Involves processes in the skin, liver, and kidneys to produce active vitamin D.
Steps Involved:
1. Skin Reaction:
7-Dehydrocholesterol in the skin is converted into previtamin D3 by UVB radiation, which then isomerizes to vitamin D3 (cholecalciferol).
2. Liver Conversion:
Cholecalciferol is hydroxylated by 25-hydroxylase (CYP2R1) to form 25-hydroxycholecalciferol (calcifediol).
3. Kidney Conversion:
Calcifediol is further hydroxylated by 1α-hydroxylase (CYP27B1) to form the active form, 1,25-dihydroxycholecalciferol (calcitriol).
4. Role of Calcitriol:
Calcitriol regulates calcium and phosphate homeostasis, enhancing their absorption in the intestines and promoting bone health.