Calcium Homeostasis: Vitamin D
The role of vitamin D is important in maintaining calcium homeostasis.
Skin
Ultraviolet (UV) light converts 7-dehydrocholesterol in the skin to cholecalciferol (vitamin D3) or pre-vitamin D is directly ingested.
Liver
Cholecalciferol is converted to 25-hydroxyvitamin D (calcidiol) in the liver.
Kidney
25-hydroxyvitamin D is converted to the active metabolite 1,25-dihydroxyvitamin D in the kidney.
PTH
Parathormone (PTH) stimulates resorption of Ca2+ and PO4.