Vitamin D Metabolism Mineral Homeostasis Diet 7-DHCC 1,25(O2D 24,25(OHD2D +PTH +PTH a -PTH Vitamin D Metabolism & Mineral Homeostasis Diet D2 D3 24,25 (OH)2D 25-OHD UVL 7-DHCC 1,25 (OH)2D Ca P +PTH -PTH +PTH PTH