Kidneys 1,25(OH)2D +1,25(OH)2D +PTH CT Bone -CT Ca P Homeostasis Parathormone +1,25(OH)2D (PTH) Calcitonin 1,25(OH)2D (CT) Intestine Ca P HomeostasisCa, P Homeostasis +1,25(OH)2D +PTH -CT +1,25(OH)2D -PTH -CT +1,25(OH)2D Bone Intestine Kidneys Parathormone (PTH) Calcitonin (CT) 1,25(OH)2D Ca, P Homeostasis