Ch 75 drugs affecting calcium levels & bone mineralization: Calcium: an element critical to blood coagulation & functional integrity of bone, nerve, muscle, & heart; 3 factors to regulate calcium: parathyroid hormone, 2) vitamin d, & 3) calcitonin. Calcium in bone: 88%; bone undergoes continuous remodelling where old bone resorbed after new bone is laid down. Osteoclasts: cells that resorb old bone & osteoblasts: cells that deposit new bone. Absorption in small intestine increased by parathyroid hormone & vit d. Excretion in renal which is reduced by pth, vit d, & calcitonin. Parathyroid hormone, vitamin d, & calcitonin maintain calcium levels by adjusting 3 processes: absorption from the intestine, excretion by the kidney, and, resorption or deposition in bone. Plasma calcium preservation takes priority low serum calcium calcium resorbed from bone & transferred to blood even if compromise structural integrity of bone. Calcium regulates pth release from parathyroid glands in neck; suppressed when high.