This document discusses calcium homeostasis and hypercalcemia. It explains that blood calcium levels are tightly regulated by the parathyroid hormone (PTH), vitamin D, gut, bone and kidneys. The main causes of hypercalcemia are primary hyperparathyroidism, malignancy-related hypercalcemia from bone metastases, and hypervitaminosis D from excessive vitamin D intake or production. The document provides details on the pathophysiology, clinical evaluation and management of hypercalcemia.