What are the most common causes of hypercalcemia?

Hypercalcemia, which is an elevated level of calcium in the blood, has several common causes, among which malignancy and hyperparathyroidism are the most significant.

Malignancy can lead to hypercalcemia through two primary mechanisms: osteolytic metastasis, where cancer spreads to bones and causes the release of calcium into the bloodstream, and through paraneoplastic syndromes. In these cases, certain tumors produce substances that mimic parathyroid hormone, leading to increased bone resorption and calcium release.

Hyperparathyroidism is characterized by excessive secretion of parathyroid hormone (PTH), which orchestrates bone remodeling, kidney calcium reabsorption, and intestinal calcium absorption. In primary hyperparathyroidism, often due to a benign adenoma, the result is increased calcium levels in the serum.

Together, these two conditions account for a significant proportion of hypercalcemia cases, particularly in adults, making them more common than the causes associated with other options. Other conditions mentioned, such as liver failure, Addison’s disease, and renal failure, do not typically result in hypercalcemia and may lead to other metabolic derangements instead.