What are two common causes of hypercalcemia?

Hypercalcemia, which refers to elevated levels of calcium in the blood, can be attributed to various physiological and pathological conditions. Two of the most common causes are hyperparathyroidism and certain cancers.

Hyperparathyroidism occurs when the parathyroid glands, located in the neck, become overactive and secrete excessive amounts of parathyroid hormone (PTH). PTH regulates calcium levels in the body by promoting calcium release from bones, increasing calcium reabsorption in the kidneys, and enhancing intestinal absorption of calcium. When there is too much PTH, calcium levels can rise significantly, leading to hypercalcemia.

Certain cancers can also lead to hypercalcemia through mechanisms like osteolytic metastasis, where cancer spreads to the bone, causing it to release calcium into the bloodstream. Additionally, some tumors may produce parathyroid hormone-related peptide (PTHrP), which mimics PTH and results in increased calcium release from bones.

The other options provided offer causes that do not typically lead to hypercalcemia. For instance, diabetes and dehydration are not directly associated with increased calcium levels, while hypoparathyroidism generally results in low calcium levels due to insufficient PTH. Excessive vitamin D can cause hypercal