• Definition

    Hypercalcemia is too much calcium in the blood.

    Causes, incidence, and risk factors

    Calcium is important to many body functions, including:

    • Bone formation
    • Hormone release
    • Muscle contraction
    • Nerve and brain function

    Parathyroid hormone (PTH) and vitamin D help manage calcium balance in the body. PTH is made by the parathyroid glands -- four small glands located in the neck behind the thyroid gland. Vitamin D is obtained when the skin is exposed to sunlight, and from dietary sources such as:

    • Egg yolks
    • Fish
    • Fortified cereals
    • Fortified dairy products

    Primary hyperparathyroidism is the most common cause of hypercalcemia. It is due to excess PTH release by the parathyroid glands. This excess occurs due to an enlargement of one or more of the parathyroid glands, or a growth (usually not cancer) on one of the glands.

    Other medical conditions can also cause hypercalcemia:

    • Adrenal gland failure
    • Being bedbound (or not being able to move) for a long period of time
    • Calcium excess in the diet (called milk-alkali syndrome, usually due to at least 2,000 milligrams of calcium per day)
    • An inherited condition that affects the body's ability to regulate calcium (familial hypocalciuric hypercalcemia)
    • Hyperthyroidism
    • Kidney failure
    • Medications such as lithium and thiazide diuretics (water pills)
    • Some cancerous tumors (for example, lung cancers, breast cancer)
    • Vitamin D excess (hypervitaminosis D) from diet or inflammatory diseases

    Hypercalcemia affects less than 1 percent of the population. The widespread ability to measure blood calcium since the 1960s has improved detection of the condition, and today most patients with hypercalcemia have no symptoms.

    Women over age 50 are most likely to have hypercalcemia, usually due to primary hyperparathyroidism.