Hypercalcemia, or excess calcium levels in the blood, rarely occurs as a result of high dietary calcium intake. Taking too high a dose of calcium supplements or vitamin D can lead to hypercalcemia in some cases, as can a number of diseases and cancers. Hypercalcemia can cause kidney problems, including development of kidney stones. The two most common causes of hypercalcemia, hyperparathyroidism and cancer, account for 90 percent of cases.
Hyperparathyroidism
Primary hyperparathyroidism is the main cause of hypercalcemia. The four parathyroid glands found near or attached to the thyroid gland release parathyroid hormone, which controls calcium, vitamin D and phosphorus levels. Swelling in one of the glands causes excess activity in the gland, which results in excess calcium removal from bones and higher absorption of calcium from the intestines and kidneys. Hyperparathyroidism occurs three times more often in women than men and usually affects people over age 60, according to the Cleveland Clinic. Bone symptoms include bone pain, increased risk of fractures and loss of height. Kidney symptoms include increased urination and kidney stones. Appetite loss, muscle pain, mental confusion and abdominal pain can also occur. In severe cases, removing the gland will reduce calcium levels.
Cancer
Between 10 and 20 percent of people with cancer develop hypercalcemia, the National Cancer Institute says. Cancers most likely to cause hypercalcemia include breast, lung and blood cancers such as multiple myeloma. In 80 percent of cases associated with cancer, cancer cell production of substances that increase calcium absorption from the bones into the bloodstream causes hypercalcemia. Poor kidney function, immobility and gastrointestinal symptoms such as nausea and vomiting in cancer patients can also cause hypercalcemia.
Granulomatous Diseases
Sarcoidosis and other diseases associated with granuloma formation can cause hypercalcemia. Inflammation causes tissue injury that leads to granuloma formation in sarcoidosis and diseases such as tuberculosis, Hodgkin's lymphoma and non-Hodgkin's lymphoma, Wegener's granulomatosis and Crohn's disease. Granulomas increase vitamin D levels in the blood, which in turn increase calcium absorption because vitamin D plays a large role in calcium absorption in the intestine. Limiting vitamin D, calcium intake and sun exposure, which increases vitamin D production through the skin, help reduce calcium levels.
Supplements
Overdosing on vitamin D or calcium supplements can lead to hypercalcemia. High levels of vitamin D will cause excess calcium absorption. Use of topical vitamin D for dermatologic disorders can also raise vitamin D levels over prolonged amounts of time. High doses of calcium carbonate in over-the-counter antacids in amounts usually between 6,000 and 15,000 mg per day can cause a form of hypercalcemia called milk-alkali syndrome, which can lead to kidney failure.
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