Hypercalcemia is an excessive amount of calcium in the blood.
Causes, incidence, and risk factors:
Calcium is important in the body. It is an important part of the bone, and it exists as a charged particle called an ion in the blood and inside cells. Calcium is important to many body functions including bone formation, muscle contraction, nerve and brain function, and the release of hormones. Parathyroid hormone (PTH) and vitamin D regulate calcium balance in the body. PTH is produced by the parathyroid glands -- four small glands located in the neck behind the thyroid gland. Vitamin D is obtained from exposure of skin to sunlight, and from dietary sources such as fortified dairy products, egg yolks, fish, and fortified cereals.
Primary hyperparathyroidism is the most common cause of hypercalcemia and is due to excess PTH. The drug lithium, used in treating bipolar disorder, may increase PTH release and cause hypercalcemia. A genetic mutation that affects the body's ability to regulate calcium is seen in familial hypocalciuric hypercalcemia (FHH), a benign (non-cancerous) condition. Blood calcium can also be high despite low levels of PTH, however. Some malignant tumors (for example, lung cancers, breast cancer) produce PTH-related peptide (PTHrP) which increases blood calcium. Excess vitamin D (hypervitaminosis D) from diet or inflammatory diseases can also cause hypercalcemia. Kidney failure, adrenal gland failure, hyperthyroidism, prolonged immobilization, use of a class of diuretics called thiazides, and ingestion of massive amounts of calcium (milk-alkali syndrome) are other potential causes.
Hypercalcemia affects from 0.1 to 1% 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 the age of 50 are most likely to be hypercalcemic, usually due to primary hyperparathyroidism.
Signs and tests:
Treatment is directed at the underlying cause of hypercalcemia whenever possible. In cases of hyperparathyroidism, surgery may be needed to remove the abnormal parathyroid gland and cure the hypercalcemia. When hypercalcemia is mild and caused by primary hyperparathyroidism, patients may be followed closely by their doctor over time. A new medication named cinacalcet has been shown to lower calcium levels in the blood by reducing parathyroid hormone production. Severe hypercalcemia causing symptoms and requiring hospitalization is treated aggressively with the following:
Prognosis depends on the underlying cause of hypercalcemia. Patients with mild hyperparathyroidism or hypercalcemia with a treatable cause (for example, primary hyperparathyroidism, dietary hypervitaminosis D) may not suffer complications from hypercalcemia. Patients with hypercalcemia secondary to conditions such as cancer or granulomatous disease may have a poor prognosis due to the underlying disease itself rather than to the hypercalcemia. The complications of prolonged hypercalcemia are uncommon today.
Calling your health care provider:
Contact your physician or health care provider if you have a family history of hypercalcemia, family history of hyperparathyroidism, or if symptoms of hypercalcemia occur.
Most causes of hypercalcemia cannot be prevented. Women over the age of 50 should see their health care provider regularly and have their blood calcium screened periodically. Hypercalcemia from calcium and vitamin D supplements can be avoided by contacting your health care provider for advice if you are taking supplements without a prescription.
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