Hypercalcemia is the clinical term for abnormally high calcium levels in the blood. A mineral, calcium plays a role in building bone and is involved in muscle contraction, nerve conduction, and regulation of heartbeat. The body carefully regulates how much calcium gets stored in bone (which constitutes 99 percent of calcium in the body), and how much remains in the blood for these vital functions.
Blood levels of calcium are primarily regulated by parathyroid hormone (PTH), which is secreted by the parathyroid gland. When blood levels of calcium fall—either due to low intake of calcium from the diet, decreased absorption of calcium in the intestine, or insufficient amounts of vitamin D—the parathyroid gland produces more parathyroid hormone. This promotes the release of calcium from bones and the retention of calcium by the kidneys, which leads to increased levels of blood calcium.
The most common cause of hypercalcemia is hyperparathyroidism—a disorder marked by overactivity of one or more of the parathyroid glands, which results in the overproduction of PTH, and, therefore, abnormally high levels of calcium in the blood. Other disorders, especially certain types of cancer, can also cause hypercalcemia.
Severe hypercalcemia can have serious consequences, including kidney damage, dementia, and coma. Treating the underlying disorder is often sufficient to restore blood levels of calcium to normal. However, some of the problems associated with severe hypercalcemia are irreversible.
What Causes Hypercalcemia?
- Most cases are caused by hyperparathyroidism.
- Metastatic bone tumors—tumors that spread to the bone from a primary cancer site—destroy bone tissue and release calcium into the blood. Multiple myeloma—cancer of the bone marrow—is another cause of hypercalcemia.
- Ovarian, kidney, and lung cancer produce PTH-related hormones (PTHrp), causing similar effects on blood calcium levels as the overproduction of PTH.
- Disorders such as sarcoidosis, tuberculosis, and histoplasmosis may cause hypercalcemia.
- Paget’s disease—a disorder characterized by the overgrowth of bone—may cause hypercalcemia.
- Excessive intake of vitamin A or vitamin D may lead to hypercalcemia.
- Certain medications, such as thiazides may induce hypercalcemia.
- Milk-alkali syndrome—a condition caused by excessive intake of calcium-containing antacids—causes hypercalcemia.
- Familial hypocalciuric hypercalcemia—a form of hypercalcemia that is often asymptomatic—is an inherited condition.
- Prolonged bed rest or immobilization (from quadriplegia, for instance) can lead to hypercalcemia.
Symptoms of Hypercalcemia
- Frequent urination
- Increased thirst
- Feeling tired
- Difficulty thinking clearly
- Abdominal pain
- Loss of appetite or weight loss
- Nausea and/or vomiting
- Increased urination
- Muscle weakness or muscle twitches
- Acute renal failure
- Muscle twitches, dementia, irritability, flank pain, apathy, memory loss
- Bowing of the shoulders, bone pain, fractures due to disease, loss of height
- Fatigue, confusion, depression, mental changes, and possibly coma, resulting from severe hypercalcemia
- Very severe hypercalcemia may result in shock, renal failure, and death
Prevention of Hypercalcemia
- In most cases, hypercalcemia is not preventable.
- Hypercalcemia caused by excessive intake of vitamins can be prevented. Discuss the use of vitamins with your physician.
- Blood and urine tests establish the degree and cause of hypercalcemia.
- Patient history and physical examination help determine the seriousness and potential causes of hypercalcemia.
How to Treat Hypercalcemia
- Blood levels of calcium can often be brought back to normal by treating the underlying cause of the disorder.
- Increased fluid intake is recommended to stimulate the kidneys to excrete more calcium. Those with severe hypercalcemia may need intravenous fluids.
- Medications that slow down the speed at which bone is broken down, such as calcitonin and bisphosphonates, may be prescribed.
- In cases involving vitamin D toxicity, sarcoidosis, and tuberculosis, corticosteroids may be prescribed.
- Hemodialysis—a procedure that involves the removal of impurities in the blood—may be recommended if hypercalcemia is severe and if other treatments have failed.
When to Call a Doctor
You should have regular checkups with your physician if you have hyperparathyroidism, or if you have a family member with hyperparathyroidism or hypercalcemia. Also, see your doctor if you have symptoms of hypercalcemia.
Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference
Simeon Margolis, M.D., Ph.D., Medical Editor
Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50
Updated by Remedy Health Media