Hypercalcemia is a disorder in which the calcium levels in the blood are above normal. Too much calcium in the blood can weaken the bones, cause kidney stones and interfere with the heart and brain functions.
Hypercalcemia most commonly occurs due to overactive parathyroid glands. These four glands are located on or near the thyroid gland. Other causes of hypercalcemia include cancer, certain medications, other health conditions and excessive use of calcium and vitamin D supplements.
Hypercalcemia may be asymptomatic or cause mild to severe symptoms. Treatment for this condition depends on the underlying cause.
Symptoms of more severe hypercalcemia are associated with the affected parts of the body where calcium levels in the blood are high. These may include:
- Kidneys: Excessive calcium in the blood may cause the kidneys to work over time to filter it, which may cause excessive thirst and frequent urination.
- Digestive system: Stomach upset, nausea, vomiting and constipation.
- Bones and muscles: Excessive calcium in the blood often leaks from the bones leading to bone weakness and bone pain. There may also be muscle weakness.
- Brain: Hypercalcemia can interfere with brain function leading to confusion, lethargy and fatigue.
Calcium is essential for the transmission of nerve signals and other functions. If there is insufficient calcium in the blood, the parathyroid glands secrete a hormone. This process stimulates:
- The bones to release calcium into the blood
- The digestive tract to absorb more calcium
- The kidneys to excrete less calcium and activate more vitamin D, which is vital in calcium absorption
Causes of hypercalcemia may include:
- Overactive parathyroid glands (hyperparathyroidism): The most common cause of hypercalcemia, hyperparathyroidism, may result from a small noncancerous tumor on one or more parathyroid glands.
- Cancer: Lung and breast cancer and certain cancers of the blood increase the risk of hypercalcemia. A cancer that has spread to the bones may also lead to hypercalcemia.
- Other medical conditions: Diseases such as tuberculosis and sarcoidosis can raise the levels of vitamin D in the blood, which triggers the digestive tract to absorb more calcium.
- Immobility: Prolonged sitting or lying down may cause hypercalcemia. Bones that do not bear weight release calcium into the blood.
- Medications: Certain medications may increase the release of parathyroid hormone.
- Supplements: Excessive amounts of calcium or vitamin D can raise calcium levels in the blood above normal.
- Dehydration: Less fluid in the blood causes the calcium to become more concentrated.
- Hereditary factors: A rare genetic condition called hypocalciuric hypercalcemia causes an increase of calcium in the blood due to faulty calcium receptors in the body.
People with the highest risk of overactive parathyroid glands are women in their 50s.
Possible complications of hypercalcemia may include:
- Osteoporosis: The disease may develop due to continuous release of calcium from the bones into the blood, which weakens the bones.
- Kidney stones: Too much calcium in the urine can form crystals, which over time combine to form kidney stones.
- Kidney failure: Severe hypercalcemia can damage the kidneys and impair their function.
- Abnormal heart rhythm (arrhythmia): Hypercalcemia can affect the electrical impulses that regulate the heartbeat.
- Nervous system problems: Severe cases of hypercalcemia can cause confusion, dementia and come, which can be fatal.