Hypercalcemia

DEFINITION

Hypercalcemia is a condition in which the calcium level in your blood is above normal. Too much calcium in your blood can weaken your bones, create kidney stones, and interfere with the way your heart and brain works.

Hypercalcemia most commonly results from overactive parathyroid glands. These four tiny glands are each about the size of a grain of rice and are located on or near the thyroid gland. Other causes of hypercalcemia include cancer, certain other medical disorders, some medications, and excessive use of calcium and vitamin D supplements.

Signs and symptoms of hypercalcemia may range from nonexistent to severe. Treatment depends on the underlying cause.

CAUSES

In addition to building strong bones, calcium is crucial for the transmission of nerve signals and other functions. If there isn’t enough calcium in your blood, your parathyroid glands secrete a hormone that triggers:

• Your bones to release calcium into your blood
• Your digestive tract to absorb more calcium
• Your kidneys to excrete less calcium and activate more vitamin D, which plays a vital role in calcium absorption

This delicate balance between too much and too little calcium in your blood can be disrupted by a variety of factors. Hypercalcemia may be caused by:

• Overactive parathyroid glands. The most common cause of hypercalcemia, overactive parathyroid glands (hyperparathyroidism) may stem from a small noncancerous tumor on one or more of the four parathyroid glands.
• Cancer. Lung cancer and breast cancer, as well as some cancers of the blood, can increase your risk of hypercalcemia. Spread of cancer (metastasis) to your bones also increases your risk of hypercalcemia.
• Other diseases. Certain diseases, such as tuberculosis and sarcoidosis, may raise blood levels of vitamin D, which stimulates your digestive tract to absorb more calcium.
• Immobility. People with cancer or other diseases that cause them to spend a great deal of time sitting or lying down may develop hypercalcemia. Over time, bones that don’t bear weight release calcium into the blood.
• Medications. Certain drugs — such as lithium, which is used to treat bipolar disorder — may increase the release of parathyroid hormone.
• Supplements. Taking excessive amounts of calcium or vitamin D supplements over time can raise calcium levels in your blood above normal.
• Hereditary factors. A rare genetic disorder known as familial hypocalciuric hypercalcemia causes an increase of calcium in your blood because of faulty calcium receptors in your body.
• Dehydration. A common cause of mild or transient hypercalcemia is dehydration, because when there is less fluid in your blood, calcium concentrations rise.

SYMPTOMS

You might not experience any signs or symptoms if your hypercalcemia is mild. More-severe cases produce symptoms related to the parts of your body affected by the high calcium levels in your blood. Examples include:

• Kidneys. Excess calcium in your blood means your kidneys have to work harder to filter it out. This can cause excessive thirst and frequent urination.
• Digestive system. Hypercalcemia can cause stomach upset, nausea, vomiting and constipation.
• Bones and muscles. In most cases, the excess calcium in your blood was leached from your bones, which weakens them. This can cause bone pain. Some people who have hypercalcemia also experience muscle weakness.
• Brain. Hypercalcemia can interfere with the way your brain works, resulting in confusion, lethargy and fatigue.

When to see a doctor

Contact your doctor if you develop signs and symptoms that may indicate hypercalcemia — such as being extremely thirsty, urinating frequently and having abdominal pain.