Hypercalcemia or hypercalcaemia describes a condition in which blood calcium levels are higher than normal. Calcium is an important mineral for the body. 99 percent of the calcium is stored in the bones and about one percent circulates in the blood. Calcium is crucial for bone formation and also for the brain, nerves, and muscles to function properly. When calcium levels are too high or too low (hypocalcaemia), it causes problems in many parts of the body.
Definition & Facts
The word hypercalcemia literally means too much calcium in the blood. There are many possible causes for hypercalcemia, so the diagnosis and treatment, of not just the elevated calcium, but also the underlying conditions can be a critical challenge. 10 to 30 percent of cancer patients will develop hypercalcemia at some point.
About 99 percent of cases of hypercalcemia are caused by parathyroid disease. Left untreated, hypercalcemia can wreak havoc on many organ systems. It can cause osteoporosis, bone fractures and curvature of the vertebral column in the musculoskeletal system.
In the urinary system, it can cause kidney stones and kidney failure. In the cardiovascular system, it can interfere with the electrical impulses that regulate heart beat and cause cardiac arrhythmia. In the central nervous system, it can cause confusion, lethargy, dementia, coma, and even death.
Symptoms & Complaints
Some common symptoms are excessive thirst, dehydration, loss of appetite, and fatigue. Digestive symptoms can include nausea, vomiting, and constipation. Bone pain, abdominal pain, and muscle weakness can also occur.
Confusion and lethargy can also occur and are also indicators of severe hypercalcemia. Heart arrhythmia is another symptom associated with severe hypercalcemia.
The most common cause of hypercalcemia is an overactive parathyroid gland (hyperparathyroidism). The kidneys filter the blood and keep the calcium concentration balanced. Hormones from the parathyroid control the absorption of calcium by the kidneys. When they do no function properly, too much calcium will remain in the blood.
This condition is referred to as primary hyperparathyroidism when the problem originates in the parathyroid as opposed to being a complication of a problem occurring in a different part of the body (secondary hyperparathyroidism). Primary hyperparathyroidism is often caused by a benign tumor on the parathyroid gland or the enlargement of the gland.
The second most likely cause is the spread of cancer. One way that cancer causes hypercalcemia is that when it metastasizes or spreads to the bone, it destroys the bone. When the bone breaks down, it releases the stored calcium back into the bloodstream.
There are several other ways that cancer causes hypercalcemia. Some tumors can produce a protein that mimics the hormone that the parathyroid produces, triggering the release of calcium into the bloodstream. Other cancers interfere with kidney function as does dehydration caused by the nausea and vomiting associated with cancer and chemotherapy.
Heredity can also be a factor. Familial hypocalciuric hypercalcemia is a rare genetic disorder that causes defective calcium-sensing receptors that in turn do not properly regulate the blood calcium levels.
Diagnosis & Tests
An inquiry into the patient's medical history and physical examination are standard components of the diagnostic process. Hypercalcemia can be diagnosed with a routine blood test. The normal range for calcium is 8.7-10.4 mg/dL. Any result over 10.4 mg/dL is considered elevated. A result over 14 mg/dL is considered an acute metabolic emergency.
Once hypercalcemia is determined, further testing is often required to determine the underlying cause. Another blood test will often be run to determine if the parathyroid hormone level is high. If cancer or sarcoidosis is suspected, the doctor will often also order medical imaging of the lungs or bones such as magnetic resonance imaging (MRI) scans and computed tomography (CT) scans.
If other diseases are suspected even further testing will be required for diagnosis. These could include collection of cultures to test for bacterial infections or fungal infections or an inquiry into possible exposure to pathogens.
An interesting note on the diagnosis of hypercalcemia is that when it causes a heart arrhythmia, it makes a distinctive pattern on the EKG electrocardiogram test.
Treatment & Therapy
The treatment for hypercalcemia is often dependent on the severity and the underlying cause. In mild cases, the best option is often to just monitor the bones and kidneys and wait for the body to correct itself. In acute cases, IV fluids can quickly lower the calcium levels.
Several classes of drugs are also often used to treat hypercalcemia. Calcimimetics imitate calcium circulating in the blood and aid in regulating an overactive parathyroid. Biophosphonates can be given intravenously. These help rebuild bone. Calcitonin can help lower calcium levels. Both calcitonin and biophoshonates are also known to have an analgesic effect and can help alleviate bone pain in cancer patients.
The corticosteroid, prednisone is helpful if the hypercalcemia caused by high levels of vitamin D. Dialysis is another treatment that can help when calcium levels are elevated. Dialysis mechanically removes waste from the blood and restores the correct concentration of electrolytes and minerals, including calcium.
When the cause of hypercalcemia is an overactive thyroid gland, surgical removal is also an option. There are four parathyroid glands. A test using a small amount of radioactive material can isolate which gland is not working properly and it can be removed.
Prevention & Prophylaxis
Patients taking medication that is known to elevate calcium levels, and those diagnosed with conditions that cause hypercalcemia can be monitored with routine blood testing. In some instances these patients can be treated before the elevated calcium levels become critical.