Hypercalcemia is a condition in which the amount of calcium in the blood is higher than normal.
Some cancers and other conditions can affect the body’s ability to maintain a normal calcium level. Hypercalcemia occurs when:
- increased calcium is released from the bones and absorbed into the blood
- the kidneys cannot get rid of excess calcium
Calcium
The body uses calcium to:
- help muscles contract
- form bones and teeth
- clot blood
- make the heart and nervous system function normally
Calcium is mostly stored in the bones, but is also found in some of the body’s cells and the blood. If there is too much calcium in the blood, it is filtered out by the kidneys. Too little calcium in the blood triggers the body to move calcium out of the bones into the bloodstream. Bones can become weak if they lose too much calcium.
The level of calcium in the blood is controlled by 2 hormones:
- parathyroid hormone (PTH)
- PTH is made by the parathyroid glands.
- The parathyroid glands make more or less PTH, depending on blood calcium levels.
- PTH makes the digestive tract absorb more calcium.
- It stimulates the bones to release calcium into the blood.
- PTH acts on the kidneys to resorb calcium so that less calcium is excreted through the urine.
- calcitonin
- Calcitonin is made by the thyroid.
- It slows the breakdown of bone to lower calcium levels in the blood.
- This hormone acts on the kidneys to prompt them to get rid of excess calcium.
Causes
Hypercalcemia may be caused by:
- cancer
- Bone metastases stimulate certain bone cells (osteoclasts) to increase the breakdown of bone, causing an increase in calcium into the bloodstream.
- Some types of cancer secrete substances that cause the digestive tract to absorb calcium into the bloodstream (similar to the action of parathyroid hormone).
- drugs
- Some medicines that get rid of extra fluid (thiazide diuretics) can cause hypercalcemia.
- Certain hormonal therapies used to treat breast cancer may cause a tumour flare reaction (a sudden, temporary worsening of tumour-related symptoms), which can include hypercalcemia.
- Paget’s disease of the bone
- some endocrine diseases
- bed rest or prolonged immobility
- dehydration
Cancers associated with hypercalcemia
Hypercalcemia usually occurs with advanced cancers and the following types of cancer:
- breast – frequently occurs
- lung – frequently occurs
- multiple myeloma
- Hypercalcemia is fairly common at time of diagnosis or disease recurrence.
- leukemia
- lymphoma
- kidney
- some head and neck cancers
- cancer of unknown primary (CUP)
- gastrointestinal
- parathyroid gland
Symptoms
Some people may not have any symptoms of hypercalcemia or the symptoms may resemble those of other illnesses. Symptoms can develop gradually or suddenly and may include:
- nausea
- vomiting
- loss of appetite (anorexia)
- constipation
- fatigue
- muscle weakness
- increased thirst
- frequent and increased urination
- abnormal heart rhythm
- decreased muscle reflexes
- confusion or difficulty thinking clearly or concentrating
- mental or physical sluggishness (lethargy) or coma
- kidney stones
- seizures
- dehydration
Diagnosis
To diagnose hypercalcemia, the doctor will take a history of symptoms, medications and treatments and complete a physical examination.
Tests that help diagnose hypercalcemia include:
Treatment
Treatment of hypercalcemia depends on the blood calcium level. Levels can range from mild to severe. The goals of treatment are to:
- prevent injury – especially if the person becomes confused or their bones are weak and prone to fractures
- correct dehydration
- increase excretion of calcium by the kidneys
- decrease calcium resorption from the bone
- decrease absorption of calcium from the digestive tract
As the underlying cancer responds to therapy, calcium levels may decrease. Faster treatments for hypercalcemia may be needed. These treatments include:
- extra fluids to stimulate the kidneys to get rid of calcium
- fluids given into a vein (intravenously) to treat dehydration and increase excretion of calcium by the kidneys
- medications to stop the breakdown of bone and lower calcium levels:
- bisphosphonates – These drugs prevent reabsorption of calcium from the bone, which reduces bone breakdown and makes it stronger. Bisphosphonates used to treat hypercalcemia include clodronate (Bonefos), pamidronate (Aredia) and zoledronic acid (Zometa, Aclasta).
- calcitonin – This drug slows the release of calcium from the bone. It may be used as an initial treatment because it lowers calcium levels quickly.
- corticosteroids – These drugs block resorption of calcium by the bone. They are sometimes used to treat hypercalcemia associated with cancers that respond to steroids, such as lymphoma or multiple myeloma.
- dialysis – for severe hypercalcemia or if the kidneys fail
- activity and weight-bearing exercises
Doctors also look at the medications (including vitamins) a person may be taking because some can contribute to hypercalcemia or will affect its treatment.
Blood calcium levels are monitored frequently to see if they are going down and the person is responding to treatment.