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:
June 09, 2015
- 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.
- Longo DL, et al. Harrison's Online. 18th ed. New York, N.Y.: The McGraw-Hill Companies; 2012. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=4. Accessed Jan. 2, 2014.
- Shane E. Clinical manifestations of hypercalcemia. http://www.uptodate.com/home. Accessed Jan. 2, 2014.
- Goldman L, et al. Goldman's Cecil Medicine. 24th ed. Philadelphia, Pa.: Saunders Elsevier; 2012. http://www.clinicalkey.com. Accessed Jan. 2, 2014.
- Nippoldt TB (expert opinion). Mayo Clinic, Rochester, Minn. Jan. 3, 2014.
- Primary hyperparathyroidism. National Endocrine and Metabolic Diseases Information Service. http://endocrine.niddk.nih.gov/pubs/hyper. Accessed Jan. 2, 2014.
- Horwitz MJ. Hypercalcemia of malignancy. http://www.uptodate.com/home. Accessed Jan. 2, 2014.
- Papadakis MA, ed., et al. Current Medical Diagnosis & Treatment 2014. 53rd ed. New York, N.Y.: The McGraw-Hill Companies; 2014. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=1. Accessed Jan. 2, 2014.
- AskMayoExpert. Hypercalcemia. Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2013.
- Shane E, et al. Treatment of hypercalcemia. http://www.uptodate.com/home. Accessed Jan. 2, 2014.
- Osteoporosis overview. NIH Osteoporosis and Related Bone Diseases National Resource Center. http://www.niams.nih.gov/Health_Info/Bone/Osteoporosis/overview.asp. Accessed Jan. 2, 2014.