The parathyroid glands regulate the amount of calcium in the bloodstream. People with abnormalities in their parathyroid who have an abnormally high amount of calcium may experience constipation, vomiting, kidney stones and fractures and may also feel weak and tired. A parathyroid disorder that causes a very low level of calcium in the bloodstream can lead to muscle spasms, cramps, abdominal pain and convulsions.
The Parathyroid Gland
Although most people have four parathyroid glands, which are located on the back of the thyroid gland, approximately 22 percent have more than four, and three to five percent have less, according to Geeta Lal, M.D., Assistant Professor of Surgery at the University of Iowa Hospitals and Clinics in "Greenspan's Basic & Clinical Endocrinology." The parathyroid glands are responsible for increasing the amount of calcium in the bloodstream when the level is low, while decreasing the amount of phosphate in the blood.
The Parathyroid Gland and Calcium
When the calcium levels need to increase, the parathyroid gland releases the parathyroid hormone. This hormone works on the bones and the kidneys, as explained in "Ganong's Review of Medical Physiology" by Kim Barrett, Ph.D., Professor in the Department of Medicine at the University of California. It increases the breakdown of bone, which then releases calcium into the bloodstream. The hormone also tells the kidneys to reabsorb calcium, and to increase their formation of the active form of vitamin D, which increases the amount of calcium that the intestines absorb.
Hyperparathyroidism
This describes the condition where one or more of the parathyroid glands are releasing an abnormally high amount of the parathyroid hormone into the bloodstream. It is the main reason for someone to have a high blood calcium level, per James Lewis, III, M.D. of Nephrology Associates in "The Merck Manual for Healthcare Professionals." Most of the time, it is due to a parathyroid adenoma, which is called a benign tumor because it does not spread to other tissues and organs. This tumor releases calcium regardless of the calcium level, and this results in a high amount in the bloodstream.
Hypoparathyroidism
If the parathyroid gland is not releasing enough of the parathyroid hormone, people may develop this disorder. It can be the result of an autoimmune disease which attacks the gland instead of only attacking foreign substances like bacteria or viruses, or it can be the result of a missing parathyroid gland in a newborn who has DiGeorge syndrome. Most of the time, however, it is due to damage from thyroid surgery, writes Dr. Lal in "Schwartz's Principles of Surgery." A damaged or missing gland will lead to a low blood calcium level.
References
- "Ganong's Review of Medical Physiology"; Kim Barrett, Ph.D., Susan Barman, Ph.D. et al.; 2010
- "Greenspan's Basic & Clinical Endocrinology"; David Gardner, M.D., Dolores Shoback, M.D.; 2007
- "Schwartz's Principles of Surgery"; F. Charles Brunicardi, M.D.; 2010
- The Merck Manual for Healthcare Professionals: Disorders of Calcium Concentration
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