Parathyroid Glands Health Article

Common diseases and disorders

• Primary hyperparathyroidism. The most common disease of parathyroid glands is overactivity, meaning that too much PTH is being produced. Hyperparathyroidism is the result of parathyroid gland disease, which then secretes the hormone in abnormally high amounts. Common symptoms of this disorder are chronic increases of calcium amounts in the blood (hypercalcemia), kidney stones, and decalcification of bone. The major symptom of this condition is decalcification of bone, leading to brittle bones that fracture easily (rubber bones).
• Secondary hyperparathyroidism. In this form of hyperparathyroidism, the condition is due to a disease not directly affecting the parathyroid glands that leads to high levels of PTH. Kidney disease is often associated with this disorder because it reduces the renal excretion of phospate, causing increased phosphate levels in the blood which then decrease the level of free ionized calcium. In addition, most of the calcium in extracellular fluid is not in the ionized form. Rather, at least 50% of the extracellular fluid calcium is in the non-ionized form bound to proteins and phosphate. Secondary hyperparathyroidism is also due to a poor diet, deficient in calcium or vitamin D, or which is high in phosphorus (found in meat).
• Hypoparathyroidism. Hypoparathyroidism results from inadequate PTH production. It is a rare condition, most commonly caused by damage or removal of the parathyroid glands at the time of parathyroid or thyroid surgery. Typically, it results in decreased concentrations of calcium and increased concentrations of phosphorus in blood. The resulting hypocalcemia often leads to convulsions, and can be life-threatening.
• Parathyroid adenoma. Parathyroid adenoma commonly occurs on only one of the four parathyroids. The condition accounts for 87–93% of all patients diagnosed with primary hyperparathyroidism. The enlarged parathyroid that has the tumor usually secretes all the PTH with the other three glands responding to the high calcium levels caused by the overactive one by becoming dormant. Parathyroid adenoma is very rarely cancerous (less than one in 500), but it slowly damages the body by causing abnormally high level of calcium in the blood.
• Secondary osteoporosis. This bone disorder results from a slight excess of bone removal over bone formation, often the result of prolonged hyperthyroidism.
• Congenital hypoparathyroidism. Individuals with this condition are born without parathyroid tissues. It is due to a genetic disorder resulting in abnormal genes that either encode for abnormal forms of PTH or its receptor, or prevent normal parathyroid gland development before birth.

BOOKS

Bilezikian, John P., Robert Marcus, and Michael Levine, eds. The Parathyroids, Second edition. New York: Academic Press, 2001.

Whitfield, James F., Paul Morley, and Gordon E. Willick. The Parathyroid Hormone: An Unexpected Bone Builder for Treating Osteoporosis. Georgetown: Landes Bioscience, 1998.

PERIODICALS

Angeletti, R. H., T. D'Amico, and J. Russell, "Regulation of parathyroid secretion. Chromogranins, chemokines, and calcium." Advances in Experimental and Medical Biology 482 (2000): 217–223.

Goltzman, D., and J. H. White, "Developmental and tissue-specific regulation of parathyroid hormone." Critical Reviews in Eukaryotic Gene Expression 10 (2000): 135–49.

Mihai, R., and J. R. Farndon. "Parathyroid disease and calcium metabolism." British Journal of Anaesthesiology 85 (July 2000): 29–43.

Strewler, G. J. "Medical approaches to primary hyperparathyroidism." Endocrinology & Metabolism, Clin. North Am. 29 (September 2000): 523–529.

Weigel, R. J. "Nonoperative management of hyperparathyroidism: present and future." Current Opinions in Oncology 13 (January 2001): 33–38.

Whitfield, J., P. Morley, and G. Willick, "The parathyroid hormone, its fragments and analogues-potent bone-builders for treating osteoporosis." Expert Opinions in Investigative Drugs 9 (June 2000): 1293–1315.

OTHER

"Hyperparathyroidism." Endocrine Disorders and Endocrine Surgery Webpage. <http://www.endocrineweb.com/hyperpara.html>.

Monique Laberge, Ph.D.