Hypoparathyroidism

Hypoparathyroidism 

Definition

Hypoparathyroidism is the result of a decrease in production of parathyroid hormones by the parathyroid glands located behind the thyroid glands in the neck. The result is a low level of calcium in the blood.

Description

Parathyroid glands consist of four pea-shaped glands located on the back and side of the thyroid gland. The gland produces parathyroid hormone which, along with vitamin D and calcitonin, are important for the regulation of the calcium level in the body. Hypoparathyroidism affects both males and females of all ages.

Causes and symptoms

The accidental removal of the parathyroid glands during neck surgery is the most frequent cause of hypoparathyroidism. Complications of surgery on the parathyroid glands is another common cause of this disorder. There is the possibility of autoimmune genetic disorders causing hypoparathyroidism such as Hashimoto's thyroiditis, pernicious anemia, and Addison's disease. The destruction of the gland by radiation is a rare cause of hypoparathyroidism. Occasionally, the parathyroids are absent at birth causing low calcium levels and possible convulsions in the newborn. Symptoms in the advanced and continuous stages of hypoparathyroidism include splitting of the nails, inadequate tooth development and mental retardation in children, and seizures.

Abnormal low levels of calcium result in irritability of nerves, causing numbness and tingling of the hands and feet, with painful-cramp like muscle spasms known as tetany. Laryngeal spasms may also occur causing respiratory obstruction.

Diagnosis

Diagnostic measures begin with the individual's own observation of symptoms. A thorough medical history and physical examination by a physician is always required for an accurate diagnosis. The general practitioner may refer the individual to an endocrinologist, a medical specialist who studies the function of the parathyroid glands as well as other hormone producing glands. Laboratory studies include blood and urine tests to help determine phosphate and calcium levels. X rays are useful to determine any abnormalities in bone density associated with abnormal calcium levels. These autoimmune disorders may accompany hypoparathyroidism, but are not an actual cause of it.

Treatment

In the event of severe muscle spasms, hospitalization may be warranted for calcium injections. Raising carbon-dioxide levels in the blood, which can decrease muscle spasms, may be achieved in immediate situations by placing a paper bag over the mouth and blowing into it to "reuse" each breath. It is critical to obtain timely periodic laboratory tests to check calcium levels. A high calcium, low-phosphorous diet may be of significance and is directed by the physician or dietitian.

Prognosis

Presently hypoparathyroidism is considered incurable. The disorder requires lifelong replacement therapy to control symptoms. Medical research however, continues to search for a cure.

Prevention

There are no specific preventive measures for hypoparathyroidism. However, careful surgical techniques are critical to reduce the risk of damage to the gland during surgery.

Resources

Organizations

American Medical Association. 515 N. State St., Chicago, IL 60612. (312) 464-5000. http://www.ama-assn.org.

Key terms

Addison's disease — A disease caused by partial or total failure of adrenocortical (relating to, or derived from the adrenal gland) function, which is characterized by a bronze-like pigmentation of the skin and mucous membranes, anemia, weakness, and low blood pressure.

Autoimmunity — A condition by which the body's defense mechanism attacks itself.

Calcitonin — A hormone produced by the thyroid gland in human beings that lowers plasma calcium and phosphate levels without increasing calcium accumulation.

Hashimoto's thyroiditis — The self destruction of the thyroid cells from an autoimmune disorder.

Hormones — A substance produced by one tissue and conveyed by the bloodstream to another to affect physiological activity, such as growth or metabolism.

Pernicious anemia — A severe anemia most often affecting older adults, caused by failure of the stomach to absorb vitamin B12 and characterized by abnormally large red blood cells, gastrointestinal disturbances, and lesions of the spinal cord.

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hypoparathyroidism /hy·po·para·thy·roid·ism/ (-par?ah-thi´roid-izm) greatly reduced function of parathyroid glands, with hypocalcemia that may lead to tetany, hyperphosphatemia with decreased bone resorption, and other symptoms.

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hy·po·par·a·thy·roid·ism (hp-pr-throi-dzm)

n.

A condition due to diminution or absence of the secretion of the parathyroid hormones.

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hypoparathyroidism (hī´pōper´-thī´roidizm),

n a decrease in parathyroid function, usually the result of surgical removal. Symptoms include tetany, irritability, and muscle weakness. The serum calcium is low, the blood phosphorus elevated, the blood magnesium reduced, and the alkaline phosphatase normal.

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hypoparathyroidism

the condition produced by greatly reduced function of the parathyroid glands or by the removal of these bodies. The lack of parathyroid hormone leads to a fall in serum calcium level, which may result in increased neuromuscular excitability and, ultimately, in tetany. There is also a rise in the plasma phosphate level, which results in a decrease in bone resorption and an increased density of bone.

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iatrogenic hypoparathyroidism

usually due to accidental removal of the glands during thyroidectomy.

idiopathic hypoparathyroidism

recorded in dogs due usually to an immune-mediated diffuse lymphocytic parathyroiditis.

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hypoparathyroidism Endocrinology A condition characterized by ↓ PTH and serum Ca2+ Etiology Congenital absence of the parathyroid glands, accidental excision or injury of parathyroid glands during thyroidectomy or other neck surgery; massive regional RT, magnesium deficiency Risk factors Recent thyroid or neck surgery, family Hx of parathyroid disorder, or autoimmune disease–eg, Addison's disease Clinical Tetany. See PTH.