Hypoparathyroidism

In medicine(endocrinology), hypoparathyroidism is decreased function of the parathyroid glands, leading to decreased levels of parathyroid hormone(PTH). The consequence, hypocalcemia, is a serious medical condition.

Signs, symptoms and diagnosis

Hypocalcemiais the only real result of parathyroid dysfunction and low PTH levels. This presents with tremor, tetanyand, eventually, convulsions.

In contrast to hyperparathyroidism(hyperfunction of the parathyroids), hypoparathyroidism does not have consequences for bone.

Diagnosis is by measurement of calcium, albumin(for correction) and PTH in blood. PTH degrades rapidly at ambient temperatures and the blood sample therefore has to be transported to the laboratory on ice.

If necessary, measuring cAMP(cyclic AMP) in the urine after an intravenous dose of PTH can help in the distinction between hypoparathyroidism and other causes.

Differential diagnoses are:

• Pseudo-hypoparathyroidism (normal PTH levels but tissue insensitivity to the hormone, associated with mental retardationand skeletal deformities) and pseudo-pseudo-hypoparathroidism (sic).
• Deficiency of Vitamin D or hereditary insensitivity to this vitamin (X-linked dominant).
• Malabsorption
• Kidney disease
• Medication: steroids, diuretics, some antiepileptics.

Causes

Hypoparathyroidism can have a number of divergent causes:

• Removal of the parathyroid glands in thyroidsurgery (thyroidectomy) is a recognised cause. It is now uncommon, as surgeonsgenerally spare them during the procedure after identifying them.
• Autoimmuneinvasion and destruction is the most common non-surgical cause. It can occur as part of autoimmune polyendocrine syndromes(see there).
• Hemochromatosiscan lead to iron accumulation and consequent dysfunction of a number of endocrine organs, including the parathyroids.
• Absence or dysfunction of the parathyroid glands is one of the components of chromosome 22q11 microdeletion syndrome(other names: DiGeorge syndrome, Schprintzen syndrome, velocardiofacial syndrome).
• Magnesiumdeficiency
• Some very rare diseases
• Idiopathic (of unknown cause), occasionally familial

Treatment

Severe hypocalcemia, a potentially life-threatening condition, is treated as soon as possible with intravenouscalcium(e.g. as calcium gluconate). Generally, a central venous catheter is recommended, as the calcium can irritate peripheral veinsand cause phlebitis.

Long-term treatment of hypoparathyroidism is with calcium and Vitamin D3supplementation (D1 is ineffective in the absence of renal conversion). Teriparatide, a synthetic form of PTH (presently registered for osteoporosis) might become the treatment of choice for PTH supplementation, although further studies are awaited.

See also

• Hyperparathyroidismfr:Hypoparathyroïdie

sv:Hypoparathyreoidism

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Hypoparathyroidism Wikipedia article Hypoparathyroidism.