Hypoparathyroidism

A deficiency of parathyroid hormone (PTH), hypoparathyroidism is caused by disease, injury, or congenital malfunction of the parathyroid glands. Because the parathyroid glands primarily regulate calcium balance, hypoparathyroidism causes hypocalcemia, producing neuromuscular symptoms ranging from paresthesia to tetany.

The clinical effects of hypoparathyroidism are usually correctable with replacement therapy. Some complications of long-term hypocalcemia, such as cataracts and basal ganglion calcifications, are irreversible.

Causes

Hypoparathyroidism results from a variety of causes, as listed below:

• Underdeveloped parathyroid glands at birth
• Medical treatment (radiation to thyroid gland, drug treatment, thyroid or parathyroid surgery)
• An underlying medical condition such as cancer, neck trauma, Wilson's disease (high level of copper in tissues), an excess of iron in tissues, low levels of magnesium

Signs and symptoms

The following are the most common symptoms of hypoparathyroidism. However, each individual may experience symptoms differently. Symptoms may include:

• uncontrollable, painful spasms of the face, hands, arms, and feet
• seizures

The symptoms of hypoparathyroidism may resemble other conditions or medical problems. Always consult your physician for a diagnosis.

Diagnosis

The following test results confirm the diagnosis of hypoparathyroidism:

• radioimmunoassay for PTH: decreased PTH concentration
• serum calcium: decreased level
• serum phosphorus: increased level . electrocardiography (ECG): prolonged QT and ST intervals due to hypocalcemia.

The following test helps provoke clinical evidence of hypoparathyroidism: Inflating a blood pressure cuff on the upper arm to between diastolic and systolic blood pressure and maintaining this inflation for 3 minutes elicits Trousseau's sign (carpal spasm).

Treatment

Because calcium absorption from the small intestine requires the presence of vitamin D, treatment includes vitamin D and calcium supplements. Such therapy is usually lifelong, except for the reversible form of the disease. If the patient is unable to tolerate vitamin D because of hepatic or renal problems, calcitriol may be used.

Acute, life-threatening tetany requires immediate I. V. administration of 10% calcium gluconate to raise serum calcium levels. The patient who's awake and able to cooperate can help raise serum calcium levels by breathing into a paper bag and then inhaling his own carbon dioxide; this produces hypoventilation and mild respiratory acidosis.

Sedatives and anticonvulsants may control spasms until calcium levels rise. Chronic tetany requires maintenance therapy with oral calcium and vitamin D supplements.

Prevention

No preventive measures are available for congenital hypoparathyroidism. However, changes in surgical techniques and medical treatment for thyroid and parathyroid disorders are helping to preserve parathyroid glands and reduce the occurrence of acquired hypoparathyroidism.

If you undergo thyroid or neck surgery, watch for early signs of hypoparathyroidism so that treatment with calcium and vitamin D supplements can be started promptly.