a deficiency of parathyroid hormone that causes abnormal metabolism of calcium and phosphorus.

Causes, incidence, and risk factors

Calcium and phosphorus are important body minerals. They form the mineral component of bones, and they exist as charged particles called ions in the blood and inside cells. A hormone called parathyroid hormone (PTH) regulates the amount of calcium and phosphorus in bone and blood. Four small glands called parathyroid glands make PTH. The parathyroid glands are located behind the thyroid gland in the neck. Hypoparathyroidism is the clinical condition caused by a lack of parathyroid hormone. Calcium levels in the blood fall, and phosphorus levels rise. Low blood calcium levels may cause symptoms such as tingling of the lips, fingers and toes, and muscle cramps, or spasms. The most common cause of hypoparathyroidism is injury to the parathyroid glands during head and neck surgery. Rarely, hypoparathyroidism is a side effect of radioactive iodine treatment for hyperthyroidism. PTH secretion may be impaired when blood levels of the element magnesium are low or when blood pH is too high, a condition called metabolic alkalosis. DiGeorge syndrome is a childhood disease in which hypoparathyroidism occurs due to congenital absence of the parathyroid glands. Familial hypoparathyroidism occurs with other endocrine diseases such as adrenal insufficiency in a syndrome called Type I polyglandular autoimmune syndrome (PGA I). Risk factors for hypoparathyroidism include recent thyroid or neck surgery, family history of parathyroid disorder, or history of certain autoimmune endocrine diseases such as Addison's disease . The incidence is about 4 out of 100,000 people.

Signs and tests

low

serum calcium level

elevated

serum phosphorus

decreased serum

parathyroid hormone level

decreased

serum magnesium level (possible)

occasionally abnormal heart rhythms on

ECG This disease may also alter the results of the following tests:

calcium; urine

calcium (ionized)

Treatment

The goal of treatment is to restore the calcium and associated mineral balance within the body.

Oral calcium carbonate and Vitamin D supplements are usually life-long therapy. Blood levels require periodic monitoring to ensure proper dosage. A high-calcium, low-phosphorous diet is recommended. Supportive care is necessary for an acute life-threatening attack or hypoparathyroid tetany (prolonged muscle contractions ). Calcium is administered by intravenous infusion. Precautions are taken to prevent seizures or larynx spasms . Heart monitoring for abnormal rhythms is continued until the person is stabilized. When the life-threatening attack has been controlled, treatment continues with oral preparations.

Expectations (prognosis)

The probable outcome is good if the diagnosis is made early. Dental changes, cataracts , and brain calcifications are irreversible changes.

Complications

acute

tetany, which can lead to

respiratory obstruction requiring a tracheostomy

growth retardation, malformation of the teeth, and retarded mental development, which can occur if hypoparathyroidism develops in childhood

over treatment with

Vitamin D and calcium, which can cause hypercalcemia (high blood calcium) and sometimes impaired kidney function

increased risk of

pernicious anemia , Addison's disease , cataract development, and Parkinson's disease

Calling your health care provider

Call your health care provider if symptoms of hypoparathyroidism develop. Emergency symptoms include seizures and difficulty breathing .

Prevention

Close observation after thyroid or neck surgery may alert to early signs of hypoparathyroidism so that treatment with calcium and Vitamin D supplements can be started.