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

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.

Parathyroid hormone (PTH) regulates the amount of calcium and phosphorus in bone and blood. The four small parathyroid glands located in the neck, behind the thyroid, make PTH.

Hypoparathyroidism is the clinical condition caused by a lack of PTH. Blood calcium levels 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 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.

• Tingling of lips, hands, and feet
• Muscle cramps
• Pain in face, legs, and feet
• Abdominal pain
• Dry hair
• Brittle nails
• Dry, scaly skin
• Cataracts
• Weakened tooth enamel in children
• Muscle spasms called tetany (can lead to spasms of the larynx with breathing difficulties)
• Convulsions or seizures

Additional symptoms that may be associated with this disease:

• Painful menstruation
• Hand or foot spasms
• Decreased consciousness
• Delayed or absent tooth formation

• Low serum calcium level
• Elevated serum phosphorus
• Decreased serum parathyroid hormone level
• Decreased serum magnesium level (possible)
• Abnormal heart rhythms on ECG (possible)

• Urine calcium
• Ionized calcium in the blood

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 (IV)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.

• 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
• Overtreatment with vitamin D and calcium, which can cause hypercalcemia (high blood calcium) and sometimes causes impaired kidney function
• Increased risk of pernicious anemia, Addison's disease, cataract development, and Parkinson's disease

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