Hypoparathyroidism

What is Hypoparathyroidism?

Definition:
Hypoparthyroidism is having too little parathyroid hormone, which causes abnormal blood levels 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.

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

Hypoparathyroidism is the disease caused by a lack of PTH. Blood calcium levels fall, and phosphorus levels rise. Low blood calcium levels may cause symptoms such as tingling in the lips, fingers, and toes. It may also cause 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 also 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 a total absence of the parathyroid glands at birth. Familial hypoparathyroidism occurs with other endocrine diseases, such as adrenal insufficiency, in a syndrome called type I polyglandular autoimmune syndrome (PGA I).

The risk factors for hypoparathyroidism include recent thyroid or neck surgery, a family history of parathyroid disorder, or certain autoimmune endocrine diseases such as Addison's disease.

Symptoms:

• Tingling lips, hands, and feet
• Muscle cramps
• Pain in the 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, causing breathing difficulties)
• Convulsions (seizures)

Additional symptoms that may be associated with this disease:

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

Signs and tests:

The disease may give the following test results:

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

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

• Urine calcium
• Ionized calcium in the blood

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

Oral calcium carbonate and vitamin D supplements are usually life-long therapy. Blood levels are measured regularly to make sure that the dose is correct. A high-calcium, low-phosphorous diet is recommended.

In the event of a life-threatening attack of low calcium levels or tetany (prolonged muscle contractions), calcium is administered by intravenous (IV) infusion. Precautions are taken to prevent seizures or larynx spasms. The heart is monitored for abnormal rhythms until the person is stable. When the life-threatening attack has been controlled, treatment continues with medicine taken by mouth.

Support Groups:

Expectations (prognosis):
The probable outcome is good if the diagnosis is made early. However, dental changes, cataracts, and brain calcifications are irreversible.

Complications:

• Tetany can lead to a blocked airway, requiring a tracheostomy.
• Stunted growth, malformed teeth, and slow mental development can occur if hypoparathyroidism develops in childhood.
• Overtreatment with vitamin D and calcium can cause hypercalcemia (high blood calcium) and sometimes interfere with kidney function.
• There is an 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 any symptoms of hypoparathyroidism develop.

Emergency symptoms include seizures and difficulty breathing.

Prevention:
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.