Hypoparathyroidism

Definition

Hypoparathyroidism is a condition in which the body produces too little parathyroid hormone.

Causes

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 occurs when there is too little PTH. Blood calcium levels fall, and phosphorus levels rise.

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, fingers, and toes
• 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 include:

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

Exams and Tests

This disease may produce 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 in the body.

Oral calcium carbonate and vitamin D supplements are usually lifelong 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.

Outlook (Prognosis)

The outcome is likely to be good if the diagnosis is made early. However, changes in the teeth, the development of cataracts, and brain calcifications are irreversible.

Possible 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.

When to Contact a Medical Professional

Call your health care provider if you develop any symptoms of hypoparathyroidism.

Seizures or difficulty breathing are an emergency. Call 911 immediately.

Prevention

If you undergo thyroid or neck surgery, watch for early signs of hypoparathyroidism and inform your health care provider promptly. This will enable treatment with calcium and vitamin D supplements to be started as quickly as possible.