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Johns Hopkins Symptoms and Remedies

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Hypothryroidism

The thyroid, a butterfly-shaped gland that lies in front of the trachea, produces hormones involved in metabolism and other diverse functions.

What is it?

Hypothyroidism occurs when the thyroid, a gland in the neck that controls body growth and metabolism, produces insufficient amounts of thyroid hormone, thereby slowing all metabolic processes in the body. Symptoms depend on the degree of thyroid deficiency and may develop slowly over many years. (When full-blown symptoms do occur, the condition is known as myxedema.) Although hypothyroidism can occur at any age and in both sexes, it is most common in women over age 50. The disorder can be completely controlled with proper treatment. In rare cases, however, severe untreated hypothyroidism may result in myxedema coma, a life-threatening condition that may be precipitated by illness, sedatives, cold weather, surgery, or injury. Untreated hypothyroidism occurring during infancy results in mental retardation and dwarfism (cretinism).

What Causes It?

  • Hypothyroidism is frequently due to an autoimmune disorder (such as Hashimoto's disease), wherein the body's natural defenses against infection mistakenly attack healthy tissue (in this case, the thyroid).
  • Hypothyroidism may also occur when the pituitary gland, located at the base of the brain, fails to produce sufficient quantities of thyroid-stimulating hormone (TSH), a regulator of the thyroid gland. (Paradoxically, when hypothyroidism is caused by a defect in the thyroid gland itself , the pituitary releases increased quantities of TSH in an attempt to compensate for low levels of thyroid hor mone.)
  • The disorder may occur following surgical removal of the thyroid gland to treat hyperthyroidism or thyroid cancer.
  • Medical treatments for hyperthyroidism may cause hypothyroidism. Radioactive iodine treatment results in permanent hypothyroidism in more than 50 percent of patients; hypothyroidism due to antithyroid drugs persists only for as long as the drugs are taken (see Hyperthyroidism for more information).
  • Certain drugs such as lithium can interfere with thyroid function.
  • In rare cases an insufficient dietary intake of iodine may cause hypothyroidism.
  • Infants may be born with thyroid defects.
  • Risk of hypothyroidism is greater in women over the age of 50.

Prevention

  • There is no known way to prevent hypothyroidism, although diagnostic screening allows for early detection and treatment in those at risk for congenital hypothyroidism.

Diagnosis

  • Patient history and physical examination are needed. Slowed heart and pulse rates, low systolic bloodpressure (the higher number), and low body temperature suggest hypothyroidism.
  • Blood tests are taken to deter mine levels of thyroid hormone and TSH. (Measur ing TSH is the most sensitive test for hypothyroidism due to disease of the thyroid gland. TSH is not accurate when hypothyroidism is caused by disease of the pituitary gland.)

How to Treat It

  • Lifelong hormone replacement therapy with thyroid hormone (thyroxine) is usually necessary. The lowest effective dose is deter mined and then maintained. (In the elderly and those with coronary artery disease, hor mone replacement is started with a small dose and gradually increased. It is controversial whether to initiate such therapy at all in those with slightly elevated TSH but no symptoms.)
  • If a large goiter causes breathing or swallowing difficulty, surgical removal may be required.
  • Hospitalization is necessar y for treatment of myxedema coma. Intravenous thyroid hor mone replacement, as well as steroid therapy, will usually be administered. In addition, oxygen, artificial respiration, fluid replacement, and other intensive care measures may be warranted.

When to Call a Doctor

  • If you experience the symptoms of hypothyroidism, consult a doctor as soon as possible.