Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone. Thyroid hormone is made by the thyroid gland which is a butterfly-shaped gland in the front of the neck. It produces the hormones thyroxine (T4) and triiodothyronine (T3), which control metabolism. This affects how many calories you burn, how warm you feel, how much you weigh, and how the bodies handles many other vital functions of the cardiovascular, gastrointestinal, and nervous systems. Hypothyroidism results in a slower metabolism and slower heartbeat.
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The most common form of hypothyroidism is Hashimoto’s thyroiditis. This condition occurs when your immune system produces antibodies that attack the cells of the thyroid gland, resulting in chronic thyroid inflammation and destruction, resulting in the loss of thyroid function. After Hashimoto’s thyroiditis, the other less common causes include hypothyroidism as a result of neck radiation for lymphoma and treatment of hyperthyroidism or thyroid cancer with radioactive iodine or surgery.
Other causes of hypothyroidism include:
- Subacute thyroiditis—This occurs when there is inflammation of the thyroid gland following a viral upper respiratory tract infection.
- Drugs—Drugs used to treat hyperthyroidism, lithium (used to treat certain psychiatric disorders), certain cardiac medicines, and other medicines (tumor necrosis factor, interleukins, alpha interferon) can cause this condition.
- Medical treatments—Treatments include radiation or surgical removal of part of the thyroid gland (called subtotal thyroidectomy) for the treatment of other thyroid diseases.
- Idiopathic thyroid atrophy—The thyroid tissue shrivels up (atrophies) for unknown reasons.
- Iodine deficiency—This occurs when a thyroid gland does not get enough iodine to produce thyroid hormone (this is rare in the United States)
- Iodine excess—Certain foods (such as shellfish) and certain medicines (such as cough medicine) contain large amounts of iodine, which can ultimately block thyroid hormone production. This is also rare.
- Infiltrative illnesses—These include cancers and certain infections.
- Pituitary adenoma—This is a benign tumor of the pituitary gland that can cause a problem signaling the thyroid to make thyroid hormone.
- Postpartum thyroiditis—This condition usually improves without treatment but may persist.
- Chronic thyroiditis—This usually occurs after hyperthyroidism.
About 5% of Americans have hypothyroidism. This condition usually occurs in adults. But, in some cases, children or infants may have hypothyroidism (called cretinism ). Children require treatment as quickly as possible or mental retardation may result.
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