Conditions InDepth: Hypothyroidism

Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone. The thyroid gland is a butterfly-shaped gland in the front of the neck. It produces the hormones thyroxine (T4), triiodothyronine (T3), and calcitonin. These hormones control metabolism and regulate calcium balance, thus affecting how many calories you burn, how warm you feel, how much you weigh, and the speed and strength of your heartbeat. Hypothyroidism results in a slower metabolism and slower heartbeat.

The Thyroid Gland

© 2008 Nucleus Medical Art, Inc.

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 the loss of thyroid function. After Hashimoto’s thyroiditis, the other more common causes include hypothyroidism as a result of neck radiation for lymphoma and treatment of hyperthyroidism with radiation or surgery.

Other causes of hypothyroidism include:

  • 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.
  • Subacute thyroiditis—This occurs when there is inflammation of the thyroid gland following a viral upper respiratory tract infection.
  • Medical treatments—Treatments include radiation or surgical removal of part of the thyroid gland (called subtotal thyroidectomy) for the treatment of other thyroid diseases.
  • Drugs—Drugs used to treat hyperthyroidism, lithium (used to treat certain psychiatric disorders), certain cardiac medicines (amiodarone), and others (tumor necrosis factor, interleukins, alpha interferon) can cause this condition.
  • Infiltrative illnesses—These include cancers and infections.
  • Pituitary adenoma—This is a benign tumor of the pituitary gland.
  • Postpartum thyroiditis—This condition usually improves without treatment but may persist.
  • Chronic thyroiditis—This usually occurs after hyperthyroidism.

Hypothyroidism is the most common form of thyroid functional abnormality and is far more common than hyperthyroidism . Over five million Americans have this medical condition. It is 4 times more common in women than men. Studies of large populations have shown that as many as one woman in ten over the age of 65 has evidence of the earliest stages of hypothyroidism. This condition can occur in children or infants ( cretinism ) but is most common in adults. Children require treatment as quickly as possible or mental retardation may result.

What are the risk factors of hypothyroidism?
What are the symptoms of hypothyroidism?
How is hypothyroidism diagnosed?
What are the treatments for hypothyroidism?
Are there screening tests for hypothyroidism?
How can I reduce my risk of hypothyroidism?
What questions should I ask my healthcare provider?
Where can I get more information about hypothyroidism?

References:

American Medical Women’s Association website. Available at: http://www.amwa-doc.org/ .

American Thyroid Association website. Available at: http://www.thyroid.org/ .

Garber JR, Hennessey JV, Liebermann JA 3rd, Morris CM. Clinical update. Managing the challenges of hypothyroidism. J Fam Pract. 2006;55:S1-8.

Harrison’s Principles of Internal Medicine. 15th ed. Mc-Graw-Hill; 2001.



Last reviewed May 2007 by David Juan, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

DiggDeliciousNewsvineRedditStumbleTechnoratiFacebook