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Blake Medical Center
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Conditions InDepth: Hyperthyroidism

Hyperthyroidism is a condition in which the body has too much thyroid hormone in the blood. Thyroid hormone is made by the thyroid gland, 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
  • How the body handles many other vital functions of the cardiovascular, gastrointestinal, and nervous systems. Thyroid hormones directly affect the heart. If you have too much of the thyroid hormones in your blood, it will cause your heart to beat harder and faster.
The Thyroid Gland
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The most common form of hyperthyroidism is Graves disease. Graves disease is an autoimmune disorder. The body's own immune system produces antibodies that stimulate the thyroid gland to overproduce thyroid hormone. Hyperthyroidism can be the result of other conditions, such as:

  • Inflammation of the thyroid (generally goes away on its own over weeks to months)
  • Formation of nodule on the thyroid (the nodule works independently from the rest of the thyroid)
  • Self-administered dose of too much thyroid
  • Ingesting too much iodine (rarely)
  • Substances secreted by tumors of the thyroid gland, testes, or ovaries (which stimulate the thyroid gland)

Treatment of hyperthyroidism can lead to the opposite condition, hypothyroidism. This is a condition in which the thyroid gland produces too little thyroid hormone. It is easier to treat hypothyroidism long-term than hyperthyroidism. Treatment of hypothyroidism involves taking a pill of thyroid hormone.

It is estimated that 20 million Americans have thyroid disorders.

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

Revision Information

  • Hyperthyroidism (thyrotoxicosis). Merck Manual Professional Version website. Available at: http://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/thyroid-disorders/hyperthyroidism. Updated May 2014. Accessed December 11, 2015.

  • Hyperthyroidism and thyrotoxicosis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated September 14, 2015. Accessed December 11, 2015.

  • Kasper DL, Harrison TR. Harrison's Principles of Internal Medicine. 16th ed. New York, NY: McGraw-Hill; 2005.

  • Primary hyperthyroidism. National Institute of Diabetes and Digestive and Kidney Diseases website. Available at: http://www.niddk.nih.gov/health-information/health-topics/endocrine/primary-hyperparathyroidism/Pages/fact-sheet.aspx. Updated August 2012. Accessed December 11, 2015.

  • Thyroid disorders. Healthy Women website. Available at: http://www.healthywomen.org/condition/thyroid-disorders. Updated February 10, 2012. Accessed December 11, 2015.

  • Vaidya B, Pearce SH. Diagnosis and management of thyrotoxicosis. Brit Med J. 2014;349:g5128.