Conditions InDepth: Hyperthyroidism

Hyperthyroidism is too much thyroid hormone in the blood. The thyroid gland is in the front of the neck. It makes two hormones that control metabolism, such as:

  • How many calories you burn
  • How warm you feel
  • How much you weigh
  • How the body handles things that the heart, gastrointestinal, and nervous system do

The Thyroid Gland

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Graves disease is the most common. It causes the immune system to make antibodies that cause the thyroid gland to make too much hormone.

Hyperthyroidism can also be from:

  • Swelling of the thyroid
  • A nodule on the thyroid
  • Taking too much thyroid replacement
  • Substances made by tumors of the thyroid gland, testes, or ovaries
  • Consuming too much iodine (rare)

Treating hyperthyroidism can lead to hypothyroidism. This is when the gland does not make enough hormone.



Bahn RS, Burch HB, Cooper DS, et al. Hyperthyroidism and other causes of thyrotoxicosis: management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists. Endocr Pract. 2011 May-Jun;17(3):456-520, also published in Thyroid 2011 Jun;21(6):593.
Hyperthyroidism (thyrotoxicosis). Merck Manual Professional Version website. Available at:
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Accessed May 17, 2019.
Hyperthyroidism and other causes of thyrotoxicosis. EBSCO DynaMed website. Available at: https://www.dyname... . Updated November 1, 2018. Accessed May 17, 2019.
Primary hyperthyroidism. National Institute of Diabetes and Digestive and Kidney Diseases website. Available at:
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Updated March 2019. Accessed May 17, 2019.
Thyroid disorders. Healthy Women website—National Women's Health Resource Center website. Available at:
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Accessed May 17, 2019.
Last reviewed March 2019 by EBSCO Medical Review BoardJames P. Cornell, MD
Last Updated: 5/20/2019

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