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 most common form of hyperthyroidism is
Graves disease. Graves disease is an autoimmune disorder in which the body's own immune system produces antibodies that stimulate the thyroid gland to overproduce thyroid hormone. Hyperthyroidism can also be the result of other conditions, such as:
Inflammation of the thyroid (generally goes away on its own over weeks to months)
Formation of a 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.
Hyperthyroidism (thyrotoxicosis). Merck Manual Professional Version website. Available at: http://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/thyroid-disorders/hyperthyroidism. Updated July 2016. Accessed November 28, 2017.
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 November 28, 2017.
Thyroid disorders. Healthy Women website. Available at: http://www.healthywomen.org/condition/thyroid-disorders. Accessed November 28, 2017.
Vaidya B, Pearce SH. Diagnosis and management of thyrotoxicosis. Brit Med J. 2014;349:g5128.
Last reviewed November 2018 by
EBSCO Medical Review Board
James Cornell, MD
Last Updated: 12/20/2014
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