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 burnHow warm you feelHow much you weighHow 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 thyroidIngesting 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.
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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.
Last reviewed December 2015 by Kim A. Carmichael, MD
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