noun Pathology.
overactivity of the thyroid gland.
a condition resulting from this, characterized by increased metabolism and exophthalmos.

1895–1900; hyper- + thyroid + -ism

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World English Dictionary
hyperthyroidism (ˌhaɪpəˈθaɪrɔɪˌdɪzəm)
See exophthalmic goitre Also called: thyrotoxicosis overproduction of thyroid hormone by the thyroid gland, causing nervousness, insomnia, sweating, palpitation, and sensitivity to heat
adj, —n

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Medical Dictionary

hyperthyroidism hy·per·thy·roid·ism (hī'pər-thī'roi-dĭz'əm)

  1. Pathologically excessive production of thyroid hormones.

  2. The condition resulting from excessive activity of the thyroid gland, characterized by increased basal metabolism.

hy'per·thy'roid adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
hyperthyroidism   (hī'pər-thī'roi-dĭz'əm)  Pronunciation Key 
An abnormality of the thyroid gland characterized by excessive production of thyroid hormone, which can result in an increased basal metabolic rate, causing weight loss, heart palpitations, and tremors. Compare hypothyroidism.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica


excess hormone production by the thyroid gland.

Learn more about hyperthyroidism with a free trial on Britannica.com.

Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Having a slight tendency to hyperthyroidism in the family helps keep the weight
  down admittedly.
This, accompanied by his bulging eyes and weight loss, suggests hyperthyroidism.
Hyperthyroidism is a condition in which the thyroid gland makes too much
  thyroid hormone.
The purpose of treatment is to reduce pain and inflammation and treat
  hyperthyroidism, if it occurs.
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