Michael T. McDermott, MD
McDermott MT. Hyperthyroidism. Ann Intern Med. 2012;157:ITC1-1. doi: 10.7326/0003-4819-157-1-201207030-01001
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Published: Ann Intern Med. 2012;157(1):ITC1-1.
Hyperthyroidism is a clinical state characterized by excessive serum concentrations of thyroxine (T4), triiodothyronine (T3), or both with suppression of serum thyroid-stimulating hormone (TSH) levels. Some observers prefer the term thyrotoxicosis for this condition and restrict the term hyperthyroidism to the types of thyrotoxicosis that are caused when the thyroid gland synthesizes and secretes too much thyroid hormone. To avoid confusion, however, we will consider hyperthyroidism and thyrotoxicosis to be the same and will use only the term hyperthyroidism.
Hyperthyroidism is considered to be "overt" when a low serum TSH level is associated with elevated serum levels of free or total T4 and/or free or total T3. Hyperthyroidism is considered to be "subclinical" when a low serum TSH level is associated with serum T4 and T3 levels that are within the population reference range. Therefore, the terms overt and subclinical are defined biochemically without reference to clinical features. Although symptoms and signs are usually prominent in overt hyperthyroidism, they may or may not be present in subclinical hyperthyroidism. The prevalence of hyperthyroidism in the United States is estimated to be about 0.4%–1.2%, with approximately 40% of cases being overt and 60% being subclinical (1–3).
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Endocrine and Metabolism, Thyroid Disorders.
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Print ISSN: 0003-4819 | Online ISSN: 1539-3704
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