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March 1979


Author Affiliations

La Crosse, Wis

Arch Intern Med. 1979;139(3):377. doi:10.1001/archinte.1979.03630400091035

To the Editor.—  We read with interest the article, "T4-Thyrotoxicosis," by Dorfman and Young in the Archives (138:1016-1017, 1978). In most hyperthyroid patients, the serum concentrations of both thyroxine (T4) and triiodothyronine (T3) are elevated. Hyperthyroidism owing to the hypersecretion of T3 alone ("T3-toxicosis") is a well-established entity and has been suggested to be a premonitory form of hyperthyroidism.1 In addition, serum T3 level is usually elevated to a greater degree, relative to T4 value in conventional hyperthyroidism. For these reasons, some investigators suggest that the serum T3 level is the best test for the diagnosis of hyperthyroidism, and several reviewers state that the serum T3 level is invariably elevated in hyperthyroidism.Dorfman and Young, however, describe a 41-year-old man with well-documented Graves' disease in whom the serum T3 level was persistently normal and the hyperthyroidism was due

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