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November 18, 1974

Risk Factors in Thyroid Replacement Treatment

Author Affiliations

Redding, Calif

JAMA. 1974;230(7):964. doi:10.1001/jama.1974.03240070016014

To the Editor.—  Within the past two years I have recognized, in a general medical practice not weighted to cardiology, ten women with recurrent supraventricular tachycardia apparently due to conventional doses of replacement or supplemental thyroid hormone. This pattern of illness is of particular interest because it not only seems common and easily curable but also suggests once more that conventional doses of supplemental thyroid hormone (120 to 240 mg of desiccated thyroid hormone daily or the equivalent in liothyronine sodium or levothyroxine sodium) are hazardous, usually creating an iatrogenic hyperthyroid state that is mild enough to maintain "within normal limits" the laboratory tests most frequently used to judge the adequacy of supplemental thyroid, but intense enough to almost universally weaken bone in postmenopausal women1 as well as to affect heart rhythm.Thyrotoxicosis is recognized as a cause of recurrent tachycardia. The ten women reported here were all consuming