THE EFFECT OF LEVO-THYROXINE, DEXTRO-THYROXINE AND LEVO-TRI-IODO-THYRONINE ON THE ELECTROCARDIOGRAM IN MYXEDEMA: PRELIMINARY REPORT

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Abstract
The effect of thyroid hormone in myxedema is probably three-fold: (1) pharmacodynamic via adrenergic potentiation; (2) indirect, through increased metabolic body demands, and (3) histologic. Levo-thyroxine frequently produces initial ecg changes before the circulating purified brucella protein (PBI) or basal metabolic rate is normal. It is probable that the ecg should be used as a guide dosage rather than the PBI or basal metabolic rate. Dextro-thyroxine has a definite effect on all these laboratory determinations. Triiodo-thyronine produces similar ecg effects at very low dosage without any increase in the serum protein bound I, and without elevation of BMR. Six examples, 2 with each substance, are given. A myxedematous patient with congestive heart failure and Cheyne-Stokes respiration was successfully treated with triiodo-thyronine.