THE EFFECTIVENESS OF TRIIODOTHYRONINE OR THYROXINE ADMINISTERED ORALLY IN THE TREATMENT OF MYXEDEMA*†

Abstract

Administration of triiodothyronine or thyroxine orally to patients with myxedema affords uniformly effective thyroid hormone therapy. Daily oral dose required to maintain euthyroidism in athyreotic patients is 70-105 [mu]g of l-triiodothyronine, or 150-200 [mu]g of dl-triiodothyronine, or 300 [mu]g of sodium l-thyroxine. Also, dl-triiodothyronine has approximately 50% the calorigenic activity of l-triiodothyronine, suggesting that the d-isomer is inactive by mouth. Level of the serum protein-bound I of athyreotic patients receiving triiodothyronine is subnormal and is not indicative of their metabolic status. The clinical and metabolic properties of triiodothyronine are qualitatively identical with those of thyroxine and desiccated thyroid.