Thyroxin and Triiodothyronine in Excessive Dosage to Euthyroid Humans

The comparative effects of 3,5,3'-l-triiodothyronine andl-thyroxin in myxedema have been carefully evaluated.1These medications have also been given in physiologic dosage to euthyroid humans to evaluate the effect on the thyroid I131uptake and serum protein-bound iodine (PBI).2We have found no information on the comparative effects of "thyrotoxic" dosage of these drugs and the subsequent effect of stopping these medications. In the course of an evaluation of the effects of induced thyrotoxicosis on mental function,3interesting new data were accumulated on this aspect of thyroid hormone effect. Method Subjects. —Eighteen healthy male college students ranging in age from 20 to 30 years—average age, 23 years—were screened by medical history, physical examination, 24-hour I131-uptake test, basal metabolic rate (BMR), serum PBI,4and serum cholesterol5determination to rule out any question of thyroid disease and to make certain that they could withstand the effects of administration of excessive amounts of