The Behavior of Labeled Thyroglobulin and Labeled Thyroxine in Patients With Myxedema

INITIAL observations on the behavior of radioiodocasein in a patient having myxedema have been previously reported (1,2). We wish to add comparable observations of the metabolic fate of natural iodoprotein, thyroglobulin, and of its essential constituent, thyroxine. Although many studies of this general nature have been made in the past on man and animals (3, 4), the necessary use of pharmacolcgic amounts of calorigenic substances in order to obtain satisfactory determinations of iodine in body fluids has been a deterrent to further investigation. The use of the isotope method circumvents this difficulty, for it permits the use of physiologic amounts of material. Moreover, it is possible to prepare calorigenic material with sufficient radioactivity and biologic potency to enable one to obtain serial analytic data of considerably greater accuracy and sensitivity than heretofore possible, as well as serial observations in vivo. The present paper deals with the behavior of radiothyroglobulin and radiothyroxine in man, with special reference to the metabolic fate of these compounds as suggested by the nature of their excretory products.