THE INFLUENCE OF SINGLE DOSES OF PROPYLTHIOURACIL ON THE KINETICS OF IODINE ACCUMULATION BY THE THYROID GLANDS OF NORMAL AND HYPERTHYROID SUBJECTS*

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Abstract
DURING the past decade, broad clinical experience has amply confirmed the efficacy of drugs of the thiouracil series in the amelioration of thyrotoxicosis (1–6). Studies in animals and man have revealed that agents of this chemical configuration do not inhibit the ability of the gland to concentrate inorganic iodide, but do interfere with the ability of the gland to synthesize hormone from its inorganic substrate (7–11). Throughout this period, it has not been possible directly to quantify the effect of these agents on thyroidal function, since the protein-binding rate, which they affect, could not be measured. A new method has made possible measurement of the rate of organification of thyroidal iodide (12). This method has been employed in studying quantitatively the inhibition of protein-binding of thyroidal iodide produced in 18 patients by varying doses of propylthiouracil. MATERIAL AND METHODS Euthyroid and hyperthyroid individuals, and 2 patients with nontoxic goiter, comprised the 18 subjects. By a method fully described elsewhere (12), measurements of thyroidal organic-binding rate were made, prior to and following the administration of a single oral dose of propylthiouracil. Seven patients received 100 mg., 7 received 50 mg., and 4 received 25 mg. The second test was performed within ten days of the first test, and was begun from one to one and a half hours after the administration of the drug. Data obtained during the second test were corrected for the residual radioactivity in the plasma and thyroid gland, determined prior to the administration of the second dose of I131.