THE INFLUENCE OF VARIOUS FACTORS ON THE UPTAKE OF IODINE BY THE THYROID*

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Abstract
THE mechanism of thyroidal concentration of iodide is unknown. A thyroid-iodide/serum-iodide concentration ratio of 25:1 occurs in normal rat thyroid and may increase to 200–300:1 during chronic administration of an antithyroid agent (1). Various factors influence this iodide-concentrating mechanism. The quantity of iodine per 100 grams of thyroid tissue has been demonstrated to have an inverse relationship to the thyroidal iodide-concentrating ability (2), and a high concentration of serum iodide decreases the thyroidserum iodide ratio (1). Hypophysectomy results in a reduction of the concentrating ability, which is restored by thyrotropin (3). This effect of thyrotropin seems to be enhanced by propylthiouracil, but the administration of propylthiouracil alone in the hypophysectomized animal has an inconstant effect on the iodide concentration gradient (4). The thyroid-serum iodide ratio in hypophysectomized animals may be lowered still further by the administration of thyroxine (4). Potassium thiocyanate reduces the thyroidal accumulation of iodide (5). The action of some other monovalent anions (perchlorate, chlorate, hypochlorite, periodate, iodate, biiodate and nitrate) is similar (6).