Effect of Stable Iodine on Thyroid Iodine Release

Abstract

To clarify the mode of action of large doses of stable iodine on the thyroid gland in Graves' disease, experiments have been performed on 3 hyperthyroid patients and 1 euthyroid subject. Two isotopes were administered at different time intervals before iodine (as KI solution) was given. Iodine produced a temporary inhibition of organification of recirculating labeled iodine in all patients. In the 3 toxic patients, there was a decline in circulating hormone concentration beginning within a day after the institution of KI therapy and continuing throughout the period of iodine administration. By following the blood PBI, and by comparing the decay of thyroid isotope content with the urinary isotope excretion curves, it may be concluded that the main action of iodine on the toxic gland is an inhibition of degradation of thyroglobulin.