INFLUENCE OF IODOALPHIONIC ACID (PRIODAX), WITH AND WITHOUT THYROTROPIN, ON THYROIDAL I131UPTAKE IN EUTHYROID PATIENTS*

Abstract

THE ingestion or administration of iodine-containing solutions is known to suppress thyroidal radioactive iodine uptake in euthyroid individuals. Werner et al. (1) state that a low uptake may persist up to twelve weeks after administration of stable iodine. Keating et al. (2) observed that the ingestion of Priodax (an organic iodine-containing compound used in cholecystography) resulted in low thyroidal radioiodine accumulation for periods ranging from a few weeks to many months. Drummy (3) reported reduction of the radioiodine uptake to less than 15 per cent for at least six months in a majority of 29 euthyroid patients after the ingestion of Priodax. Our experience in the Isotope Clinic at Letterman Army Hospital suggested that the inhibiting effect of Priodax is of shorter duration. Many patients who undergo thyroid function studies have had recent cholecystography with Priodax. Because of this, we felt it important to attempt a more accurate determination of the length of the period during which thyroidal I¹³¹ uptake is diminished after the ingestion of this compound.