Goiters with High Radioiodine Uptake and Other Characteristics of Iodine Deficiency in Rats Chronically Treated with Aminoglutethimide1,2

In experiments with rats, small doses of the antithyroid drug aminoglutethimide (AG), given as a single injection (2 mg) or as an admixture to an iodine-enriched diet for a few days, had a propylthiouracil-like action on thyroidal radioiodine metabolism characterized by a decrease of uptake, organic binding, release of labeled PBI and synthesis of iodothyronines. However, chronic administration of AG for more than 3 weeks produced small goiters characterized by an increase of radioiodine uptake and organic binding and an accelerated release of labeled PBI, while iodothyronine synthesis returned to control levels. With labeling times of 4 hr or less, the iodoaminoacid distribution within these goiters still revealed the antithyroid action of AG, whereas 48 hr after labeling the distribution of the tracer on chromatograms was hardly any different from that usually reported for goiters produced by moderate iodine deficiency. Double labeling experiments using 125I, administered with the drinking water for 50 ...