THE EFFECT OF EXCESSIVE IODINE ON THE THYROID OF THE RAT

Abstract

The immediate effect of large single doses of iodine on thyroid function in the rat has been studied with the aid of I131 and chromatographic analysis. Organic binding of iodide is initially depressed, but the effect wears off after 16 hours presumably as the plasma iodide declines. The ratio of monoiodotyrosine to diiodotyrosine is elevated at the time of minimal binding. Long term treatment (7 weeks) of rats with iodide results in an initial suppression of I131 binding in the thyroid. The effect has disappeared after 3-4 days but iodide binding falls slowly during the ensuing weeks. There is little or no evidence of hypothyroidism in these animals.