THE EFFECT OF IODIDE ON THE RELEASE OF THYROID HORMONE IN HYPERTHYROIDISM: FURTHER OBSERVATIONS*

Abstract

This study concerns the effect of iodide ion on the thyroid in 10 thyrotoxic patients. Seventy-two hours after a tracer dose of I¹³¹, treatment was started with 1-methyl-2-mercaptoimidazole and continued throughout the study. After seven days, sodium iodide was given orally, followed in some instances by administration of thyrotropin. By means of electrophoretic and chromatographic analyses, it was shown that the method employed allowed observation of the thyroid hormone secretion rate. It would appear that iodide inhibits the secretion rate by neutralizing thyrotropin at some point after pituitary release of thyrotropin. The data suggest that the hyperthyroidism observed in Graves’ disease is maintained, if not initiated, by a peripheral concentration of thyrotropin equal to that produced by the daily administration of no more than 6 mg. of thyrotropin daily.