Iodide Release from the Thyroid as an Acute Response to Epinephrine and Norepinephrine

The effects of epinephrine. norepinephrine and thyroid-stimulating hormone (TSH) on the release of plasma inorganic iodide¹³¹ from the thyroid gland were determined by catheterization of the thyroid vein and measurement of total plasma I¹³¹ and protein-bound I¹³¹ levels in the dog. Inorganic plasma I¹³¹ levels increased 60% or more in 5 of 6 dogs following epinephrine administration and in one of 3 dogs receiving norepinephrine. Two dogs receiving TSH iv had significant increases in thyroid vein inorganic I¹³¹. The inorganic I¹³¹ rise occurred simultaneously with increases in PBI¹³¹. Control experiments during a comparable experimental period failed to demonstrate significant changes in inorganic I¹³¹ levels. Administration of epinephrine to 2 hypophysectomized dogs yielded inconclusive results as to changes in inorganic plasma I¹³¹ levels.