Effect of Stress and Cortisone on Plasma Protein-Bound Iodine and Thyroxine Metabolism in Rats

The plasma protein-bound iodine concentration of the intact rat is decreased after prolonged fasting, exhausting exercise and exposure to cold. This effect is not merely a result of suppressed thyroid function, since exercise and cold stress increase the rate of disappearance of injected thyroxine in thyroidectomized rats. Cortisone reduces the rate at which thyroxine is removed from the plasma, and can prevent the increase in the rate of disappearance of the hormone which is normally produced by exposure to a cold environment.