THE EFFECT OF CORTISONE AND CORTICOTROPIN ON THE RELEASE AND PERIPHERAL METABOLISM OF THYROID HORMONE1

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Abstract
Rat thyroid glands were labelled with I131 and further uptake blocked with propylthiouracil. The effects of cortisone and corticotropin on I131 release rates were studied, each animal being used as its own control. Corticotropin, 25 or 90 units subcutaneously 12 hourly was without effect. Two and one-half milligrams of cortisone subcutaneously 12 hourly doubled the I131 release rate. This increase was also present in hypophysectomized animals. Cortisone did not influence the acceleration of “release rate” produced by thyrotropin. It was concluded that this unexpected effect of cortisone is due in part to a direct action on the thyroid. The hypophysis may also be stimulated to produce excess thyrotropin. The effects of cortisone and corticotropin, in the same doses, on peripheral degradation of thyroxine, were investigated in rats, using intravenous thyroxine I131 and frequent blood sampling over a 72-hour period. Control and experimental groups were used.