Influence of ACTH on the Accumulation of Radioiodine in the Human Thyroid—A New Extra-adrenocortical Effect of ACTH

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Abstract
The time-response relationship between a single intravenous injection of adrenocorticotropic hormone (ACTH) and thyroid-stimulating hormone (TSH), and their effect on the initial accumulation of radioiodine in the thyroid, was studied in normal, adrenalectomized and adrenalectomized-hypophysectomized patients. The radioiodine uptake increased significantly in adrenalectomized patients 1/2, 1, 2 and 6 hours after intravenous injection of 25 IU ACTH (Acton, Ferring) and then returned to the initial level. Almost identical results were obtained from experiments using highly purified ACTH preparations from different laboratories. On the other hand, hypophysectomized, adrenalectomized- hypophysectomized and patients with normal endocrine function showed no increase in the uptake of radioiodine. Daily intramuscular injections of 25 IU ACTH (Acton prolongatum, Ferring) also produced a slight increase of the radioiodine accumulation during the period of observation (6 days). The effect of ACTH on the uptake of radioiodine in the thyroid was compared with that of TSH in the same group of patients. Following intravenous injection of 0.1 USP units TSH per kg body weight, the uptake increased slowly, was significantly higher after 3 hours, and reached its maximum after 24–36 hours. The difference between the effects of ACTH and TSH was significant. The increase of the uptake after ACTH was slighter, appeared sooner and disappeared more quickly, suggesting that it was a true ACTH effect and not one caused by contamination with TSH.