The influence of stress conditions on the uptake of 131I by the rat thyroid

SUMMARY The uptake of 131I by the thyroid of the rat has been investigated under various conditions of stress. The acute change always consists in a considerable reduction of the rate of uptake of 131I irrespective of the nature of the stress. This acute inhibition in the uptake of 131I is independent of the anterior pituitary lobe, since it occurs in the normal and hypophysectomized animal alike. It is also independent of the presence of the adrenals. The inhibition of the uptake of 131I by the thyroids occurs in vivo only; their ability to take up 131I in vitro is not impaired. All the acute changes seen under stress conditions can be readily reproduced by treatment with adrenaline, which shows the same inhibitory effect on normal and hypophysectomized animals, the action being equally transitory. It is suggested that the acute changes in thyroid function seen under stress conditions are entirely independent of the anterior pituitary and are caused by increased release of vasoconstrictor substances. An increased uptake rate of 131I by the thyroid was seen 24 hr after the acute stress. This was thought to be caused by a compensatory increase in the secretion of thyrotrophic hormone by the anterior pituitary.