EFFECTS OF UNDERFEEDING ON THIOURACIL ACTION IN RATS AND MICE

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Abstract
The influence of underfeeding on the response of the thyroid gland to either constant or varied amts. of thiouracil was detd. in 58 mature female rats and in 59 mature and immature male mice. Thiouracil was injected subcut. in the form of an aqueous suspension at the rate of 10 mg. daily or was fed in the ration as a 0.1 or 0.2% mixture. Food intake was restricted by feeding either 3/4 or 1/2 of the feed consumed daily by ad libitum-fed controls. On a 100 g. body wt. basis, the underfed and ad libitum-fed animals which received the same amt. of thiouracil showed the same increases in thyroid wt., while the animals which received less thiouracil showed reduced thyroid responses. These results suggest that thyroid secretion in underfed rats and mice is reduced only in proportion to loss in body wt.