Thyroid Deprivation and Replacement in Chickens

THERE is evidence that both the thiouracil fed chick (Wentworth and Mellen, 1961) and the radiothyroidectomized (RTX) chick (Mellen and Wentworth, 1962) produce small amounts of labelled thyroid hormones following the injection of I131. Nevertheless, the studies of Mellen and Wentworth (1962) and Snedecor and King (1964) are in agreement that the hypothyroidism produced by the RTX treatment is severe on the basis of body weight, oxygen consumption, testis weight and serum cholesterol. The reductions in body weight and gonad weight are comparable in extent to the changes caused by surgical thyroidectomy (STX) by Simmons (1943), Blivaiss (1947), and Morris (1951). Mellen and Wentworth (1962) reported one experiment in which RTX was compared with thiouracil (0.1% of food) feeding. Although the effects were the same on oxygen consumption, thiouracil did not depress body weight as much as did RTX either at three weeks (84.3 % vs. 79.1% of control) or…