Chick Thyroid Size and Incubation Period as Influenced by Thyroxine, Thiouracil and Thyroprotein

Abstract

GOITEROGENIC substances such as thiourea and thiouracil have been shown by numerous workers to produce enlarged thyroid glands in several classes of experimental animals. These substances prevent the formation of thyroxine by the thyroid gland (Astwood et al. 1943), and as a result the thyroid gland hypertrophies due to the increased secretion of the thyrotropic hormone. The studies of Larson et al. (1945) with radioactive iodine have confirmed these conclusions and have shown that thiouracil prevents the thyroid gland from utilizing iodine to form thyroxine. Pregnant rats fed a ration containing thiourea have been reported by Goldsmith et al. (1945) to produce offspring with thyroid hyperplasia. Andrews and Schnetzler (1945) fed thiouracil to hens in a ration at a level of 0.2 percent and found that chicks with goiterous thyroid glands were produced. Evidence was submitted indicating that thiouracil is transmitted through the egg to the developing chick. Changes in . . .