Abstract
It has been definitely shown that the normal structure of the thyroid gland is dependent upon an autacoid present in the anterior lobe of the pituitary gland. In amphibians its release at the time of metamorphosis stimulates the thyroid to excrete its content and induces the increased cellular activity characteristic of this period. In mammals Loeb and his coworkers 1 , 2 and Aron 3 , 4 showed that the injection of anterior pituitary extracts and emulsions produced also some characteristic changes in the thyroid suggestive of a higher activity. The follicular epithelium became higher, mitoses were present and colloid was excreted. The glands increased in size from 2 to 4 times and became more vascular. The metabolism of treated guinea pigs, as shown by Siebert and Smith 5 was markedly increased. As previous observations 6 had shown that young ducks were very sensitive to pituitary extracts and emulsions, it seemed worth while to investigate the possibility of inducing in this species functional and structural changes indicative of hyperthyroidism.
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