Abstract
Although gonadectomy in the rat is followed by an increase in the amount of gonad-stimulating principle in the anterior pituitary (Engle, Evans and Simpson) it is said that thyroidectomy does not cause any change in the amount of thyroid-stimulating hormone in the anterior pituitary of the rat, guinea pig and dog. 1 , 2 In our experiments we have compared the concentration and, in a preliminary way, the total amount of thyroid-stimulating hormone in the anterior lobes of thyroidectomized and control rabbits.
Thirty-one male rabbits (14 completely thyroidectomized and 17 control animals) and 28 female rabbits (10 completely thyroidectomized and 18 control animals) were used. There were available litter-mate controls for 7 of the thyroidectomized males and for 6 of the thyroidectomized females; other controls were from the same stock and of approximately the same age as the operated rabbits. The average time elapsing between thyroidectomy and death was about 4 months. The amount of thyroid-stimulating hormone in the anterior pituitary of a thyroidectomized rabbit was compared with that in the anterior pituitary of a control by injecting the same dose (usually 6 to 8 mg.) over a period of 4 days into litter-mate immature guinea pigs which were killed 24 hours after the last injection (on the 5th day) for histological examination of the thyroids. In some experiments, the doses injected were proportional to the weights of the donors'anterior lobes. In control experiments total doses of 4 mg. of fresh rabbit anterior lobe could be shown to stimulate the thyroid of the immature guinea pig.
In only 36.8 ± 9.11% of the pairs of guinea pigs receiving male anterior lobe, a greater thyroid-stimulation was caused by the anterior lobes of thyroidectomized rabbits.
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