HYPOTHYROIDISM PRODUCED BY THE FORCED FEEDING OF NORMAL RATS1

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Abstract
Normal rats were either force-fed or allowed to eat ad libitum a moderate carbohydrate diet for 3-4 weeks. The amount of food given to the force-fed groups was adjusted to maintain a rate of weight gain equal to that of the animals eating ad libitum. At the end or during the feeding period, several parameters of thyroid function were measured, namely, thyroidal I131 uptakes, the thyroid/ serum (T/S) concentration ratios for radioiodide, the percent of administered I131 converted to serum PBI131 and the rate of thyroid regeneration after hemithyroidectomy. These criteria of thyroid function indicate that force feeding produces hypothyroidism. On the basis of T/S ratios and thyroid weights, the diminished thyroid activity associated with tube feeding seems to be secondary to decreased TSH release as a result of hypofunction of the anterior pituitary.