SOME EFFECTS OF THE HYPOPHYSIS ON IODINE METABOLISM BY THE THYROID GLAND OF THE RAT

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Abstract
The administration of thiouracil to the rat results in hypertrophy and hyperplasia of the thyroid gland and in decrease in thyroid iodine content, and these effects are dependent on the integrity of the pituitary gland (Astwood, 1944–45). Continued administration of thiouracil results in a state of hypothyroidism due to inhibition of thyroid hormone formation, and the thyroid gland changes are compensatory in nature, the result of increased elaboration of thyrotropic hormone by the pituitary. Thyroid glands rendered hyperplastic through the chronic administration of thiouracil are able to accumulate large amounts of iodine following injection of potassium iodide into the intact rat (Astwood, 1944–45), although this iodine can be retained for but a short time (VanderLaan and Bissell, 1946) and remains in ionic form (VanderLaan and VanderLaan, 1947). Thus, iodine can be concentrated by the thyroid gland despite the inhibition of its incorporation into thyroid hormone by the antithyroid agent.