The influence of radioactive iodine upon the nonstimulated and stimulated thyroid gland

Summary

Administration of a single 1 μ C I¹³¹ dose to albino male rats provokes considerable changes in their thyroid glands and marked alterations in the physico-chemical composition of the cytoplasm and karyoplasm of the thyroid epithelium. In the first 2 days this is manifested in the dislocation of the isoelectric point of the above cellular components toward increased acidity, in the intensified neutral red sorption, in the increased mean height of follicular cells and the mean relative crude weight of the gland.

The aforementioned changes proved more pronounced in the thyroid gland previously activated by the action of 6-methylthiouracil. With the continuing 6-methylthiouracil action on the thyroid gland after radioiodine injection, the thyroid parenchyma becomes a scene of the following pathological changes: marked polymorphism of the follicular epithelium cells, large perinuclear vacuolization, a rise in the number of nuclear pycnoses and karyorrhexis and, here and there, desquamation into the follicular cavity. Thus, radioiodine affects both the unstimulated and stimulated thyroid; in the latter case the effect is considerably intensified even by small doses of radioiodine.