Diffuse and Nodular Hyperplasia of the Thyroid Gland in Thiouracil-treated Rats

Abstract

Rats were fed a basic diet of ground Purina Dog Checkers containing 0.1% thiouracil. Controls received the basic diet. All animals were inoculated intra-perit. after 34, 51, or 85 days, respectively, with 2 ml. of an 18-hr. broth culture of the L4 strain of pleuropneumonia-like organisms. In some expts., the basic diet was substituted for the thiouracil diet at the time of inoculation. The animals were killed and their thyroid glands weighed and studied histologically. Animals which had received thiouracil for long periods of time had extreme thyroid gland hypertrophy. The time of inoculation or infection of the microorganisms did not affect the thyroid gland. Glands from animals receiving no thiouracil were normal. Glands from animals removed from the thiouracil diet after 34 or 51 days and placed on the control diet showed no hyperplasia. Thyroids from all animals on thiouracil diets for 120 days or more were distinctly hyperplastic with nodular hyperplasia. In animals which received thiouracil for 120 and 142 days, the numbers of discrete hyperplastic nodules were 2 and 3, respectively. Fifteen nodules were found in the thyroids of 7 of 24 animals which received thiouracil for 233 days. The epithelium within the areas of nodular hyperplasia had high cuboidal rather than ,, columnar cells and the nuclei were less vesicular and more deeply stained.