Effects of diethylstilbestrol with thyroxin or thiouracil on thyroid in male rats

¹ Department of Animal Industry and Nutrition, The Pennsylvania State University, University Park, Pennsylvania

Sixty-six normal or castrate young male rats were used, as replicates of three or four animals each; they were subjects for equalized feeding, within replicates, of a basal diet with no additives, and a basal diet with additives per gram of diet of 0.6 µg diethylstilbestrol (DES) and 1 µg l-thyroxin or 1 mg thiouracil. Criteria evaluated were weight gain, feed efficiency, body length, and size of pituitary, thyroid, adrenals, and testes. DES produced significant reductions in weight gain, feed efficiency, and size of testes, and significant increases in size of pituitary, thyroid, and adrenals. Responses of castrate animals to DES were altered in the same direction as those of normal animals; all differences, except for thyroid, were significant. Castrate DES-treated animals exhibited smaller weight gain and feed efficiency, and less thyroid hypertrophy than normal DES-treated animals. Thyroxin overcame a significant portion of DES-induced thyroid hypertrophy; it significantly further depressed the feed efficiency of DES treatment alone. Thiouracil produced the expected thyroid enlargement, and significantly increased weight gain, feed efficiency, and size of pituitary and testes in DES-treated rats; it significantly reduced body length and adrenal size.