Methimazole: A Goitrogen Without Apparent Extrathyroidal Effects in the Rat

Abstract

Injection of 1.0 μg/100 g per day of l-thyroxine 1) prevented methimazole (Tapazole)-induced goiter in adult female rats without altering plasma PBI and 2) blocked thyroidal I¹³¹ release equally well in the presence or the absence of methimazole. The goitrogen did not alter the rate of degradation of labeled l-thyroxine, as manifested by urinary and fecal excretions of radioactivity. The data suggest that methimazole influences thyrotropin-thyroid hormone interplay without complicating effects of an extrathyroidal nature.