Influence of Cortisone on Thyroid-Pituitary Interaction in Normal and Goitrous Rats.

Abstract

The subcut. admn. of cortisone (2.5 mg. daily, 18-24 days) potentiated propylthiouracil (PTU) induced goitro-genesis in adult female rats. Cortisone and PTU (0.05 % in ration) given concurrently for 18 days resulted in larger thyroids (34%) and higher blood TSH levels (stasis tadpole method) than with PTU alone. Adenohypophyseal TSH concn. was substantially reduced with or without cortisone. The effect of the steroid in goitrous rats was more marked if PTU was given for 106 days before admn. of cortisone (24 days). Thyroid hyperplasia was twice greater than with goitrogen alone, and approximated 1700% of normal. Pituitary enlargement also occurred which was significantly greater in the cortisone-PTU group. TSH concn. in the pituitary of longterm PTU treated rats was reduced still further with lowest values found in cortisone-PTU animals. Blood TSH levels were now elevated equally. The depressed avidity of thyroid tissue for I131 (with PTU) was not influenced by cortisone. The results indicate that the potentiating action of cortisone on PTU-induced goitrogenesis involves augmentation of TSH secretion from the adenohypophysis.