Disappearance Rate and Distribution of Exogenous Thyrotropin in the Rat

Abstract

The disappearance and the distribution volume of injected bovine, rat and human thyrotropin were measured in hypometabolic, normal and hypermetabolic rats, with and without renal circulation. The disappearance of thyrotropic activity from the serum did not depart significantly from linearity on a semilogarithmic plot. The major roles of the metabolic rate and of renal tissue were confirmed. Thyrotropin was also concentrated in the liver and, for the first time, was demonstrated in the hypothalamus and to a slight extent in the thyroid gland. Insignificant amounts also were found in the urine. The pituitary glands showed an unexpected increase in thyrotropic activity after the injection of thyrotropin.