Influence of Hypothalamus on Pituitary-Thyroid Axis in the Rat.

Abstract

In rats with anterior hypothalamic lesions the maximal circulating thyrotropin levels after goitrogen feeding are lover than in control animals as measured by bioassay based upon hormonal iodine discharge from chick thyroids. The discharge of labelled hormone from the thyroid of lesioned and control rats is inhibited by equal doses of exogenous thyroxine. This indicates that the thyroid-pituitary feedback system controlling TSH release is independent of the hypothalamus. In electrolytically lesioned rats with destruction of the thyroid-controlling hypothalamic area there do not appear to be major changes in the relative amounts of iodinated tyrosines and thyronines in the thyroid as have been shown to occur in cyclotron-lesioned rats.