Norepinephrine and TSH: effects on thyroidal radioiodine and thyroxine release.

Norepinephrine (NE) failed to increase thyroid hormone release in mice when endogenous TSH secretion had been greatly reduced by a variety of means. This was demonstrated by radioiodine release in mice pretreated with 131I and with thyroxine (T4) or 3,5,3' triiodothyronine (T3). by radioimmunoassay (RIA) in mice pretreated with 131I and T3, and in mice which had been hypophysectomized, or where TSH secretion had been decreased by prolonged administration of exogenous TSH. T4 could not be measured by RIA in mice pretreated with T4.