Increase of Plasma TSH Concentration Following Injection of Purified Hypothalamic TRF

Abstract
A purified preparation of TSH [thyroid-stimulating hormone]-releasing factor (TRF), specific activity 30 U/ml, of sheep hypothalamus origin, elevates the levels of circulating plasma TSH from 21 to 197 mU/100 ml in 3 min. following intravenous injection in normal animals; even though less marked in amplitude, the same effect is seen in thyroidectomized animals. The material has no effect in hypophysectomized animals.