Radioimmunoassay and Chromatographic Similarity of Circulating Endogenous Gonadotropin Releasing Hormone and Hypothalamic Extracts in Man

Abstract

A highly sensitive radioimmunoassay for the gonadotropin releasing hormone has been developed in order to study its physiological importance in man. In view of the expected low concentrations in peripheral blood, large volumes of human plasma were extracted by two different methods and the characteristics of the radioimmunoassayable material compared with those of synthetic decapeptide and extracts of human hypothalami. The results indicate that radioimmunoassayable gonadotropin releasing hormone is present in some human plasmas but the plasma concentrations are less than 2.5 pg/ml. Peripheral levels were more consistently measurable in women at midcycle andafter the menopause. The hormone was undetectable in the plasma of normal men, human cerebrospinal fluid, and fetal cerebral tissue, but was present in fetal hypothalami.