Localisation of gonadotropin-releasing and thyrotropin-releasing hormones in human brain by radioimmunoassay.

Abstract

Localization of gonadotropin-releasing hormone (GnRH) and thyrotropin-releasing hormone (TRH) in the human brain by radioimmunoassay is reported. The hypothalami and other brain regions were obtained during routine autopsies from 3 22-40 year old females and 12 41-95 year old males. GnRH concentration was highest in the preoptic area (340 pg/mg tissue) and declined progessively toward the caudal region which contained negligible amounts of GnRH. The highest concentrations of TRH were found in the posterior nucleus (158 pg/mg tissue) and the premammillary area. Exceedingly high concentrations of both hormones were in the pituitary stalk (1430 pg/mg and 855 pg/ml tissue for GnRH and TRH respectively). Total content of GnRH in the hypothalamus was 40.5 ng and in the pituitary stalk 58.6 ng. TRH content in the hypothalamus was 61.7 ng and in the pituitary stalk 35 ng. No apparent differences were observed in relation to age or sex. The absence of TRH in the lower 1/3rd of the pituitary stalk implies that it reaches the anterior pituitary by was of the long portal vessels whereas GnRH which is evenly distributed along the whole pituitary stalk and infundibular stem is transported via the long and short portal vessels.