The thyrotropin-releasing hormone (TRH) is a molecule with widespread distr
ibution through many organ systems. The function of TRH is probably not ide
ntical in each system so that TRH synthesis and secretion may be unique for
each system under specific experimental conditions. The present study was
designed to explore the common and diverse features of the regulation of TR
H encoded with the same gene in two different organs: hypophysiotropic hypo
thalamus and pancreatic islets. During in vitro incubation, the TRH content
in hypothalamic structures remained stable while that in isolated pancreat
ic islets increased sharply. In contrast to the pancreatic islets, exposure
to different concentrations of D-glucose did not affect TRH release from t
he hypothalamic paraventricular nucleus or median eminence. This divergence
in the regulation of the hypophysiotropic and pancreatic TRH systems may b
e related to differences in the role of TRH produced in these tissues.