The isolation of thyrotropin-releasing hormone (TRH, protirelin) in 19691,2 allowed an initial definition of specific biochemical mechanisms by which the brain regulates the release of pituitary hormones. The neuroendocrine role of TRH (initiating the pituitary release of thyrotropin) still remains as the best resolved physiologic function of this tripeptide molecule.3
See also p 1149.
The name "thyrotropin-releasing hormone," reflecting this hypophysiotropic action, is perhaps overly restrictive in light of further discoveries during the last 15 years. It has been demonstrated that TRH and its receptors are widely distributed within the CNS and in peripheral organs, and that the numerous pharmacologic effects of this substance include potent actions on autonomic, somatic, and behavioral systems.3-5 These properties of TRH are independent of its pituitary-thyroid involvement and seem to indicate that TRH has more universal functions as a neuromodulator. The pharmacologic use of TRH may therefore prove to have great