[1] It is an ancient, highly conserved protein whose origin predates the divergence of protostomes and deuterostomes.
[2] Corticotropin-releasing hormone (CRH) plays multiple roles in vertebrate species.
It is the major hypothalamic releasing factor for pituitary adrenocorticotropin secretion,[2] and is a neurotransmitter or neuromodulator at other sites in the central nervous system.
In non-mammalian vertebrates, CRH not only acts as a neurotransmitter and hypophysiotropin, it also acts as a potent thyrotropin-releasing factor,[3] allowing CRH to regulate both the adrenal and thyroid axes, especially in development.
Corticotropin-releasing factor binding protein (CRH-BP) is thought to play an inhibitory role in which it binds CRH and other CRH-like ligands and prevents the activation of CRH receptors 1 and 2.