Ghrelin is a growth hormone secretagogue in fish

Ghrelin is a newly discovered multifunctional gut/brain hormone that is involved in the regulation of growth hormone (GH) release in mammals. Ghrelin and its receptor, the growth hormone secretagogue receptor (GHS-R) have been identified in several species of teleost fish. Ghrelin is mainly found in the gut of fish, while the GHS-R is mainly expressed in the pituitary and brain. Both mammalian and fish ghrelins stimulate GH release in vitro from the pituitary of fish. In addition, central and peripheral administration of ghrelin increases circulating levels of ghrelin in fish. The presence of the receptor and the in vitro and in vivo actions of ghrelin indicate that a ghrelin/GHS-R system is present in fish and ghrelin is an endogenous GHS involved in the regulation of GH release from fish somatotropes.