The absolute antecedent of circulating ghrelin is the gastrointestinal tract, primarily from the stomach, but aswell in abate amounts from the intestine. The hypothalamus in the academician is addition cogent antecedent of ghrelin; abate amounts are produced in the placenta, kidney, and pituitary gland.
The ghrelin receptor was accepted able-bodied afore ghrelin was discovered. Cells aural the antecedent pituitary buck a receptor that, if activated, potently stimulates beard of advance hormone - that receptor was called the advance hormone secretagoue receptor (GHS-R). The accustomed ligand for the GHS-R was appear in 1999 as ghrelin, and ghrelin was called for its adeptness to abet advance hormone secretion.
Ghrelin's action in modulating agriculture behavior and activity antithesis are best explained by the attendance of ghrelin receptors in areas of the hypothalamus continued accepted to be complex in appetence regulation. Receptors are aswell begin concentrated in added areas of the brain, including the hippocampus and regions accepted to be complex in accolade systems (e.g. tegmental area); indeed, ghrelin appears to actuate some of the aforementioned circuits that are complex in biologic reward, which may aswell be accompanying to this hormone's furnishings on appetite.