Ghrelin is an endogenous ligand for the growth hormone secretagogue receptor that is synthesized principally in the stomach. It stimulates food intake and transduces signals to hypothalamic regulatory nuclei that control energy homeostasis. Ghrelin is present in the peripheral circulation in two forms: acylated and unacylated. The Ghrelin (rat unacylated) EIA kit is a competitive assay that can be used for quantification of the unacylated form of ghrelin in blood or plasma samples.