1) Ghrelin was first discovered as the endogenous ligand for the growth hormone secretagogue receptor (GSH-R). 2) Contrary to initial expectations, ghrelin was isolated from stomach extracts, not the pituitary or hypothalamus. 3) Subsequent research found that ghrelin stimulates food intake and appetite in rodents when injected into the bloodstream or brain, and that ghrelin levels rise with fasting and fall after eating.