Ghrelin is a 28-amino-acid acylated peptide with an octanoic group on the serine residue. Ghrelin was primarily isolated from the rat and human stomach in 1999. Ghrelin is derived from a preproghrelin by posttranslational processing. Ghrelin has also been detected in the pituitary gland, kidney, lung, placenta and pancreas. The most important function of ghrelin in adult animals (rats) is to stimulate food intake, growth hormone secretion and motility. Ghrelin also enhances the cytoprotective effect in the gastrointestinal tract. Recent studies on newborn piglets showed that ghrelin reduces body weight and small intestine and villi length, and therefore slows the development of the neonatal intestine. Similar effects were observed in the stomach and small intestine in newborn rats but after weaning the results were quite the opposite. Studies in vitro showed a positive effect of ghrelin on cell proliferation and survival.