THE GHRELIN SYSTEM; BEYOND THE ROLE IN ENERGY HOMEOSTASIS

The fascinating story of ghrelin started more than 30 years ago with the discovery of synthetic (non-natural) growth hormone (GH) releasing peptides. Scientists were searching for a novel peptide, ligand of orphan GH secretagogue receptor. The discovery of ghrelin is a typical example of reverse pharmacology. The new peptide quickly attracted a lot of attention by its pleiotropic nature, and provoked a burst of new enthusiasm among scientists and clinicians. Ghrelin is mainly produced in the stomach from a distinct group of endocrine cells located within the gastric oxyntic mucosa. It acts as hunger signal and long-term body weight regulator. But, ghrelin is much more than just a natural orexigenic factor and GH secretagogue. It exerts major peripheral endocrine and non-endocrine actions, and it has a role in learning and memory, glucose homeostasis, immunity, cardio protection, fertility and addiction. Exploring the actions of ghrelin and ghrelin agonists and receptor antagonists or reverse agonists could establish new treatment options for so far incurable diseases