Ghrelin, also known as Obestatin, is the ligand for growth hormone secretagogue receptor type 1 (GHSR). It induces the release of growth hormone from the pituitary and involved in growth regulation. This protein has an appetite-stimulating effect, induces adiposity and stimulates gastric acid secretion. Ghrelin plays a significant role in neurotrophy, particularly in the hippocampus, and is essential for cognitive adaptation to changing environments and the process of learning.