The Full form of PP is Pancreatic Polypeptide. The pancreas is a gland, having both a digestive exocrine and an endocrine function. As an endocrine gland, it functions mostly to regulate blood sugar levels, secreting the hormones insulin, glucagon, somatostatin, and pancreatic polypeptide. PP is a thirty six amino acid peptide produced and secreted by PP cells (originally termed F cells) of the pancreas which are primarily located in the Islets of Langerhans. It is part of a family of peptides that also includes Peptide YY (PYY) and Neuropeptide Y (NPY). PP is rapidly released after a meal but remains elevated for four to six hours in humans with the Vagus nerve being the major stimulator. PP has effects on GI motility, metabolism and food intake. A potential role as a satiety factor comes from the observation that PP secretion is absent in obese children with Prader-Willi syndrome. Its primary action on the exocrine pancreas is to inhibit secretion in vivo by acting on receptors in the brain leading to inhibition of vagal output to the pancreas. The function of PP is to self-regulate pancreatic secretion activities (endocrine and exocrine). It also has effects on hepatic glycogen levels and gastrointestinal secretions.