Peptide YY (PYY), a member of a neuropeptide Y (NPY family) is a 36 AA peptide secreted from the L cells of the gastrointestinal tract in response to food intake. The release of PYY is stimulated by nutrients within the lower small intestine and the colon, which in turn decreases food intake by inhibiting gut motility. It acts as an “ileal brake” to cause a sense of satiety. PYY3-36 is produced by the dipeptidyl peptidase-IV digestion of polypeptide YY (PYY).