PPY and obesity due to melanocortin 4 receptor deficiency: G‐protein coupled receptor subtype Y4R selective agonists have been proposed as anti‐obesity agents.[97] Natural neurohormone ligands of the human family of YxR (x=1, 2, 4, 5) G‐protein coupled receptors are neuropeptide Y (NPY) and pancreatic polypeptide (PP).