GHRL and obesity due to melanocortin 4 receptor deficiency: The neurobiology of obesity is extremely complex and many novel potential antiobesity drugs and targets are identified including those acting on the central pathways as ciliary neurotrophic factor, melanocortin-4 receptor agonists, ghrelin, neuropeptide Y antagonists, melanin-concentrating hormone antagonists, or peptide Y [2,3].