GIP and obesity due to melanocortin 4 receptor deficiency: The advancement of multi-receptor drugs that mimic the glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and glucagon action, including semaglutide, tirzepatide, and retatrutide, has driven the pharmacotherapy of obesity to a new era of effectiveness [6,7].