GCG and obesity due to melanocortin 4 receptor deficiency: The twincretin tirzepatide is a novel dual glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) receptor agonist approved by the FDA in May 2022 for the treatment of T2DM, based on the results of the Study of Tirzepatide in Participants with T2DM Not Controlled with Diet and Exercise Alone (SURPASS) clinical trials [103,104]; benefits in patients with obesity were also proved later [105].