GLP1R and obesity due to melanocortin 4 receptor deficiency: The recent finding that GIP/GLP-1 receptor co-agonists like tirzepatide have higher efficacy as compared with selective GLP-1 RAs as regards glycemic control and body weight, and the consequent approval for the treatment of T2D and obesity, reinvigorated interest in GIP, which in the past was thought to be without any therapeutic potential [25].