Glucagon-like peptide-1 (GLP-1) receptor agonists and the dual GLP-1- and glucose-dependent insulinotropic polypeptide receptor co-agonist tirzepatide (referred to here collectively as “GLP-1-based therapy”) are incretin-based therapies being used increasingly in the management of both type 2 diabetes and obesity. The gene discussed is GLP1R; the disease is obesity due to melanocortin 4 receptor deficiency.