GIP and obesity due to melanocortin 4 receptor deficiency: As the insulinotropic effect of GIP is diminished in patients with type 2 diabetes (T2D) (2), the therapeutic potential of the GIP axis has been relatively underexplored, whilst structurally optimised agonists of GLP-1 receptors (GLP1R) have been developed and introduced for the treatment of T2D and obesity.