GLP1R and obesity due to melanocortin 4 receptor deficiency: Subsequent studies revealed that co-infusion of GLP-1 with GCG can mitigate the GCG-induced hyperglycaemia [34], while preserving GCG’s metabolic benefits, providing a strong rationale for the development of GLP1/GCG co-agonists as obesity treatments (Fig. 1) [15].