It is also known that patients with some mutations can be successfully treated with well-known drugs; e.g., glucagon-like peptide 1 (GLP-1) agonist is effective in weight reduction in patients with MC4R mutations, and obesity related to Kinase Suppressor of Ras-2 (KSR2) mutation is well treated with metformin (21, 28, 30). Here, GCG is linked to obesity due to melanocortin 4 receptor deficiency.