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, which is effective in weight reduction in patients with MC4R mutations, and obesity related to Kinase suppressor of Ras 2 mutation is well treated with metformin [51,52]. Here, GCG is linked to obesity due to melanocortin 4 receptor deficiency.