GCG and type 2 diabetes mellitus: Currently there are several types of treatment for T2DM, including OADs such as metformin, sulfonylureas, thiazolidinediones, alpha-glucosidase inhibitors, meglitinides, and dipeptidyl peptidase-4 (DPP-4) inhibitors; glucagon-like peptide-1 (GLP-1) receptor agonists; and insulin; and they can be used as monotherapy or in combinations to arrive at the best individualized treatment plan to achieve treatment goals [8,12,13].