Further, the structure and composition of glucagon, i.e., its single chain 29 amino acids peptide sequence devoid of any disulfide bonds made this a feasible approach to understand glucagon physiology and pathophysiology in type 1 diabetes where major abnormalities in circulating glucagon concentrations occur during various free-living conditions, e.g., fasting, postprandial and exercise. Here, GCG is linked to type 1 diabetes mellitus.