GCG and diabetes mellitus: Interestingly, whereas GLP-1 content in non-diabetic human islets is only a fraction of that of glucagon (<1%) (Galvin et al. 2021), its secretion was significantly higher in islets from type 2 diabetic (T2D) donors than from euglycaemic donors, indicating that there may be a switch not only in glucose sensitivity but also in α-cell qualitative hormonal output in diabetes.