GCG and Hyperglycemia: These observations should not, however, be extrapolated to the potential use of dipeptidyl peptidase-4 inhibitors (which inhibit the enzyme that inactivates GIP and GLP-1) to treat hyperglycaemia in the critically ill patient, because the efficacy of dipeptidyl peptidase-4 inhibitors may result in part from increases in intestinal and portal blood GLP-1 and GIP concentrations [40].