Background: Gastrointestinal hormones regulate intestinal transit, control digestion, influence appetite and promote satiety. Altered production or action of gut hormones, including glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and peptide YY (PYY), may contribute to the biological basis of obesity and altered glucose homeostasis. However, challenges in analytical methodology and lack of clarity on expected values for healthy individuals has limited progress in this field. The aim of this study was to describe expected concentrations of gastrointestinal and pancreatic hormones in healthy volunteers following a standardised meal test (SMT) or 75g oral glucose tolerance test (OGTT). Methods: 28 healthy volunteers (12 men, 16 women; mean age 31.3 years; mean body mass index 24.9 kg/m2) were recruited to attend a hospital clinic on two occasions. Volunteers had blood sampling in the fasting state and were given, in randomised order, an oral glucose tolerance test (OGTT) and standardised mixed liquid meal test with venepuncture at timed intervals for 4 hours after ingestion. Analytical methods for gut and pancreatic hormones were assessed and optimised. Concentrations of gut and pancreatic hormones were measured and used to compile ranges of expected values.

Results: Ranges of expected values were created for glucose, insulin, glucagon, GLP-1, GIP, PYY and free fatty acids in response to a standardised mixed liquid meal or OGTT. Intact Proinsulin and C-peptide levels were also measured following the OGTT. Conclusions: These ranges of expected values can now be used to compare gut hormone concentrations between healthy individuals and patient groups.