A healthy 24-year-old man partakes in a research study in which he is exogenously administered various concentrations of Factor X, followed by evaluation of pancreatic bicarb secretion. The results of his case study are shown. Which of the following hormones or enzymes is Factor X most likely to be?
Cholecystokinin
Gastrin
Glucose-dependent insulinotropic peptide
Secretin
Vasoactive intestinal peptide
