Gastric inhibitory polypeptide (GIP), immunoreactive insulin (IRI), and glucose levels in response to orally administered glucose were determined in ten patients with vagotomy and pyloroplasty (V&P) and in 21 normal subjects. The V&P patients had the expected early and exaggerated increase in mean serum glucose with a subsequent decline to a level below fasting. The early mean GIP response was similarly elevated and paralleled the glucose response. The early mean serum IRI of V&P patients was greater than that of normal subjects, but only at 30 minutes was the difference statistically significant (P<.01). Since GIP is known to be insulinotropic, the results of this study suggest that its role in the enteroinsular axis is magnified after V&P. The GIP may be in part responsible for the postprandial hypoglycemia recognized clinically as the "late phase" of the dumping syndrome.
Thomford NR, Sirinek KR, Crockett SE, Mazzaferri EL, Cataland S. Gastric Inhibitory PolypeptideResponse to Oral Glucose After Vagotomy and Pyloroplasty. Arch Surg. 1974;109(2):177-182. doi:10.1001/archsurg.1974.01360020039009