Glucose tolerance, insulin secretion, and glucose utilization in subjects after gastric surgery

Oral and intravenous glucose tolerance tests were administered to normal subjects and patients postgastric surgery. Chemical and symptomatic hypoglycemia occurred in 18 of 25 subjects with prior gastric surgery during the oral glucose tolerance tests. These hypoglycemic study patients had higher peak (P < 0.003) and greater total (P < 0.001) serum insulin concentrations than the nonhypoglycemic patients; however, peak plasma glucose levels and the rate of glucose absorption were similar in both postgastrectomy subgroups. During the oral glucose tolerance tests, the peak and total serum insulin concentrations in all study patients correlated significantly with the lowest observed plasma glucose levels (P < 0.05), but peak plasma glucose levels did not correlate with either serum insulin concentrations or the lowest plasma glucose levels. Kg values, derived by intravenous glucose tolerance tests, were lower in the postgastrectomy patients than young, normal adult subjects (P < 0.005); however, the Kg values in the postgastrectomy group did not correlate with any parameter of the oral glucose tolerance tests. Following glucose ingestion, the lowest plasma glucose levels in subjects with prior gastric surgery can be related to plasma insulin concentrations, but early increments in plasma glucose levels or absolute plasma glucose levels cannot explain observed insulin secretion. Kg values, from intravenous glucose tolerance tests in these patients, do not correlate with any abnormality of oral glucose tolerance: thus, the chemical diagnosis of diabetes mellitus in the patient with prior gastric surgery may require reevaluation.