Serum insulin response to intravenous administration of 1 mg. glucagon and 25 or 40 gm. glucose plus 1 mg. glucagon has been studied in normal and markedly obese nondiabetic patients and compared to the responses of infusions of glucose alone.
In both groups, serum immunoreactive insulin (IRI) rose to a maximal level within five minutes after the end of each injection, but the rise was significantly higher in the obese subjects. In spite of the augmented rise of IRI after a glucose plus glucagon infusion, the mean rate of glucose disappearance did not change significantly in the obese subjects, a finding which suggested impaired sensitivity to endogenous insulin. In obese subjects, who are known to have hyperplasia of the islets of Langerhans, the enhancement of insulin secretion by glucagon appears greater.