Plasma insulin studies in patients with lag curves.

The significance of the lag curve, i.e. one in which the blood sugar rises rapidly from a normal fasting value to more than 180 mg/100 ml but returns to the fasting value within 120 min, remains controversial. In order to study this further, plasma insulin levels were measured by immunoassay during oral and intravenous glucose tolerance tests in 3 groups of age/weight matched subjects: Group 1, 14 with unexplained lag curves: Group 2, 14 with lag curves following gastric surgery and Group 3, 14 normal subjects. The mean insulin levels were higher in Group 1 than in Group 3 but the hyperglycaemic stimulus was greater. The insulin response in Group 2 did not differ significantly from the controls. The mean blood sugar curves were similar in Groups 1 and 2, but despite this the insulin response was significantly prolonged in Group 1, suggesting a degree of insulin resistance or antagonism. In the intravenous test 2 patients from each of Groups 1 and 2 had aK value in the diabetic range. The meanK value was higher in Group 1 than in Group 2. Both groups showed a similar rather low insulin response.