Whenn oral glucose tolerance test is done on a subject who has had a gastric operation for peptic ulcer, an abnormal response may be obtained. The blood glucose curve shows a rapid rise to abnormally high levels and then a fall to normal or to hypoglycemic levels after two hours. Symptoms of hypoglycemia may occur during the phase of falling blood glucose levels. This type of response, often referred to as the lag curve or the curve of alimentary hyperglycemia, may also be observed in otherwise healthy individuals or in thyrotoxic patients. If such a curve is found in a healthy patient, periodic retesting is advisable to detect possible progression to a diabetic curve.
The cause of the lag curve in postgastrectomy patients is presumed to be the rapid absorption of glucose from the jejunum secondary to rapid transit from the stomach. If this were so, then there would be