Age Differences in the Intravenous Glucose Tolerance Tests and the Response to Insulin

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Abstract
Intravenous glucose tolerance and glucose-insulin tolerance tests were performed on 35 normal male subjects under standardized conditions using venous blood samples. The subjects ranged in age from 23 to 86 years. Blood samples drawn at 5-minute intervals, between 5 and 60 minutes after administration of 25 g glucose, were analyzed for glucose by the Nelson method. The rate of fall of the blood sugar level between 10 and 60 minutes was determined by fitting the experimental points to the equation logey=logeA-kt. A significant decrease in k with age was seen in both the glucose and the glucose-insulin tolerance curves. Administration of insulin had a greater effect on the rate of disappearance of glucose from the blood in the young than the old subjects. It is proposed that the age difference may result from both a reduction in the amount of functioning protoplasm and an alteration in intra-cellular glucose metabolism.