Age‐Related Insulin Patterns in Normal Glucose Tolerance*

Abstract

ABSTRACT: In 707 non‐obese female adults with unimpaired glucose tolerance, the fasting blood glucose levels of those in the fourth, fifth and sixth decades of life exceeded the levels found in those of the third decade (20–29 years), but there was no evidence of a progressive increase in successive age decades. The slightly greater fasting glycemia in the later age decades was accompanied by higher increments in blood glucose in the first half hour of the glucose tolerance test. These higher levels of glucose during the fasting state and in the first half hour after oral administration of glucose were not associated with increments in serum insulin greater than those recorded for the third age decade. This age‐related increase in fasting and post‐glucose blood sugar levels without an increase in serum insulin could result from the age‐related increase in the thickness of capillary basement membranes. The higher levels of glucose could then serve to restore glucose transport and cell glucose metabolites to normal without evoking a rise in serum insulin. In 479 obese women with unimpaired glucose tolerance, there was no evidence of the age‐related increase in fasting blood glucose nor the slightly exaggerated hyperglycemia found early in the test in non‐obese subjects with normal glucose tolerance. The relative fasting hyperinsulinemia and the increased insulin responses to induced hyperglycemia known to characterize obese persons were present in all age decades but the hyperinsulinemia was less marked in subjects older than 30. In these obese subjects with unimpaired glucose tolerance, there was no evidence of any delay in the insulin response to the induced hyperglycemia.