Influence of Age on the Intravenous Tolbutamide Response Test

Abstract

Intravenous tolbutamide response tests were performed on a selected group of 100 community-dwelling volunteer male subjects aged twenty-one to eighty-one years. A deterioration in performance with age was manifest as a progressively lesser fall and later nadir of blood glucose concentration throughout the early adult years and middle age. There was no further decrease in response after the sixth decade of life. Many investigations of the tolbutamide response test have been reported since the standards of normality for the test were introduced eight years ago. Those studies, in addition to the present report, show that the application of these standards to diverse population groups results in a very high percentage of “abnormal” or “diabetic” responses. We have considered the reasons for the large variation in response to intravenous tolbutamide reported in the literature. It appears that studies which report relatively large responses to tolbutamide are those in which the subject group was (a) composed predominantly of young adults, or (b) preselected on the basis of superior performance on glucose tolerance tests, or both. Data derived from this type of selection procedure provide standards of normality which are not applicable to the general population. We therefore propose a new approach to the interpretation of the results on the tolbutamide test: A set of nomograms is provided which permits the rapid computation of ageadjusted percentile ranking of an individual's response to intravenous tolbutamide.