Insulin release, insulin sensitivity, and glucose intolerance.

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Abstract
Groups of subjects with different degrees of glucose intolerance were examined to determine, 1st, the capacity of the .beta.-cells to release insulin upon glucose stimulation and 2nd, sensitivity to insulin. The groups were selected on the basis of fasting blood glucose values and tolerances to oral and i.v. glucose administration. The body weights, ages and sexes of the subjects were well matched with those of control subjects with normal tolerances to oral and i.v. glucose administration. Computer analysis of the glucose and insulin curves during a standardized glucose infusion test made possible the measurement of the initiatory (parameters KI [immediate insulin release] and IP [insulin value at 10 min]) and potentiatory (parameter KP [potentiated insulin release]) effects of glucose on insulin release and of the sensitivity to endogenous insulin (parameter KG). In subjects with impaired oral, but normal i.v. glucose tolerance tests, KG was decreased, KP was increased, and KI and IP were normal. In these subjects, KI and IP were considerably lower than in a matched group of control subjects with the same decrease in KG, but with normal oral and i.v. glucose tolerance tests. In subjects in which both oral and i.v. glucose tolerance tests were impaired and in subjects with mild manifest diabetes, KI, IP and KG were decreased; KP was normal. All stages of glucose intolerance are accompanied by a decreased ability of glucose to initiate insulin release and by decreased sensitivity to insulin. These derangements seem to be partially compensated for by enhancement of the capacity of glucose to potentiate insulin release in subjects with decreased oral but normal i.v. glucose tolerance tests.