Further support for heterogeneity of insulin response and insulin sensitivity in non-obese subjects with glucose intolerance

Abstract

Abstract. The relationship of insulin secretion and insulin sensitivity was studied in 67 age- and body weight-matched non-obese subjects, classified as having a normal glucose tolerance or glucose intolerance (50 g oral glucose load). Insulin response was studied by means of a 2 h glucose infusion. For the determination of insulin sensitivity a 1 h priming dose-constant insulin infusion technique was used. The per cent decrease of plasma glucose level at comparable steady-state insulin levels served as a measure of body sensitivity to exogenous insulin. In patients with glucose intolerance the early (ΔIRI area 0–5 min) and late (ΔIRI area 30–120 min) insulin responses to iv glucose were significantly reduced in comparison to controls. Controls and subjects with glucose intolerance showed considerable heterogeneity of insulin responses. Patients with glucose intolerance and relative insulin deficiency were not less responsive to insulin than subjects with normal glucose tolerance. There was, however, a wide variation of insulin sensitivity within the two groups. There was a weak significant inverse correlation between insulin response to glucose and insulin sensitivity for the two groups combined and for controls and subjects with glucose intolerance separately. The results demonstrate that the majority of non-obese patients with glucose intolerance and relative insulin deficiency does not exhibit a reduced responsiveness to insulin and therefore hypoinsulinaemia but not insulin resistance is the primary defect for an abnormal glucose tolerance in these group of subjects.