Identifying hyperinsulinaemia in the absence of impaired glucose tolerance: An examination of the Kraft database

•Hyperinsulinaemia is associated with many metabolic diseases, including vascular disease.•We examined a large database of more than 7000 oral glucose tolerance tests with insulin assay.•People with type 2 diabetes or impaired glucose tolerance have high and sustained insulin levels.•Most people with normal glucose tolerance have high insulin levels independent of obesity.•Dynamic insulin patterning may be a useful tool for diagnosing hyperinsulinaemia.

ObjectiveHyperinsulinaemia is associated with development of chronic metabolic disease and is emerging as a health risk independent to that of insulin resistance. However, little is known to what extent hyperinsulinaemia occurs with normal glucose tolerance in lean subjects.MethodOral glucose tolerance tests with concurrent insulin assay were conducted during the 1970s-1990s. Participants were classified according to glucose tolerance and insulin response pattern. Analysis of variance compared differences in plasma glucose, plasma insulin, and demographic and metabolic risk factors between groups.ResultsParticipants with normal glucose tolerance comprised 54% (n = 4185) of the total cohort. Of these, just over half (n = 2079) showed hyperinsulinaemia despite normal glucose clearance. Obesity had a modest association with hyperinsulinaemia in people with normal glucose tolerance. Fasting insulin had limited value in diagnosing hyperinsulinaemia. The majority of participants (93%) with impaired glucose tolerance or diabetes had concurrent hyperinsulinaemia.ConclusionHyperinsulinaemia in the absence of impaired glucose tolerance may provide the earliest detection for metabolic disease risk and likely occurs in a substantial proportion of an otherwise healthy population. Dynamic insulin patterning may produce more meaningful and potentially helpful diagnoses. Further research is needed to investigate clinically useful hyperinsulinaemia screening tools.