Insulin responses to oral carbohydrate in true prediabetics and matched controls.

The definition of prediabetes by genetic criteria alone has limitations since not all such subjects progress to overt diabetes. Sequential oral glucose tolerance testing in a population has enabled the identification of 14 "true prediabetic" subjects with baseline two-hour plasma glucose levels smaller than 160 mg. per 100 ml. who subsequently developed unequivocal diabetes (two-hour plasma glucose level larger than 275 mg. per 100 ml.). All but one were matched for baseline two-hour plasma glucose and relative weight with a subject whose glucose tolerance remained unchanged during a mean follow-up period of 4 years. Fasting insulin levels and responses at 1/2, 1, and 2 hour sampling times were similar in both group and matched pair analysis at baseline. No evidence was found that subjects destined to develop diabetes have either excessive or diminished insulin secretion.