Abstract
Glucose tolerance tests (GTT) were performed and plasma insulin levels measured by immunoassay in eighty-nine subjects previously found to have non-diabetic glycosuria (fifty-six with renal glycosuria and thirty-three with lag curves). The time-interval between the two tests varied from 6 months to 13 years. Ten patients had developed chemical diabetes but only three had symptoms. Two had initially renal glycosuria and eight lag curves. This significantly different incidence may have been due to an excess of older patients in the lag-curve group. The mean insulin response was higher in those with diabetes than in those in whom the second test was normal. The individual insulin responses were abnormal by our criteria in twenty-six subjects including six of the ten diabetics. In twenty-four subjects plasma insulin levels had been measured during the initial GTT. The insulin response had been abnormal in thirteen of these, four of whom were diabetic at follow up. In contrast only one of the eleven subjects with an initially normal insulin response had developed diabetes. It is suggested that an abnormal insulin response to glucose may be an indication of potential diabetes.