Abnormal pancreatic alpha-cell function in first-degree relatives of known diabetics.

A standard intravenous glucose tolerance test utilizing a 25g glucose load was administered to 15 first-degree relatives of known diabetics and 19 normal control subjects with no known diabetic relatives. Despite normal glucose tolerance, 5 of the first-degree relatives had a significantly lower release of first-phase insulin (p 0.05). In contrast to 8 normal subjects and the remaining 10 first-degree relatives the secretion of glucagon by the 5 first degree relatives with abnormally low insulin release was not suppressed by induced hyperglycaemia. These findings provide evidence of abnormal alpha-cell function in a very early stage of genetic diabetes.