Tolbutamide Induced Insulin Release in Pregnant Diabetics

A study was undertaken to determine whether the abnormal insulin release pattern in insulin-independent pregnant diabetics (IID) was due to a lack of stored insulin and whether their clinical response to treatment with tolbutamide was correlated with enhanced plasma insulin values. Ten pregnant diabetics in the third trimester of pregnancy were subjected to both an oral glucose tolerance test and an intravenous tolbutamide tolerance test. The results indicated that an enhanced early release of insulin could be evoked by intravenous tolbutamide. The biochemical inertia of the beta cell noted in pregnant IID is therefore more likely to be associated with a relative insensitivity of the beta cell to glucose or to a defect in the enteroinsular axis. Although the individual hypoglycaemic effect of intravenous insulin was similar, the plasma insulin response varied greatly. The clinical improvement in tolbutamide-treated diabetics cannot be explained solely on the basis of enhanced insulin release.