Low acute insulin response to intravenous glucose. A sensitive but non-specific marker of early stages of type 1 (insulin-dependent) diabetes.

Preventive treatment of Type 1 (insulin-dependent) diabetes presupposes early and accurate diagnosis of prediabetic states. The low acute insulin response to intravenous glucose has been proposed as a marker of both pre-Type 1 and pre-Type 2 (non-insulin-dependent) diabetes. In order to test the reliability of this marker for clinical detection of Type 1 diabetes we looked for this anomaly in 150 first degree relatives of Type 1 diabetic patients, 31 relatives of Type 2 diabetic patients and 39 young non-obese diabetic patients with mild or transient hyperglycaemia. The low acute insulin response was defined by a peak insulin value (sum of plasma insulin at 2 and 5 min after glucose load, 0.3 g/kg body weight) below 50 microU/ml. It was observed in 12% of the relatives of Type 1 diabetic patients (2 of them became diabetic) and in 13% of the relatives of Type 2 diabetic patients. Reproducibility of the peak insulin value in 2 subsequent tests (r = 0.749) was inadequate to interpret small variations in one individual. In the population of 39 diabetic patients, 10 subsequently developed typical Type 1 diabetes, 9 were low insulin responders. In the 29 patients who are still non-insulin-dependent 3 years later, the anomaly was found in the 3 islet cell antibody-positive subjects and 11 out of 26 patients with no detectable antibodies. In conclusion, low acute insulin response to glucose is a sensitive but non-specific marker of early stages of Type 1 diabetes as this anomaly is shared by both Type 2 and Type 1 diabetes.