The Effect of Continuous Subcutaneous Insulin Infusion on Endogenous Insulin Secretion in Type I Diabetes

In an attempt to elucidate possible mechanisms for the success of continuous subcutaneous insulin infusion (CSII), we evaluated the C-peptide response to a standard breakfast in seven type I diabetic patients while they were on conventional insulin treatment and again after 4 wk of near-normal glycemia achieved with CSII. While on conventional therapy their 24-h mean blood glucose level was 211 ± 12 mg/dl and their glycosylated hemoglobin level was 10.6 ± 0.6%. After 4 wk of CSII their 24-h mean blood glucose level fell to 95 ± 7 mg/dl and their glycosylated hemoglobin level fell to 6.5 ± 0.4%. Plasma C-peptide levels were undetectable in all seven patients both while on conventional therapy and after 4 wk of CSII. We conclude that the success of CSII is related to an improved method of insulin delivery and not to either the selection of type I diabetic patients who have some residual insulin secretory capacity or to some change in endogenous insulin secretion produced by the treatment itself.