Counterregulatory responses in CSII

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Normally, glucose is the only substrate used by the brain to meet its metabolic requirements. Therefore, a continuous supply of circulatory glucose is a necessary prerequisite for normal cerebral metabolism. Acute hypoglycemia produces several physiological responses, known as counterregulatory, symptomatic and behavioral responses, that aim at preventing further decrease in plasma glucose and thus correct hypoglycemia. Subjects with type 1 diabetes mellitus under intensive insulin treatment either with multiple daily injections (MDI) or with continuous subcutaneous insulin infusion (CSII) exhibit defects in these responses, mainly the adrenaline response, which may increase the recurrence of hypoglycemia in daily life. Unfortunately, recurrence of hypoglycemia [i.e. blood glucose < 70 mg/dl (3.9 mmol/L)], including mild hypoglycemia, does further impair such hormonal responses and the awareness of hypoglycemia resulting in additional risk for severe hypoglycemia. CSII, which for several reasons, including subjects' preferences and higher costs, is less widespread than MDI, allows achievment of good glycemic control while reducing the risk of hypoglycemia and of hypoglycemia induced blunted counterregulatory and symptomatic responses (hypoglycemia-associated autonomic failure). For that reason, CSII would be particularly indicated in people suffering from recurrence of severe hypoglycemia and hypoglycemia unawareness under a MDI treatment regimen.