INDUCTION OF HYPOGLYCEMIA UNAWARENESS BY ASYMPTOMATIC NOCTURNAL HYPOGLYCEMIA

Hypoglycemia has been incriminated as a possible factor responsible fo r development of the hypoglycemia unawareness phenomenon in patients w ith type I diabetes. Many patients with this condition, however, do no t have a history of recent hypoglycemia. Because asymptomatic nocturna l hypoglycemia commonly occurs in type I diabetes, we tested the hypot hesis that such episodes might be capable of inducing this phenomenon. Accordingly, autonomic and neuroglycopenic symptoms, counterregulator y hormone responses, and cognitive function were assessed during stand ardized insulin-induced hypoglycemia in 10 normal volunteer subjects o n two occasions-once after induction of asymptomatic nocturnal hypogly cemia and once after control studies in which saline rather than insul in was infused overnight. Compared with control experiments, asymptoma tic nocturnal hypoglycemia increased the threshold (required greater h ypoglycemia for initiation) and reduced the magnitude of autonomic and neuroglycopenic symptoms, counterregulatory hormone responses, and co gnitive dysfunction during subsequent hypoglycemia (all, P < 0.05). Th ese results indicate that asymptomatic hypoglycemia may induce hypogly cemia unawareness and, thus, may explain why not every patient with th is condition has a history of prior hypoglycemia. Our results therefor e support the concept that in type I diabetes this phenomenon may be l argely attributable to antecedent hypoglycemia.