NOCTURNAL VERSUS DIURNAL HORMONAL COUNTERREGULATION TO HYPOGLYCEMIA IN TYPE-1 (INSULIN-DEPENDENT) DIABETIC-PATIENTS

Asymptomatic hypoglycemia in IDDM patients seems to be more frequent during the night than during the day, with reported frequencies as high as 56%. Hormonal counterregulation to diurnal and nocturnal hypoglycemia was studied in 10 insulin-dependent diabetic patients without diabetic complications in order to test whether hormonal responses were lower at night than during daytime. A lower catecholamine response might imply less marked symptoms and therefore one reason why patients are not awakened by hypoglycemia. Blood glucose was stabilized to around 6 mmol/l by iv insulin infusion and hypoglycemia was induced by increasing the insulin infusion rate-in the night studies at 01.30, in the day studies at 08.00. Blood glucose nadirs were 1.5 +/- 0.4 (1.2-1.9) mmol/l at night and 1.9 +/- 0.3 (1.3-2.2) mmol/l during the day; in three patients the nadirs were identical during both the night and day. One patient had no adrenaline response to daytime hypoglycemia. In general, nocturnal hypoglycemia elicited greater catecholamine responses correlated to the duration of hypoglycemia. Glucagon responses showed a great heterogeneity independently of diabetes duration and hypoglycemic level. Growth hormone secretion was reduced during the night study; however, no refractory periods were found after sleep-related growth hormone secretion. In conclusion: counter-regulatory hormonal responses tend to be greater at night than during the day and do not explain why patients are not awakened by nocturnal hypoglycemia.