PLASMA-CATECHOLAMINE RESPONSES TO HYPOGLYCEMIA IN CHILDREN AND ADOLESCENTS WITH IDDM

The goal of this study was to assess whether children and adolescents with insulin-dependent diabetes mellitus (IDDM) have decreased catecholamine responses to insulin-induced hypoglycemia as has been reported in adults and to explore the pathogenesis of the decreased response in terms of possible relationships to autonomic neuropathy or hyperinsulinism. Research Design and Methods: A before-and-after trial on the effects of 3 days of intensive insulin therapy was conducted on 60 subjects with IDDM (age 15.4 +/- 2.6 yr, duration of diabetes 7.8 +/- 3.5 yr). The control group consisted of 5 children with non-growth hormone-deficient short stature (age 14.8 +/- 3.2 yr). Hypoglycemia was induced with an intravenous insulin bolus (0.15-0.75 U/kg) after insulin withdrawal and 3 days of intensive insulin therapy in diabetic subjects on an inpatient basis to assess the role of hyperinsulinism in suppressing the catecholamine response to hypoglycemia. Control subjects were studied once and received an insulin bolus of 0.1-mu-U/kg. Autonomic neuropathy was assessed by computerized assessment of the basal R-R variation during inspiration and expiration and the pancreatic polypeptide response to hypoglycemia. Results: Basal plasma catecholamine levels were lower in diabetic subjects after intensive insulin therapy than in control subjects (P = 0.008). The peak and incremental catecholamine responses after insulin withdrawal and intensive insulin therapy in IDDM subjects were significantly decreased compared with control subjects (P < 0.001). Peak catecholamine responses to hypoglycemia in IDDM were decreased after intensive insulin therapy (P = 0.002). This was particularly true in those with plasma glucose nadir levels of < 2.2 mmol (P < 0.001). The diminished catecholamine responses were primarily due to decreased peak epinephrine responses after intensive insulin therapy compared with insulin withdrawal (P = 0.011). There were no significant correlations between the catecholamine response to hypoglycemia and age, duration of diabetes, pancreatic polypeptide, or R-R interval. Conclusions: These results suggest that children and adolescents with IDDM after insulin withdrawal have diminished catecholamine response to hypoglycemia compared with control subjects and indicate that short-term intensive insulin therapy diminishes this response further. Thus, hyperinsulinism may play a role in suppressing the catecholamine response to hypoglycemia. There is no evidence for a clinical or subclinical role of autonomic neuropathy to explain the altered catecholamine responses.