WEAK RELATIONSHIP BETWEEN SYMPTOM PERCEPTION AND OBJECTIVE HYPOGLYCEMIA-INDUCED CHANGES OF AUTONOMIC FUNCTION IN HYPOGLYCEMIA UNAWARENESS IN DIABETES

To assess the relationship between symptom perception and neurophysiol ogical characteristics in hypoglycaemia unawareness, we investigated t he awareness of symptoms, objective changes of autonomic function and counter-regulatory neuroendocrine responses to hypoglycaemia in intens ively treated type I (insulin-dependent) diabetic patients with differ ent degrees of hypoglycaemia unawareness. Hypoglycaemia (venous plasma glucose below 2.2 mmol/l) was induced with an intravenous insulin bol us in subjects with a history of repeated severe hypoglycaemia and hyp oglycaemia unawareness (n=10) and in a comparable group with good awar eness of hypoglycaemia (n=8). Autonomic symptoms, selected parameters of autonomic function and counter-regulatory hormones were assessed se rially. Although hypoglycaemia was more pronounced in unaware patients (1.6 vs 2.0 mmol/l, P=0.05), their induced adrenaline response was ma rkedly impaired (delta adrenaline: 1.25+/-1.10 vs 2.55+/-1.46 nmol/l, P=0.05). Astonishingly, differences between both patient groups in the course of autonomic function changes did not reach the level of signi ficance (P=0.35-0.92), although the unaware group reported markedly fe wer autonomic symptoms, both neurogenic (P=0.001) and neuroglycopenic (P=0.04) than the aware group. This study indicates that in hypoglycae mia unawareness even extensive changes in autonomic function are not s ufficient for the perception of hypoglycaemia and confirms that the ce ntral nervous system plays an important role in the awareness of hypog lycaemia.