REDUCED SENSITIVITY TO BETA-ADRENOCEPTOR STIMULATION AND BLOCKADE IN INSULIN-DEPENDENT DIABETIC-PATIENTS WITH HYPOGLYCEMIA UNAWARENESS

1 Nine IDDM-patients with hypoglycaemia unawareness, seven IDDM-patien ts withhypoglycemia awareness and a control group of nine healthy pers ons were included in this study. The patients were recruited from the medical out-patients' department of the University Hospital of Tromso. 2 The pathophysiological changes which cause hypoglycaemia unawarenes s are today not clear. Reduced peripheral tissue sensitivity to catech olamines is suggested as one of several mechanisms which may contribut e. 3 For further investigation of beta-adrenergic sensitivity an isopr enaline/metoprolol sensitivity test was performed. Isoprenaline and me toprolol were administered intravenously, and the effects on heart rat e (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP) and plasma levels of adrenaline (ADR) and noradrenaline (NA) were meas ured. All subjects were given the same doses of isoprenaline (0.25-8 m u g) and metoprolol (0.5-8 mg). Metoprolol was given together with the dose of isoprenaline which increased heart rate by 25 beats min(-1) 4 The dose/response curves of both isoprenaline/HR and metoprolol/HR we re significantly shifted to the right in IDDM-patients with hypoglycae mia unawareness compared with controls and IDDM-patients with hypoglyc aemia awareness (P < 0.05). 5 Reduced sensitivity of isoprenaline stim ulation has also been shown before, whereas reduced sensitivity of a b locking agent has not earlier been shown. 6 These findings support the hypothesis of reduced beta -adrenergic sensitivity as one pathophysio logical component in hypoglycaemia unawareness. Nine IDDM-patients wit h hypoglycaemia unawareness, seven IDDM-patients with