RETURN OF BETA-ADRENERGIC SENSITIVITY IN A PATIENT WITH INSULINOMA AFTER REMOVAL OF THE TUMOR

beta-Adrenergic sensitivity and counterregulatory hormone and symptoma tic responses to hypoglycaemia were studied in a 22-year-old man befor e and 3 and 34 weeks after removal of an insulinoma. The beta-adrenerg ic sensitivity was measured by the effect of an isoprenaline infusion on the heart rate, and the dose needed to increase the heart rate by 2 5 beats min(-1) (I-25) calculated from regression lines. The glucose t hresholds for the hormonal responses and symptoms were studied during a gradual fall in plasma glucose using a hypoglycaemic clamp technique . As compared with preoperative values, beta-adrenergic sensitivity wa s unchanged 3 weeks after surgery, but showed a marked improvement aft er 34 weeks, the I-25 (in pg isoprenaline) being 0.96, 0.86, and 0.56, respectively. The hormone responses to hypoglycaemia were earlier, bu t with no improvement in symptom generation at 3 weeks. After 34 weeks , the thresholds for both hormone release and symptom generation occur red at a plasma glucose approximately 1 mmol l(-1) higher than before surgery. Thus, in our patient, there was a marked improvement in beta- adrenergic sensitivity, an earlier release of counterregulatory hormon es, and an earlier recognition of hypoglycaemic symptoms after surgery . However, the restoration of these responses took more than 3 weeks. (C) 1997 by John Wiley & Sons, Ltd.