Hypoglycemic symptoms and decreased beta-adrenergic sensitivity in insulin-dependent diabetic patients

Thirty-seven insulin-dependent diabetic patients were tested for symptoms of hypoglycemia, cardiac autonomic neuropathy (i.e., heart rate variation during deep breathing, Valsalva maneuver, immediate heart rate response to standing), and isoproterenol sensitivity (defined as the dose of isoproterenol required to increase heart rate by 25 beats/min: I25). Tests of cardiac autonomic neuropathy showed no relation to hypoglycemic symptoms. On the contrary, a clear relationship could be established between isoproterenol sensitivity and adrenergic symptoms of hypoglycemia. Diabetic patients with decreased response to isoproterenol had fewer adrenergic symptoms, perceived hypoglycemia at a lower blood glucose level, and had more hypoglycemic accidents. Symptoms most related to isoproterenol sensitivity were tremor, sweaty palms, and hunger. With the isoproterenol-sensitivity test a distinction could be made between the groups at high (I25 greater than 3 micrograms) and low (I25 less than 3 micrograms) risk for hypoglycemic accidents. We suggest that the isoproterenol-sensitivity test could be used to identify diabetic patients at increased risk for hypoglycemia.