Decreased beta-adrenergic sensitivity in insulin-dependent diabetic subjects

To study beta-adrenergic sensitivity in diabetes mellitus, we performed isoproterenol sensitivity tests in 34 insulin-dependent diabetic patients and 10 age-matched normal subjects. beta-adrenergic sensitivity [defined as the dose of isoproterenol required to increase the resting heart rate by 25 beat/min, (I25)] was significantly higher in the diabetic group (4.07 +/- 1.4 micrograms, mean +/- SD) than in the normal group (2.02 +/- 1.49 micrograms). A comparison of I25 of normal subjects and diabetic patients as a function of age showed that the latter were significantly less sensitive to beta-adrenergic stimulation at all ages (P less than 0.01). In diabetic patients, beta-adrenergic sensitivity also increased with the duration of diabetes (r = 0.64, P less than 0.0005), but the correlation was stronger when the age of the patients and the duration of the diabetes were both taken into consideration (r = 0.72, P less than 0.0005). We conclude that beta-adrenergic sensitivity is diminished in patients with type I diabetes mellitus of all ages.