Propranolol-augmented, exercise-induced human growth hormone release.

Serum growth hormone (HGH) responses to 20 minutes of exercise 90 minutes after orally given propranolol (0.5 mg/kg; maximum, 40 mg), were assessed in 15 short but otherwise normal children, in 2 obese teen-agers, in 3 hypopituitary children, and in 8 healthy adult volunteers. In six adults HGH responses to exercise alone were also assessed one week previously. Normal children responded with a peak serum HGH concentration of 10 ng/ml or greater, except one whose peak was 7 ng/ml (normal, greater than 7 ng/ml). The obese girls showed smaller responses to exercise with propranolol (ex/prop) (peak HGH, 6 ng/ml), to hypoglycemia, and to levodopa (peak HGH, 7 and 4 ng/ml). The three hypopituitary children did not respond to ex/prop or to two other stimuli. In the volunteer adults, the mean HGH responses were greater to ex/prop than to exercise alone, although two out of six did not have increased levels with exercise. There were also elevations of fasting serum HGH levels before exercise and propranolol on repeat testing. These results suggest that orally given propranolol improves the exercise-HGH stimulation test both in the number of responders and in the degree of response. Some individuals have an anticipatory HGH secretion before exercise due to a conditioned response.