HUMAN GROWTH HORMONE (hGH) STIMULATION TESTS: THE SEQUENTIAL EXERCISE AND l-DOPA PROCEDURE

Abstract

Forty eight normal volunteers, 13 subjects with short stature without apparent cause and 31 patients with delayed growth clinically highly suggestive of growth hormone deficiency (GHD), with chronological ages of 11.4 .+-. 0.4 yrs (mean .+-. SE), 14.0 .+-. 0.7 and 12.8 .+-. 0.8 yr; height age of 11.0 .+-. 0.4, 8.9 .+-. 0.7 and 6.3 .+-. 0.4 yr and bone age of 10.7 .+-. 0.7, 9.9 .+-. 0.8 and 7.5 .+-. 0.7 yr, respectively, were tested with provocative tests of hGH release (insulin-induced hypoglycemia, Arg infusion, L-DOPA, exercise and sequential exercise and L-DOPA) to identify GHh deficiency. In the normal subjects (control plus short stature) the sequential exercise and L-DOPA test induced the greatest peak and integrated secretion rates of plasma hGH (16.5 .+-. 1.2 ng/ml and 679 .+-. 70 ng/ml per 120 min, respectively) when compared to other tests. This combined stimulus was the only one to which all normal subjects responded; a similar degree of responsiveness has not been earlier described for other hGH-stimuli. The responses observed with all stimuli were significantly lower (P < 0.001) in GHD group compared to the normal subjects. Emphasis was given to the sequential exercise and L-DOPA test as an innocuous, sensitive and simplified procedure in the evaluation of children with growth retardation.