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Objective: Patients with childhood-onset GH deficiency (coGHD) need retesting in late adolescence or young adulthood to verify whether they need to continue GH treatment. For this purpose the Growth Hormone Research Society (GRS) recommends the insulin tolerance test (ITT), or as an alternative the arginine + growth hormone releasing hormone test (ARG + GHRH test) as a diagnostic tool in adolescents and adults. However, there are no standardized cut-off levels based on normal GH secretion for determining GHD vs. GH sufficiency in young adults for the ITT, the ARG + GHRH test or the pyridostigmine + GHRH (PD + GHRH) test, a further new GH stimulation test., Patients and Measurements: We studied 43 patients (28 with organic coGHD, 15 with idiopathic coGHD; 30 males, 13 females; aged 20.4 years, range 16.2-25.4; body mass index 23.5, range 16.3-35.8) using the ARG [0.5 g/kg intravenously (i.v.)] + GHRH (1 micro g/kg i.v.) test, the PD (120 mg orally) + GHRH (1 micro g/kg i.v.) test and the ITT (0.1 IU/kg i.v.) and compared these data with the results of 40 healthy age- and weight-matched volunteers., Results: The GH response in patients was significantly lower than in healthy controls: ARG + GHRH test, 0.8 micro g/l (interquartile range 0.3-2.6) vs. 51.8 micro g/l (32.6-71.2) in controls (P < 0.0001); PD + GHRH test, 0.9 micro g/l (0.3-1.9) vs. 40.4 micro g/l (27.1-54.4) in controls (P < 0.0001); ITT, 0.1 micro g/l (0.0-0.8) vs. 20.3 micro g/l (14.7-31.7) in controls (P < 0.0001). In the ARG + GHRH test we found a diagnostic sensitivity of 100% and a specificity of 97.5% for a cut-off range from 15.1 to 20.3 micro g/l, in the PD + GHRH test a sensitivity of 100% and a specificity of 97% (cut-off range 9.1-13.1 micro g/l) and in the ITT a sensitivity and specificity of 100% each within a cut-off range from 2.7 to 8.8 micro g/l., Conclusion: There were no marked differences in sensitivity and specificity in young adults among ARG + GHRH test, PD + GHRH test and the ITT in assessing GH secretion. Because of the lack of side-effects, the ARG + GHRH test is the recommended method for re-evaluation of coGHD in young adults when pituitary GHD is suspected. Furthermore, in adult patient groups where organic pituitary coGHD is common, the ITT may be completely replaced by the ARG + GHRH test. Because of the predominance of hypothalamic GHD in childhood, the ITT is commonly performed for the re-evaluation of patients with childhood-onset GHD because of its mechanism of GH stimulation. The present results confirm the high discriminatory capability of the ITT in young adults.

Background/method: We compared the growth hormone response to a modified exercise test--the treadmill exhausting test--to pharmacological stimulation tests in 77 children with short stature. Each child underwent the treadmill test to individual exhaustion and at least one pharmacological test for GH stimulation. To determine the point of individual exhaustion, the heart rate, workload and oxygen consumption were measured., Results: The mean +/- SEM peak GH concentration (ng/ml) in 47 small, normally growing children (group 1) was 16.1 +/- 1.3 in the pharmacological tests vs. 5.0 +/- 0.6 after a treadmill exhausting test. Thirty children with GH deficiency (group 2) had mean +/- SEM peak GH concentrations (ng/ml) of 5.5 +/- 0.5 in the pharmacological tests and 4.1 +/- 0.7 after physical exercise. The groups differed significantly in the pharmacological tests (p < 0.001) but not in the exhausting test. We found a 90% sensitivity but only a 11% specificity for the treadmill exhausting test compared to the diagnosis obtained by pharmacological testing., Conclusion: We do not recommend the treadmill exhausting test in clinical practice of pediatric endocrinology at all., (Copyright 2001 S. Karger AG, Basel)