Comparison of growth hormone-releasing effect of growth hormone-releasing hormone, clonidine and pyridostigmine in normal children and adolescents. GH-releasing effect of GHRH, clonidine and pyridostigmine.
The GHRH test has been proposed to replace conventional stimuli in the diagnosis of GH deficiency. However the reliability of GHRH in discriminating between normal and GH-deficient children is still uncertain. The aim of this study was to compare the GH-releasing effect of GHRH (1 microgram/kg i.v.) with that of two neuroactive drugs, clonidine (CLON, 150 micrograms/m2 orally), an alpha 2-receptor agonist, and pyridostigmine (PD, 60 mg orally), a cholinergic agonist that inhibits cholinesterases, in 23 children and adolescents with normal and familial short stature. The plasma GH peak (mean +/- SEM) after GHRH (20.3 +/- 2.5 ng/ml), CLON (17.0 +/- 2.1 ng/ml) and PD (14.9 +/- 1.5 ng/ml) did not significantly differ. According to the conventional limit (less than 10 ng/ml), a false negative response was present in 6, 5 and 6 subjects after GHRH, CLON and PD, respectively. In conclusion, GHRH, CLON and PD have a similar GH-releasing effect. A similar percentage of false negative responses was observed with all tests and this evidence reduces their diagnostic ability.