Growth hormone (GH) profiles with successive provocation by GH-releasing hormone and arginine in children: a clinical appraisal.

To establish a single and reliable test for evaluating growth hormone (GH) secretion, we examined successive GH provocation by two agents with different modes of action, GH releasinghormone (GHRH) and arginine (Arg) in 60 children of short stature, 6 patients with pituitary dwarfism and 9 normal young adults. Their GH profiles were qualitatively classified into 4 types: 25 children and 7 adults responded to both stimuli with 2 GH peaks (48.7±4.3 [SEM]μg/L for GHRH and 32.2±2.6μg/L for Arg in Children; 25.8±7.6μg/L and 30.1±9.2μg/L respectively in adults)(type A). A Single peak tor GHRH (57.7±4.6μg/L) without an Arg-induced peak was obtained in 29 younger children (type B), which is considered to be a GHRH-dominant pattern. Two of them were diagnosed as hypothalamic GHRH deficiency based on a low nocturnal plasma GH and good response to GH treatment. Six adolescents and 2 adults showed a blunted response to GHRH (9.0±1.1μg/L) but a normal response to Arg (40.6±9.5μg/L)(type C), which appears to be caused by somatostatin (SRIH) hypertonicity. None with pituitary dwarfism responded to both stimuli (4.5±1.3 and 2.3±0.5μg/L). Thus, the GHRH-Arg test makes it possible to evaluate the counterbalance between GHRH and SRIH as well as to differentiate pituitary GH deficiency from hypothalamic GHRH dysfunction.