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 releasing-hormone (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] micrograms/L for GHRH and 32.2 +/- 2.6 micrograms/L for Arg in children; 25.8 +/- 7.6 micrograms/L and 30.1 +/- 9.2 micrograms/L respectively in adults) (type A). A single peak for GHRH (57.7 +/- 4.6 micrograms/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 +/- 1.1 micrograms/L) but a normal response to Arg (40.6 +/- 9.5 micrograms/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 +/- 0.5 micrograms/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.