title: Mechanism of impaired growth hormone secretion in patients with Cushing's disease.
abstract: The function of the growth hormone-releasing hormone (GHRH)-growth hormone (GH) axis in Cushing's disease was studied by monitoring (a) the GH responses to GHRH loading and L-dopa loading, (b) the GHRH response to L-dopa loading, and (c) the daytime profiles of plasma GH concentration. GH release following GHRH and L-dopa was blunted in patients as compared to that in age-matched control subjects. However, GHRH release following L-dopa was similar in patients and controls. The plasma GH levels in four patients measured every 20 min by a highly sensitive immunoradiometric assay for GH showed pulsatile GH secretion at low levels during the observation period. These results indicate that GHRH release from the hypothalamus is preserved in patients with Cushing's disease, and support the hypothesis that glucocorticoid inhibits GH secretion by altering the hypothalamic somatostatin tone.
authors.affiliation: First Department of Internal Medicine, School of Medicine, University of Tokushima, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Takahashi
authors.forename: H
authors.initials: H
authors.lastname: Bando
authors.forename: C
authors.initials: C
authors.lastname: Zhang
authors.forename: R
authors.initials: R
authors.lastname: Yamasaki
authors.forename: S
authors.initials: S
authors.lastname: Saito
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology; D003480:Cushing Syndrome / Q000097:blood*; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology; D013006:Growth Hormone / Q000097:blood*; D013007:Growth Hormone-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology; D006801:Humans; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D007275:Injections, Intravenous; D007980:Levodopa / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D011863:Radioimmunoassay
chemical_list: D005938:Glucocorticoids; D007980:Levodopa; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone