title: Acute clonidine administration potentiates spontaneous diurnal, but not nocturnal, growth hormone secretion in normal short children.
abstract: It has been shown that alpha 2-adrenoreceptor activation induced by clonidine (CLON) increases plasma GH levels in both adults and children. In this study the effects of CLON (150 micrograms/m2, orally) on GH secretion were studied both in the morning (from 0800-1100 h) and at night (from 2300-0200 h) in nine short children previously shown to have normal spontaneous nocturnal GH secretion. In the morning, CLON induced a GH increase higher than placebo [peak (mean +/- SEM), 23.8 +/- 4.3 vs. 3.4 +/- 1.4 micrograms/L; P = 0.0001; area under curve (AUC), 624.4 +/- 62.7 vs. 135.6 +/- 33.3 micrograms/L.h; P less than 0.00001]. In the night, no difference was observed between GH secretion after CLON (peak, 15.4 +/- 3.2 micrograms/L; AUC, 562.2 +/- 57.5 micrograms/L.h) and placebo (peak, 13.1 +/- 4.7 micrograms/L; AUC, 497.2 +/- 83.5 micrograms/L.h). Spontaneous GH secretion was higher during the night than in the morning (P = 0.0001), whereas nocturnal GH secretion overlapped with that in the morning after CLON. The data presented show that alpha 2-adrenoreceptor activation is probably mediated by increased endogenous GHRH release; our results suggest that the endogenous GHRH secretion is maximally stimulated at night.
authors.affiliation: Department of Clinical Physiopathology, University of Turin, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Ghigo
authors.forename: E
authors.initials: E
authors.lastname: Arvat
authors.forename: M
authors.initials: M
authors.lastname: Nicolosi
authors.forename: J
authors.initials: J
authors.lastname: Bellone
authors.forename: M R
authors.initials: MR
authors.lastname: Valetto
authors.forename: E
authors.initials: E
authors.lastname: Mazza
authors.forename: E
authors.initials: E
authors.lastname: Imperiale
authors.forename: M
authors.initials: M
authors.lastname: Procopio
authors.forename: M C
authors.initials: MC
authors.lastname: Ghigo
authors.forename: F
authors.initials: F
authors.lastname: Camanni
mesh_terms: D000293:Adolescent; D001827:Body Height; D002648:Child; D002940:Circadian Rhythm; D003000:Clonidine / Q000494:pharmacology*; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D006801:Humans; D008297:Male; D010919:Placebos; D012016:Reference Values
chemical_list: D010919:Placebos; D013006:Growth Hormone; D003000:Clonidine