Document Detail

Pulsatile and nocturnal growth hormone secretions in men do not require periodic declines of somatostatin.
MedLine Citation:
PMID:  12670836     Owner:  NLM     Status:  MEDLINE    
Using a continuous subcutaneous octreotide infusion to create constant supraphysiological somatostatinergic tone, we have previously shown that growth hormone (GH) pulse generation in women is independent of endogenous somatostatin (SRIH) declines. Generalization of these results to men is problematic, because GH regulation is sexually dimorphic. We have therefore studied nine healthy young men (age 26 +/- 6 yr, body mass index 23.3 +/- 1.2 kg/m2) during normal saline and octreotide infusion (8.4 microg/h) that provided stable plasma octreotide levels (764.5 +/- 11.6 pg/ml). GH was measured in blood samples obtained every 10 min for 24 h. Octreotide suppressed 24-h mean GH by 52 +/- 13% (P = 0.016), GH pulse amplitude by 47 +/- 12% (P = 0.012), and trough GH by 39 +/- 12% (P = 0.030), whereas GH pulse frequency and the diurnal rhythm of GH secretion remained essentially unchanged. The response of GH to GH-releasing hormone (GHRH) was suppressed by 38 +/- 15% (P = 0.012), but the GH response to GH-releasing peptide-2 was unaffected. We conclude that, in men as in women, declines in hypothalamic SRIH secretion are not required for pulse generation and are not the cause of the nocturnal augmentation of GH secretion. We propose that GH pulses are driven primarily by GHRH, whereas ghrelin might be responsible for the diurnal rhythm of GH.
Eleni V Dimaraki; Craig A Jaffe; Cyril Y Bowers; Peter Marbach; Ariel L Barkan
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.     Date:  2003-04-01
Journal Detail:
Title:  American journal of physiology. Endocrinology and metabolism     Volume:  285     ISSN:  0193-1849     ISO Abbreviation:  Am. J. Physiol. Endocrinol. Metab.     Publication Date:  2003 Jul 
Date Detail:
Created Date:  2003-06-06     Completed Date:  2003-07-18     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  100901226     Medline TA:  Am J Physiol Endocrinol Metab     Country:  United States    
Other Details:
Languages:  eng     Pagination:  E163-70     Citation Subset:  IM    
Department of Internal Medicine, Division of Endocrinology and Metabolism, University of Michigan, Ann Arbor 48109, USA.
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MeSH Terms
Circadian Rhythm / physiology*
Growth Hormone-Releasing Hormone / pharmacology
Hormones / administration & dosage,  pharmacokinetics,  pharmacology
Human Growth Hormone / blood*
Infusions, Intravenous
Octreotide / administration & dosage,  pharmacokinetics,  pharmacology
Oligopeptides / pharmacology
Somatostatin / blood*,  physiology
Grant Support
Reg. No./Substance:
0/Hormones; 0/Oligopeptides; 0/growth hormone-releasing peptide-2; 12629-01-5/Human Growth Hormone; 51110-01-1/Somatostatin; 83150-76-9/Octreotide; 9034-39-3/Growth Hormone-Releasing Hormone

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