Twenty-four hour continuous ghrelin infusion augments physiologically pulsatile, nycthemeral, and entropic (feedback-regulated) modes of growth hormone secretion.
J Clin Endocrinol Metab
; 93(9): 3597-603, 2008 Sep.
Article
in En
| MEDLINE
| ID: mdl-18593763
ABSTRACT
BACKGROUND:
Ghrelin is a 28-amino acid acylated peptide that potentiates GHRH stimulation and opposes somatostatin inhibition acutely. Whether prolonged ghrelin administration can sustain physiological patterns of GH secretion remains unknown.HYPOTHESIS:
Continuous delivery of ghrelin will amplify physiological patterns of GH secretion over 24 h.SUBJECTS:
Men and women ages 29-69 yr, body mass indices 23-52 kg/m2, were included in the study. LOCATION The study was performed at an academic medical center.METHODS:
Twenty-four hour continuous sc infusion of saline vs. ghrelin (1 microg/kg.h) with frequent sampling was examined. Deconvolution and entropy analyses were performed.OUTCOMES:
IGF-I concentrations were determined. Basal, pulsatile, nycthemeral, and entropic measures of GH secretion were calculated.RESULTS:
Ghrelin infusion compared with saline infusion for 24 h elevated (median) acylated ghrelin, GH, and IGF-I concentrations by 8.1-fold (P < 0.001),11-fold (P < 0.001), and 1.4-fold (P = 0.002). GH secretory-burst mass and frequency increased by 6.6-fold (P = 0.004) and 1.7-fold (P < 0.001), respectively, resulting in a 12-fold increase in pulsatile GH secretion (P < 0.001). Interpulse variability decreased significantly (P = 0.046), whereas GH secretory-burst shape and half-life did not change. The amplitude of the nycthemeral GH rhythm increased by 3.4-fold (P < 0.001), and GH patterns became more irregular (higher approximate entropy P < 0.001). Combining GHRH with ghrelin was not an additive in driving GH secretion.CONCLUSIONS:
Continuous ghrelin infusion for 24 h elevates acylated ghrelin, GH and IGF-I concentrations, and stimulates pulsatile, nycthemeral, and entropic modes of GH secretion. The consistency of outcomes in a heterogeneous cohort of adults suggests potentially broad utility of this physiological secretagogue in hyposomatotropic states.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Pulsatile Flow
/
Circadian Rhythm
/
Human Growth Hormone
/
Feedback, Physiological
/
Ghrelin
Limits:
Adult
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Aged
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Female
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Humans
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Male
/
Middle aged
Language:
En
Journal:
J Clin Endocrinol Metab
Year:
2008
Document type:
Article
Affiliation country:
Estados Unidos
Publication country:
EEUU
/
ESTADOS UNIDOS
/
ESTADOS UNIDOS DA AMERICA
/
EUA
/
UNITED STATES
/
UNITED STATES OF AMERICA
/
US
/
USA