Growth hormone-releasing peptide-2 infusion synchronizes growth hormone, thyrotrophin and prolactin release in prolonged critical illness.
OBJECTIVE
During prolonged critical illness, nocturnal pulsatile secretion of GH, TSH and prolactin (PRL) is uniformly reduced but remains responsive to the continuous infusion of GH secretagogues and TRH. Whether such (pertinent) secretagogues would synchronize pituitary secretion of GH, TSH and/or PRL is not known.


METHODS
We explored temporal coupling among GH, TSH and PRL release by calculating cross-correlation among GH, TSH and PRL serum concentration profiles in 86 time series obtained from prolonged critically ill patients by nocturnal blood sampling every 20 min for 9 h during 21-h infusions of either placebo (n=22), GHRH (1 microg/kg/h; n=10), GH-releasing peptide-2 (GHRP-2; 1 microg/kg/h; n=28), TRH (1 microg/kg/h; n=8) or combinations of these agonists (n=8).


RESULTS
The normal synchrony among GH, TSH and PRL was absent during placebo delivery. Infusion of GHRP-2, but not GHRH or TRH, markedly synchronized serum profiles of GH, TSH and PRL (all P< or =0.007). After addition of GHRH and TRH to the infusion of GHRP-2, only the synchrony between GH and PRL was maintained (P=0.003 for GHRH + GHRP-2 and P=0.006 for TRH + GHRH + GHRP-2), and was more marked than with GHRP-2 infusion alone (P=0.0006 by ANOVA).


CONCLUSIONS
The nocturnal GH, TSH and PRL secretory patterns during prolonged critical illness are herewith further characterized to include loss of synchrony among GH, TSH and PRL release. The synchronizing effect of an exogenous GHRP-2 drive, but not of GHRH or TRH, suggests that the presumed endogenous GHRP-like ligand may participate in the orchestration of coordinated anterior pituitary hormone release.
Department of Intensive Care Medicine, University Hospital Gasthuisberg, University of Leuven, Belgium.
G
G
Van den Berghe
P
P
Wouters
C Y
CY
Bowers
F
F
de Zegher
R
R
Bouillon
J D
JD
Veldhuis
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003422:Critical Care; D004338:Drug Combinations; D013006:Growth Hormone / Q000097:blood*; D013007:Growth Hormone-Releasing Hormone / Q000008:administration & dosage / Q000627:therapeutic use; D006728:Hormones / Q000627:therapeutic use*; D006801:Humans; D007262:Infusions, Intravenous; D008875:Middle Aged; D009842:Oligopeptides / Q000008:administration & dosage / Q000627:therapeutic use*; D011388:Prolactin / Q000097:blood*; D013972:Thyrotropin / Q000008:administration & dosage / Q000097:blood* / Q000627:therapeutic use
D004338:Drug Combinations; D006728:Hormones; D009842:Oligopeptides; D011388:Prolactin; D013972:Thyrotropin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; C091874:growth hormone-releasing peptide-2