Direct effects of corticotrophin-releasing hormone on stimulated growth hormone secretion.
OBJECTIVE
This study evaluated the effect of corticotrophin-releasing hormone (CRH) on growth hormone releasing hormone (GHRH)-stimulated growth hormone (GH) release in man.


METHODS
Six healthy adult volunteers (age 20-35 years) were studied. On different occasions they each received an intravenous bolus of saline, CRH(1-41) (100 micrograms), adrenocorticotrophic hormone (ACTH) [Synacthen (500 ng/m2)] or hydrocortisone (50 mg), followed 30 minutes later by an intravenous bolus of either GHRH-(1-29)-NH2 (1.0 microgram/kg) or saline.


METHODS
Serum GH concentrations were measured using an immunoradiometric assay, and cortisol concentrations were measured by commercial radioimmunoassay. TSH concentrations were measured using a solid phase immunoradiometric assay kit.


RESULTS
Pretreatment with CRH(1-41) attenuated the GH response to GHRH [saline/GHRH-(1-29)-NH2 20.2 +/- 6.2 mU/l; CRH(1-41)/GHRH-(1-29)-NH2 10.9 +/- 2.8 mU/l (P = 0.01)]. This effect was not due to the rise in ACTH or cortisol induced by CRH(1-41), since pretreatment with either ACTH or hydrocortisone significantly augmented the GH response to GHRH-(1-29)-NH2 in the same subjects [ACTH/GHRH-(1-29)-NH2 30.3 +/- 8.8 mU/l (P = 0.01); hydrocortisone/GHRH-(1-29)-NH2 36.4 +/- 11.2 mU/l (P = 0.02)].


CONCLUSIONS
Our data suggest that the inhibitory effect of CRH(1-41) on GHRH-(1-29)-NH2-induced GH release is not a result of ACTH or cortisol release but reflects a direct action of CRH on GH secretion, possibly via stimulation of somatostatin release. The acute rise in GH following glucocorticoid administration could be explained in part by a rapid suppression of endogenous CRH.
Raza
J
J
London Centre for Paediatric Endocrinology and Metabolism, Middlesex Hospital, London, UK.
Massoud
A F
AF
Hindmarsh
P C
PC
Robinson
I C
IC
Brook
C G
CG
D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000494:pharmacology; D000328:Adult; D000704:Analysis of Variance; D019540:Area Under Curve; D003346:Corticotropin-Releasing Hormone; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood* / Q000494:pharmacology; D015592:Immunoradiometric Assay; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology*; D013268:Stimulation, Chemical; D013972:Thyrotropin / Q000097:blood
D010446:Peptide Fragments; D000324:Adrenocorticotropic Hormone; D013972:Thyrotropin; D013006:Growth Hormone; D003346:Corticotropin-Releasing Hormone; D013007:Growth Hormone-Releasing Hormone; C059148:somatotropin releasing hormone (1-29); D006854:Hydrocortisone