TY - JOUR
T1 - Estradiol Supplementation Enhances Submaximal Feed-Forward Drive of Growth Hormone (GH) Secretion by Recombinant Human GH-Releasing Hormone-1,44-Amide in a Putatively Somatostatin-Withdrawn Milieu
AU - Veldhuis, Johannes D.
AU - Evans, William S.
AU - Bowers, Cyril Y.
PY - 2003/11
Y1 - 2003/11
N2 - To test the clinical hypothesis that an estrogen-enriched milieu enhances GHRH action, we administered placebo (Pl) and estradiol-17β (E 2) orally for 23 d to six postmenopausal women in a prospectively randomized, double-masked, within-subject crossover design with 6 wk intervening. The GHRH stimulation protocol entailed consecutive iv infusion of L-arginine and a single iv pulse of saline or one of five randomly ordered doses of recombinant human GHRH-1,44-amide (0.03, 0.1, 0.3, 1.0, or 3.0 μg/kg) in a total of 12 separate morning, fasting sessions. GH secretion was monitored by sampling blood every 10 min for 6 h; chemiluminescence assay of GH concentrations; deconvolution analysis of stimulated GH release; and nonlinear dose-response reconstruction. Supplementation with E2, compared with Pl:1) increased (mean ± SEM) E2 concentrations from 18 ± 3 (Pl) to 164 ± 12 pg/ml (to convert to picomoles per liter, multiply by 3.57) (P < 0.001); 2) decreased IGF-I concentrations from 181 ± 14 to 120 ± 11 μg/liter (P < 0.01); 3) elevated mean GH concentrations from 0.27 ± 0.06 to 0.59 ± 0.08 μg/liter (P = 0.014); 4) potentiated GH secretion stimulated by L-arginine alone by 1.43-fold (P = 0.012); 5) reduced the ED50 of GHRH from 0.27 ± 0.02 to 0.13 ± 0.01 μg/kg (P < 0.01), denoting enhanced GHRH potency; and 6) heightened the maximal slope of the dose-response function from 1.1 ± 0.1 to 1.4 ± 0.05 [(μg/liter) (μg/kg)-1] (P < 0.05), signifying augmented pituitary sensitivity. The foregoing facilitative mechanisms were specific because E2 replacement did alter maximal L-arginine/GHRH-induced GH secretion, indicating unchanged secretagogue efficacy. In conclusion, inasmuch as E2 also attenuates inhibition of GH secretion by infused somatostatin and potentiates stimulation of GH secretion by GH-releasing peptide-2, we postulate that estrogenic steroids drive pulsatile GH production in part via mechanisms that include all three of GHRH, somatostatin, and putatively GH-releasing peptide/ghrelin signaling.
AB - To test the clinical hypothesis that an estrogen-enriched milieu enhances GHRH action, we administered placebo (Pl) and estradiol-17β (E 2) orally for 23 d to six postmenopausal women in a prospectively randomized, double-masked, within-subject crossover design with 6 wk intervening. The GHRH stimulation protocol entailed consecutive iv infusion of L-arginine and a single iv pulse of saline or one of five randomly ordered doses of recombinant human GHRH-1,44-amide (0.03, 0.1, 0.3, 1.0, or 3.0 μg/kg) in a total of 12 separate morning, fasting sessions. GH secretion was monitored by sampling blood every 10 min for 6 h; chemiluminescence assay of GH concentrations; deconvolution analysis of stimulated GH release; and nonlinear dose-response reconstruction. Supplementation with E2, compared with Pl:1) increased (mean ± SEM) E2 concentrations from 18 ± 3 (Pl) to 164 ± 12 pg/ml (to convert to picomoles per liter, multiply by 3.57) (P < 0.001); 2) decreased IGF-I concentrations from 181 ± 14 to 120 ± 11 μg/liter (P < 0.01); 3) elevated mean GH concentrations from 0.27 ± 0.06 to 0.59 ± 0.08 μg/liter (P = 0.014); 4) potentiated GH secretion stimulated by L-arginine alone by 1.43-fold (P = 0.012); 5) reduced the ED50 of GHRH from 0.27 ± 0.02 to 0.13 ± 0.01 μg/kg (P < 0.01), denoting enhanced GHRH potency; and 6) heightened the maximal slope of the dose-response function from 1.1 ± 0.1 to 1.4 ± 0.05 [(μg/liter) (μg/kg)-1] (P < 0.05), signifying augmented pituitary sensitivity. The foregoing facilitative mechanisms were specific because E2 replacement did alter maximal L-arginine/GHRH-induced GH secretion, indicating unchanged secretagogue efficacy. In conclusion, inasmuch as E2 also attenuates inhibition of GH secretion by infused somatostatin and potentiates stimulation of GH secretion by GH-releasing peptide-2, we postulate that estrogenic steroids drive pulsatile GH production in part via mechanisms that include all three of GHRH, somatostatin, and putatively GH-releasing peptide/ghrelin signaling.
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U2 - 10.1210/jc.2003-030410
DO - 10.1210/jc.2003-030410
M3 - Article
C2 - 14602794
AN - SCOPUS:0344011123
SN - 0021-972X
VL - 88
SP - 5484
EP - 5489
JO - Journal of Clinical Endocrinology and Metabolism
JF - Journal of Clinical Endocrinology and Metabolism
IS - 11
ER -