Ok I found this on the The Journal of Clinical Endorcrinology + Metabolism site. I'm not sure if I should put it here on on the HRT site.
Sustained Elevation of Pulsatile Growth Hormone (GH) Secretion and Insulin-Like Growth Factor I (IGF-I), IGF-Binding Protein-3 (IGFBP-3), and IGFBP-5 Concentrations during 30-Day Continuous Subcutaneous Infusion of GH-Releasing Peptide-2 in Older Men and Women
Cyril Y. Bowers, Ramona Granda, Subburaman Mohan, Jonathan Kuipers, David Baylink and Johannes D. Veldhuis
Tulane University Health Sciences Center (C.Y.B., R.G.), New Orleans, Louisiana 70112; Loma Linda University, J. L. Pettit Veterans Affairs Medical Center (S.M., D.B.), Loma Linda, California 92357; and Division of Endocrinology and Metabolism, Department of Internal Medicine, Mayo Medical and Graduate Schools, General Clinical Research Center, Mayo Clinic (J.K., J.D.V.), Rochester, Minnesota 55905
Address all correspondence and requests for reprints to: Dr. Cyril Y. Bowers, Tulane University Health Sciences Center, Box SL 53, New Orleans, Louisiana 70112. E-mail: rjabower{at}tulane.edu.
Abstract
We test the interlinked hypotheses that in healthy older adults: 1) iv injection of GH-releasing peptide-2 (GHRP-2) and GHRH synergizes more in aging women than men; 2) sc infusion of both GHRP-2 (1 μg/kg·h = 1) and GHRH (1, 3, or 10) for 24 h augments GH secretion more than either agonist alone; and 3) continuous sc delivery of GHRP-2 (1) for 30 d stimulates daily GH secretion and IGF-I, IGF-binding protein-3 (IGFBP-3), and IGFBP-5. Acute two-peptide synergy was 3-fold greater in young (n = 16) than older volunteers (n = 17; P < 0.025) and was 2.3-fold higher in elderly women than men (P < 0.025). The 24-h infusion of GHRP-2 (1) combined with GHRH (3 or 10) in men and with GHRH (10) in women drove GH secretion more than GHRH alone (P ≤ 0.024). In the entire cohort (n = 11), GHRP-2/GHRH (1/10) stimulated GH secretion more than either GHRP-2 (1; P = 0.021) or GHRH (10; P = 0.012). The 30-d delivery of GHRP-2 (1; n = 17 subjects): 1) stimulated pulsatile, rhythmic, and entropic GH secretion by more than 3-fold on d 1 and more than 1.8-fold on d 14 and 30 (each P < 0.001 vs. saline); 2) elevated IGF-I to a stable plateau on d 1, 14, and 30 (P < 0.025 vs. baseline); and 3) increased IGFBP-3 (P < 0.01) and IGFBP-5 (P < 0.025) on d 14 and/or 30. Safety screening tests remained normal. In summary, in healthy elderly women and men: 1) acute synergy of GHRP-2 and GHRH is greater in the female; 2) 24-h combined GHRP-2 and GHRH drive is more effective than either agonist alone; and 3) 30-d stimulation with GHRP-2 sustains a physiologically activated somatotropic axis. We conclude that age, gender, stimulus duration, and secretagogue combination determine acute, intermediate, and extended responses of the somatotropic axis in the older adult.
It appears that these peptides work better in younger men and women than older men. And it verifies that both GHRP- 2 and GHRH are more effective together. The study did not indicate at what doseage the test subjects were injected SC.