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.
Bowers. Cyril Y CY; Granda. Ramona R; Mohan. Subburaman S; Kuipers. Jonathan J; Baylink. David D; Veldhuis. Johannes D JD
Key Findings
- Acute co‑administration of GHRP‑2 and GHRH boosts GH release more than either peptide alone, with a stronger effect in older women.
- A 24‑hour infusion of GHRP‑2 plus GHRH produces higher GH output than GHRH alone.
- Continuous 30‑day sub‑cutaneous infusion of GHRP‑2 alone raises pulsatile GH secretion 1.8‑3‑fold and sustains higher IGF‑I, IGFBP‑3, and IGFBP‑5 levels, with no adverse lab changes.
Practical Outcomes
- For biohackers, the data suggest that a steady low‑dose infusion of GHRP‑2 can maintain an activated somatotropic axis in older adults, but it requires an infusion pump and careful dosing. Combining GHRP‑2 with GHRH may give a stronger short‑term GH boost, especially for women. The study provides reassuring safety signals for prolonged low‑dose use, though the delivery method may limit everyday practicality.
Summary
In healthy older men and women, a 30‑day continuous sub‑cutaneous infusion of the peptide GHRP‑2 at a low dose (about 1 µg per kg body weight per hour) kept growth hormone pulses high and raised IGF‑I and its binding proteins, without any safety problems. The study also showed that giving GHRP‑2 together with GHRH works better than either alone, especially in older women.
Abstract
We test the interlinked hypotheses that in healthy older adults: 1). i.v. 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 microg/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 <or= 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.
Study Information
pubmed
2004
10.1210/jc.2003-031799