A five day treatment with daily subcutaneous injections of growth hormone-releasing peptide-2 causes response attenuation and does not stimulate insulin-like growth factor-I secretion in healthy young men.
Nijland. E A EA; Strasburger. C J CJ; Popp-Snijders. C C; van der Wal. P S PS; van der Veen. E A EA
Key Findings
- GH peaks dropped from ~83 µg/L on day 1 to ~51 µg/L on day 5, showing rapid response attenuation.
- Serum IGF‑I levels stayed unchanged over the 5‑day period despite continued GH release.
- Osteocalcin, a marker of GH activity in tissue, increased significantly, indicating some peripheral GH effect.
Practical Outcomes
- Short‑term daily GHRP‑2 can boost GH but quickly loses potency and doesn’t raise IGF‑I, so it’s unlikely to provide the long‑term anabolic or anti‑aging benefits many biohackers seek. If using GHRP‑2, consider cycling (e.g., intermittent days or weeks off) to avoid tolerance, and don’t expect rapid IGF‑I increases. Monitoring bone turnover markers may be useful, but the main takeaway is that continuous daily dosing for more than a few days offers diminishing returns.
Summary
In a small study of nine healthy young men, daily injections of 100 µg GHRP‑2 for five days kept releasing growth hormone, but the hormone spikes got smaller each day. After five days there was no rise in the blood level of IGF‑I (the downstream hormone linked to many anti‑aging claims), although a bone‑related marker called osteocalcin did go up.
Abstract
The synthetic hexapeptide growth hormone-releasing peptide (GHRP)-2 specifically stimulates GH release in man. To determine the effects of prolonged treatment and whether response attenuation occurs in man, we administered to nine healthy subjects a daily s.c. injection of 100 microg GHRP-2 over 5 days. Every day blood samples were taken to determine GH, IGF-I, IGF-binding protein (IGFBP)-3 and osteocalcin levels. On days 1,3 and 5, GH was measured at -20,0,20,40,60,90,120 and 180 min using an immunometric and an immunofunctional assay. Mean-/+S.D). peak GH concentrations were 83+/-31, 59+/-22 and 51+/-13 microg/l on days 1, 3 and 5 respectively. Mean+/-S.D. areas under the curve for days 1, 3 and 5 were 6366+/-2514, 3987 +/- 1418 and 3392+/-1215 mU/l per min. Despite the maintained GH release, analysis of variance revealed that significant response attenuation occurred (P < 0.01). Mean serum IGF-I concentration did not increase after a 5 day treatment with GHRP-2. Mean basal levels were 22, 25,23,25,23,24 nmol/l measured on days 1 to 6. However, osteocalcin, another serum marker of GH activity in tissue, increased significantly from 3.2+/-1.0 to 4.2+/-0.4 microg/l (mean+S.D.) (P< 0.01).
Study Information
pubmed
1998
10.1530/eje.0.1390395