GHRP-6
Growth Hormone Releasing Peptide-6, Growth hormone-releasing hexapeptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2
Acute growth hormone (GH) response to GH-releasing hexapeptide in humans is independent of endogenous GH-releasing hormone.
Robinson. B M BM; Friberg. R D RD; Bowers. C Y CY; Barkan. A L AL
Key Findings
- GHRP‑6 induces an acute GH surge independent of endogenous GHRH.
- When the GHRH pathway is desensitized by continuous GHRH infusion, GHRP‑6 still elicits a robust GH response.
- The GH response to a bolus of GHRP‑6 (1 µg/kg) is comparable to that of a GHRH bolus in a normal state.
Practical Outcomes
- For biohackers, this means GHRP‑6 can be used to reliably boost GH even if other GH‑stimulating strategies (like GHRH peptides) are ineffective or down‑regulated. It supports using GHRP‑6 as a standalone GH‑releasing agent in acute protocols, such as pre‑workout or sleep‑time dosing, without needing to pair it with GHRH. However, the data come from a very small, short‑term study, so dosing should start low and be monitored for individual response.
Summary
The study shows that the synthetic peptide GHRP‑6 can trigger a rapid rise in growth hormone (GH) in humans even when the body's natural GH‑releasing hormone (GHRH) pathway is turned off. In a small test with five healthy men, giving GHRP‑6 after a 6‑hour GHRH infusion still produced a strong GH spike, proving that GHRP‑6 works through a different mechanism.
Abstract
The synthetic GH-releasing hexapeptide (GHRP: His-DTrp-Ala-Trp-DPhe-Lys-NH2) releases GH in man by an undetermined mechanism. To investigate whether acute GH response to GHRP is mediated by endogenous GHRH, we examined the effect of GHRP on GH release during pituitary desensitization to GHRH induced by short-term GHRH infusion. In five healthy men on six occasions, we infused saline (sal) or 1 microgram/kg.h GHRH-44 for 6 h. After 4 h, a bolus of sal, GHRH-44 1 microgram/kg body weight, or GHRP 1 microgram/kg body weight was given iv. GH concentration, measured by RIA, was analyzed by mean area under the curve (AUC) of GH released over the 2 h immediately after bolus injection. Infusion of GHRH had a biphasic effect on GH release; plasma GH increased to 12.7 +/- 3.3 micrograms/L within the first hour, with subsequent decrease to 2.9 +/- 0.3 micrograms/L during the last 2 h of infusion. GH AUC (hours 4-6 of infusion) microgram/L.2 h [table: see text] GH response to bolus GHRH was abolished by GHRH infusion, whereas GH response to GHRP persisted under the same conditions. Thus, we conclude that acute GH response to GHRP in humans is not mediated by endogenous GHRH.
Study Information
pubmed
1992
10.1210/jcem.75.4.1400881