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preclinicalGrowth & Recovery

GHRP-1

Also known as: Growth Hormone Releasing Peptide-1, GPA-748, GHRP-1 Acetate, His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂

GHRP-1 (GPA-748) is the first synthetic growth hormone releasing peptide discovered, a hexapeptide that acts on the growth hormone secretagogue receptor (GHS-R1a) to stimulate growth hormone release from the anterior pituitary. Developed in the early 1990s by Cyril Bowers, it laid the groundwork for all subsequent GHRPs (GHRP-2, GHRP-6, hexarelin) and ultimately led to the discovery of ghrelin, the endogenous GHS-R ligand. GHRP-1 remains a preclinical research tool and is not approved for human therapeutic use.

3 cited references·4 researched benefits

Quick Answer

GHRP-1 is the original synthetic growth hormone releasing peptide, a hexapeptide discovered by Cyril Bowers that stimulates GH release through the ghrelin/GHS-R1a receptor. It was the first compound to demonstrate that small synthetic peptides could trigger potent growth hormone secretion independent of GHRH, leading to the development of GHRP-2, GHRP-6, hexarelin, and ultimately the discovery of ghrelin. GHRP-1 remains a preclinical research compound.

Key Facts

Mechanism
GHRP-1 binds to the growth hormone secretagogue receptor type 1a (GHS-R1a) on pituitary somatotrophs, triggering intracellular calcium mobilization and growth hormone exocytosis. Like other GHRPs, it also acts at the hypothalamic level by suppressing somatostatin release and potentiating GHRH signaling. GHRP-1 was the proof-of-concept molecule demonstrating that synthetic peptides could activate the GH secretory pathway through a receptor distinct from the GHRH receptor — a finding that ultimately led to the identification of ghrelin as the endogenous GHS-R ligand in 1999.
Research Status
preclinical
Half-Life
~30 minutes
Molecular Formula
C₄₆H₅₆N₁₀O₆
Primary Use
Growth & Recovery
Table of Contents

Benefits

  • Potent stimulation of growth hormone release from the anterior pituitarystrong
  • Synergistic GH amplification when combined with GHRH (greater than additive effect)strong
  • Potential for improved body composition through GH/IGF-1 axis activationmoderate
  • Possible cytoprotective effects on gastric and cardiac tissue (shared GHRP class effect)preliminary

Dosage Protocols

RouteDosage RangeFrequencyNotes
Subcutaneous injection100–300 mcg2–3× daily on an empty stomachExtrapolated from GHRP-2/GHRP-6 protocols. GHRP-1 has limited human dosing data as it was primarily a research tool superseded by GHRP-2 and GHRP-6.
Intravenous (research setting)1 mcg/kgSingle bolusUsed in early GH provocation studies to characterize GHS-R activation. Not a clinical dosing protocol.

Medical disclaimer

Dosage information is provided for educational reference only. Always follow your prescriber's instructions and consult a qualified healthcare provider before starting any peptide protocol.

Side Effects

  • Increased appetite due to ghrelin receptor activationcommon
  • Elevated cortisol and prolactin levels (less selective than ipamorelin)common
  • Water retention and mild bloatingcommon
  • Potential insulin resistance with prolonged supraphysiologic GH elevationserious
Comparisons

Frequently Asked Questions

Why is GHRP-1 less commonly used than GHRP-2 or GHRP-6?
GHRP-1 was the first growth hormone releasing peptide discovered, but it was quickly superseded by optimized analogs. GHRP-2 provides a stronger and more consistent GH response with better pharmacological properties, while GHRP-6 became widely available and well-characterized. GHRP-1 remained primarily a research tool used in academic studies to understand GHS-R biology, and it was never developed for clinical application. Most peptide suppliers focus on GHRP-2 and GHRP-6 because of their more extensive human data.
How did GHRP-1 lead to the discovery of ghrelin?
GHRP-1 and its analogs demonstrated that a specific receptor existed on pituitary cells that was distinct from the GHRH receptor. This "orphan receptor" (GHS-R1a) was cloned in 1996. Researchers then searched for its endogenous ligand — the natural molecule the body makes to activate this receptor. In 1999, Kojima and colleagues discovered ghrelin, a 28-amino-acid peptide produced primarily by the stomach, as the endogenous GHS-R ligand. Without the synthetic GHRPs pioneered by GHRP-1, ghrelin might not have been discovered for years.
Does GHRP-1 cause hunger like GHRP-6?
Yes, GHRP-1 activates the GHS-R1a (ghrelin receptor), which is the same receptor that mediates hunger signaling. Like GHRP-6, it stimulates appetite, though the degree may differ somewhat between the peptides. Users seeking GH release without significant appetite stimulation generally prefer ipamorelin, which is uniquely selective for GH release and does not significantly affect hunger, cortisol, or prolactin.

References

  1. 1
    A new and potent growth hormone-releasing peptide: GHRP-1 (GPA-748) stimulates GH release in vitro and in vivo(1993)PubMed ↗
  2. 2
    Growth hormone releasing peptides: chemistry and biology of the GHS-R and its ligands(1997)PubMed ↗
  3. 3
    Growth hormone secretagogue receptor family members and ligands: recent advances and new questions(2005)PubMed ↗

Latest Research

Last updated: 2026-02-19