# GHRP-6

> The original growth-hormone-releasing peptide — the tool compound that led scientists to the ghrelin receptor and, ultimately, to ghrelin itself.

- Also known as: Growth Hormone Releasing Peptide-6, Growth hormone-releasing hexapeptide, GHRP
- Class: Growth Hormone
- FDA approved: No
- Canonical page: https://americanpeptide.com/catalog/ghrp-6

## Overview

GHRP-6 is the first-generation growth-hormone-releasing peptide and the historical starting point of the entire GHRP field. A synthetic hexapeptide that activates the GHS-R1a (ghrelin) receptor, it is pivotal beyond its own effects: the hunt for the receptor GHRP-6 bound led to the 1996 cloning of the GH-secretagogue receptor and, in 1999, to the discovery of its natural ligand, ghrelin.

GHRP-6 is where the story of this whole class begins. Grown out of Cyril Bowers’ work on enkephalin-derived peptides, it was among the first peptides shown to release growth hormone through a receptor entirely separate from GHRH. That receptor was an orphan — no one knew its natural ligand — and GHRP-6 became the pharmacological probe used to find it.

The payoff was foundational: in 1996 the GH-secretagogue receptor (GHS-R1a) was cloned, and in 1999 its endogenous ligand, the stomach hormone ghrelin, was identified — reframing GHRP-6 in hindsight as a synthetic mimic of a hormone that had not yet been discovered. Pharmacologically, GHRP-6’s other signature is appetite: it is the GHRP most associated with a sharp, ghrelin-like spike in hunger, which itself became a research tool for probing feeding circuits. It is not FDA-approved.

## Mechanism

GHS-R1a (ghrelin receptor) agonism → GH release and appetite stimulation.

## Chemistry

| Property | Value |
| --- | --- |
| Molecular formula | C46H56N12O6 |
| Molecular weight | 873.04 Da |
| CAS number | 87616-84-0 |
| PubChem CID | [4345065](https://pubchem.ncbi.nlm.nih.gov/compound/4345065) |

## Sequence

```
His-D-Trp-Ala-Trp-D-Phe-Lys-NH2
```

## Research areas

Studied in: GH secretion studies, Ghrelin-receptor biology, Appetite regulation.

Guides on this site:

- [Growth Hormone & Body Composition](https://americanpeptide.com/research-areas/growth-hormone-axis): Secretagogues studied for GH release, IGF-1, and body composition.

## Key research

- Discovery tool — the probe compound whose target hunt led to cloning the GH-secretagogue receptor (GHS-R1a, 1996) and identifying ghrelin (1999).
- GH release via a non-GHRH pathway — helped establish that a peptide could release GH through a receptor separate from the GHRH receptor.
- Appetite stimulation — the GHRP most strongly associated with acute, ghrelin-like hunger; used to study feeding and energy-balance circuits.
- Compared to GHRP-2 / ipamorelin — the original and least selective of the family; newer GHRPs were engineered from it for more GH per dose (GHRP-2) or fewer off-target effects (ipamorelin).
- Not FDA-approved — a research compound; often studied with a GHRH analog for complementary release.

## Storage, handling & synthesis

**Synthesis.** A hexapeptide amide built from standard Fmoc building blocks, including D-Trp and D-Phe. A short, straightforward solid-phase assembly; the main concerns are C-terminal amidation and protecting the oxidation- and light-sensitive tryptophan residues during synthesis and storage.

## FAQs

### What is GHRP-6?

GHRP-6 is the first growth-hormone-releasing peptide — a synthetic hexapeptide that releases GH by activating the ghrelin receptor, and the compound whose study led to the discovery of that receptor and of ghrelin itself.

### Why is GHRP-6 historically important?

It was the pharmacological probe used to identify the GH-secretagogue receptor (cloned 1996) and its natural hormone, ghrelin (1999) — making it foundational to a whole area of endocrinology.

### Why does GHRP-6 cause hunger?

It activates the ghrelin receptor, and ghrelin is the body’s hunger signal; GHRP-6 is the GHRP most associated with a sharp increase in appetite.

### How does it compare with GHRP-2 and ipamorelin?

GHRP-6 is the original and least selective; GHRP-2 was tuned for more potency and less hunger, and ipamorelin for GH release with minimal cortisol or prolactin.

### Is GHRP-6 approved?

No — it is a research compound. This page is a research and educational reference.

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Source: AmericanPeptide.com — https://americanpeptide.com/catalog/ghrp-6
Data license: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Attribution: AmericanPeptide.com.
Research reference only — computational and educational content, not medical advice.