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GHRP-6 vs GHRP-2: A Complete Research Comparison
These materials are research-grade reference compounds sold for laboratory research use only. They are not for human or veterinary use.
GHRP-6 and GHRP-2 are two of the earliest and most studied members of the growth-hormone-releasing peptide family. They are close relatives: both are synthetic hexapeptides that act at the ghrelin receptor, and both belong to the historical GHRP series that helped lead researchers to the discovery of ghrelin itself. The comparison between them is therefore a within-family comparison, focused on sequence-level differences rather than differences in class.
This article compares them in depth and strictly in research terms: their sequences, the shared receptor mechanism, what the literature reports in animal and cell models, and how each is verified and handled. Every finding is framed within its experimental context, and nothing here is guidance for human or veterinary use.
At a Glance
- Both are synthetic hexapeptides studied at the ghrelin receptor (GHS-R1a).
- GHRP-6 is commonly represented as His-D-Trp-Ala-Trp-D-Phe-Lys-NH2.
- GHRP-2 (also called pralmorelin) is commonly represented as D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2.
- They belong to the historical GHRP series central to ghrelin research.
- Both are research chemicals for laboratory use only, verified per lot by HPLC and mass spectrometry.
Quick Comparison
| Attribute | GHRP-6 | GHRP-2 |
|---|---|---|
| Class | Growth-hormone-releasing peptide | Growth-hormone-releasing peptide |
| Receptor studied | Ghrelin receptor (GHS-R1a) | Ghrelin receptor (GHS-R1a) |
| Representative sequence | His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 | D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2 |
| Also known as | GHRP-6 | Pralmorelin |
| Comparison axis | Sequence-level differences within the family | Sequence-level differences within the family |
| Verification | HPLC + mass spectrometry, per-lot COA | HPLC + mass spectrometry, per-lot COA |
What GHRP-6 Is?
GHRP-6 is a synthetic hexapeptide, commonly represented as His-D-Trp-Ala-Trp-D-Phe-Lys-NH2. It is one of the earliest growth-hormone-releasing peptides and features prominently in the historical work that characterized the secretagogue response and, ultimately, the ghrelin receptor (Bowers, 2012). Its two tryptophan residues and D-amino acids are characteristic design features of the early GHRP series. Exact molecular weight and purity for any lot are documented on the Certificate of Analysis.
What GHRP-2 Is?
GHRP-2, also known as pralmorelin, is a synthetic hexapeptide commonly represented as D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2. It is a later member of the GHRP series, studied at the same ghrelin receptor. Its sequence differs from GHRP-6 at several positions, most notably the N-terminal residues, which is the structural basis for their distinct research profiles. Exact molecular weight and purity for any lot are documented on the Certificate of Analysis.
A Shared Receptor and Family History
Both peptides act at the growth-hormone-secretagogue receptor, GHS-R1a. The GHRP series to which they belong preceded the identification of the receptor’s natural ligand, and that body of work established the pharmacology of the family and pointed the way to ghrelin (Bowers, 2012; Kojima et al., 1999). This shared history is why GHRP-6 and GHRP-2 are compared within a family rather than across classes.
What the Research Literature Reports?
The GHRP literature situates both peptides as ghrelin-receptor agonists studied as growth-hormone secretagogues in animal and cell models (Bowers, 2012). Within the family, the members are studied for how their sequence differences translate into differences in receptor interaction and secretagogue profile. Endogenous ghrelin provides the natural-ligand reference point for interpreting these studies (Kojima et al., 1999). All findings are reported within their specific research systems and are not statements about human use.
Structure, Stability, and Research Handling
Both are short synthetic hexapeptides containing D-amino acids, features associated with resistance to some enzymatic degradation and typical of the GHRP series. They are generally soluble in aqueous buffers, though exact behavior depends on the sequence and lot. General peptide-stability principles apply, and lot-specific stability is documented on the Certificate of Analysis rather than as a blanket duration.
How Researchers Choose Between Them
Because they are so closely related, the choice comes down to sequence-level differences, the specific research question, and the depth of prior literature for the model of interest. Researchers studying the historical characterization of the secretagogue response often reference GHRP-6, while GHRP-2 (pralmorelin) is studied as a later, distinct member of the same family.
Chemical Identity and Verification
Both are verified by mass spectrometry for identity and HPLC for purity, with results on a lot-specific Certificate of Analysis. Net peptide content is distinct from chromatographic purity. Reconcile every molecular figure, including sequence and mass, against the COA before use.
Storage and Handling in a Laboratory Context
Store sealed material cold, shield it from light, and avoid repeated freeze-thaw. Lyophilized material is generally more stable than material in solution. Lot-specific stability is documented on the COA.
Research Limitations and Open Questions
Both peptides are studied largely in animal and cell models, and findings do not translate directly to any human context. Because they are close relatives, some secondary sources describe them interchangeably; researchers should rely on the specific sequence and the primary literature for the model and endpoint of interest.
Frequently Asked Questions
What is the difference between GHRP-6 and GHRP-2?
They are closely related growth-hormone-releasing peptides that differ in sequence, especially at the N-terminus, and are studied within the same family at the ghrelin receptor.
What are their sequences?
GHRP-6 is commonly His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 and GHRP-2 is commonly D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2. Confirm the exact sequence for a given lot against its COA.
Is GHRP-2 the same as pralmorelin?
Yes, GHRP-2 is also known as pralmorelin.
How do they relate to ghrelin?
The GHRP series preceded and helped lead to the discovery of the ghrelin receptor and its natural ligand.
What research contexts is each studied in?
Both appear in growth-hormone secretagogue and ghrelin-receptor research in animal and cell models.
How is each verified for identity and purity?
By mass spectrometry for identity and HPLC for purity, documented on a lot-specific Certificate of Analysis.
Do these findings apply to people?
No. All cited work is in animal or cell models and describes mechanism and research outcomes only.
Related Reading
- GHRP-6 reference page
- GH-Releasing Peptides (GHRP family) overview
- Growth-Hormone Secretagogue Research Peptides (class overview)
- Lab Reports
References
- Bowers CY. History to the discovery of ghrelin. Methods Enzymol. 2012. PMID 22975043.
- Kojima M, et al. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 1999. PMID 10604470.
Research-use notice: GHRP-6 and GHRP-2 are research chemicals sold for laboratory research use only. They are not for human or veterinary use. Every finding is reported in the specific research context of the cited study.
