GH-Releasing Peptides (GHRP Family): A Complete Overview

These materials are research-grade reference compounds sold for laboratory research use only. They are not for human or veterinary use.

The growth-hormone-releasing peptides (GHRPs) are a family of short synthetic peptides studied at the ghrelin receptor. They form one half of the broader growth-hormone secretagogue category, the other being the GHRH analogs. The GHRP story is also a landmark in endocrinology, because the study of these synthetic peptides is what ultimately led researchers to the ghrelin receptor and its natural ligand. This overview maps the family, explains its history, and links to each compound’s reference page and comparison article.

At a Glance

• GHRPs are short synthetic peptides studied at the ghrelin receptor (GHS-R1a).
• The family includes GHRP-2, GHRP-6, hexarelin, and ipamorelin.
• The GHRP series contributed to the discovery of ghrelin and its receptor.
• Family members differ mainly in sequence and selectivity.
• All are research chemicals for laboratory use only.

What Defines the GHRP Family

GHRPs are short peptides, typically penta- or hexapeptides containing non-natural residues, that act as agonists at the growth-hormone-secretagogue receptor, GHS-R1a. Their cationic and aromatic residues and their use of D-amino acids are characteristic design features associated with receptor interaction and resistance to degradation. What unites the family is this shared receptor and the common secretagogue pharmacology.

A Landmark in Endocrinology

The GHRPs came before their target was understood. Researchers characterized the secretagogue activity of these synthetic peptides first, and that work pointed to the existence of a dedicated receptor, which was later identified along with its natural ligand, ghrelin (Bowers, 2012; Kojima et al., 1999). The family therefore has a historical significance beyond its individual members.

Members Mapped

Compound	Note	Reference
GHRP-6	Early GHRP; His-D-Trp-Ala-Trp-D-Phe-Lys-NH2	Reference page
GHRP-2 (pralmorelin)	Later GHRP; D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2	See reference page
Hexarelin	Earlier, broader-profile GHRP	Reference page
Ipamorelin	Selective GHRP (pentapeptide)	Reference page

Shared Themes in the Literature

The family is studied for ghrelin-receptor pharmacology and secretagogue activity in animal and cell models (Bowers, 2012). Within the family, the members are compared on sequence and selectivity, with ipamorelin noted for a narrow, selective profile in its founding report (Raun et al., 1998) and the earlier members associated with broader activity. Endogenous ghrelin provides the natural-ligand reference point for interpreting these studies (Kojima et al., 1999).

How the Family Is Studied

Research focuses on receptor binding and signaling, selectivity within the growth-hormone axis, and sequence-activity relationships, using animal and cell-based systems. Comparisons between family members, such as GHRP-6 versus GHRP-2 and ipamorelin versus hexarelin, are a common way to study how sequence changes affect the secretagogue profile.

Chemical Identity and Verification

Each GHRP is verified by HPLC for purity and mass spectrometry for identity, documented on the per-lot Certificate of Analysis. The presence of non-natural residues makes accurate identity confirmation important, and per-lot documentation is the reference.

Handling and Documentation

Store sealed material cold, shield it from light, and avoid repeated freeze-thaw. Lot-specific stability is documented on the COA; current lot reports are on the Lab Reports page.

Research Limitations and Open Questions

The GHRP literature rests largely on animal and cell models, so findings do not translate directly to any human context. Because the members are closely related, some secondary sources describe them interchangeably; researchers should rely on the specific sequence and the primary literature for the model of interest.

Frequently Asked Questions

What are growth-hormone-releasing peptides?

Short synthetic peptides that act as agonists at the ghrelin receptor, studied as growth-hormone secretagogues.

How do they relate to ghrelin?

The GHRP series preceded and helped lead to the discovery of the ghrelin receptor and its natural ligand.

How do family members differ?

Mainly in sequence and selectivity within the growth-hormone axis.

Which GHRP is the most selective?

Ipamorelin was characterized as the first selective GHRP in its founding report (Raun et al., 1998).

Is GHRP-2 the same as pralmorelin?

Yes, GHRP-2 is also known as pralmorelin.

How are they verified?

By HPLC and mass spectrometry, documented on the per-lot 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

• Growth-Hormone Secretagogue Research Peptides (parent overview)
• GHRP-6 vs GHRP-2; Ipamorelin vs Hexarelin (comparisons)
• Lab Reports

References

1. Bowers CY. History to the discovery of ghrelin. Methods Enzymol. 2012. PMID 22975043.
2. Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998. PMID 9849822.
3. Kojima M, et al. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 1999. PMID 10604470.

Research-use notice: GHRP-family peptides 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.