GHRPs, as a family.
GHRP-6, GHRP-2, hexarelin and ipamorelin are four short synthetic peptides that act at the same receptor, a receptor whose natural partner, ghrelin, was not found until fifteen years after the first of them was made. Read as a family they are easy to tell apart. Here is their shared history, the table that separates them and the two non-peptide molecules that belong in the same group.
Peptides before the receptor, receptor before the hormone.
In 1977 Cyril Bowers found that a synthetic fragment of met-enkephalin, stripped of its original activity, had a different one, and by 1984 his group had made GHRP-6, the first practical member of the family. The receptor those peptides bound was cloned at Merck in 1996 and named the growth hormone secretagogue receptor, GHS-R1a. Its natural ligand, ghrelin, was purified from rat stomach in 1999. So the family is unusual: the drugs came first, the receptor second and the hormone last.
Four peptides, two non-peptides.
| GHRP-6 | His-D-Trp-Ala-Trp-D-Phe-Lys-NH2; C46H56N12O6; 873.0 g/mol; CAS 87616-84-0; PubChem CID 4345065; 1984 |
|---|---|
| GHRP-2 (pralmorelin) | D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2; C45H55N9O6; 818.0 g/mol; CAS 158861-67-7; CID 6918245 |
| Hexarelin | His-D-2-Me-Trp-Ala-Trp-D-Phe-Lys-NH2; C47H58N12O6; 887.0 g/mol; CAS 140703-51-1; CID 6918297. Hexarelin |
| Ipamorelin | Aib-His-D-2-Nal-D-Phe-Lys-NH2; C38H49N9O5; 711.9 g/mol; CAS 170851-70-4; CID 9831659. Ipamorelin |
| MK-677 (ibutamoren) | Not a peptide: a spiroindoline; C27H36N4O5S; 528.7 g/mol; CAS 159634-47-6; CID 178024; 1995 |
| Anamorelin | Not a peptide; C31H42N6O3; 546.7 g/mol; CID 9828911; approved in Japan in 2021 |
Alternating D and L residues.
Every peptide in the family is five or six residues long, ends in Lys-NH2 and alternates L- and D-amino acids so that it survives proteases. The D-residues and the unusual ones, 2-naphthylalanine in GHRP-2 and ipamorelin, 2-methyl-D-tryptophan in hexarelin, aminoisobutyric acid at the start of ipamorelin, are what each catalog page has to spell out, because the one-letter codes cannot. How to read a peptide sequence covers the notation and GHRP-2 vs GHRP-6 vs hexarelin vs ipamorelin compares the four in detail.
Not GHRH analogues.
The GHRPs act at the ghrelin receptor. Sermorelin, CJC-1295 and tesamorelin act at the GHRH receptor and are a different family of larger peptides, 29 to 44 residues long; GHRH analogues as a family covers them. Research pairs one of each in a single vial, which is why blends such as CJC-1295 + ipamorelin exist and why the two names should never be treated as versions of one another.
MK-677 and anamorelin.
Two small molecules bind the same receptor and are grouped with the GHRPs as growth hormone secretagogues even though they contain no peptide bond. MK-677, ibutamoren, was reported by Merck in 1995 and has never been approved; anamorelin was approved in Japan in 2021. Both are listed separately from peptides in catalogs and tested by different methods, since the mass-spectrometry and HPLC conventions for peptides do not apply in the same way.
One approved, in one country.
None of the four peptides is an approved drug in the United States; GHRP-2 has been used as a diagnostic agent in Japan under the name pralmorelin, and anamorelin is approved there. All of the peptides are prohibited in sport by the World Anti-Doping Agency. Helion supplies research compounds under a research-use-only label; what research use only means explains it.
Ipamorelin, in a blend.
Helion supplies ipamorelin as half of the CJC-1295 (no DAC) + ipamorelin blend, 5 mg of each, with a per-lot third-party report in the COA Portal.
Specs and storage by compound.
Questions (6)
What is a GHRP?
A growth hormone releasing peptide: a short synthetic peptide, five or six residues with alternating D- and L-amino acids, that acts at the ghrelin receptor GHS-R1a.
Which peptides are GHRPs?
GHRP-6, GHRP-2 (pralmorelin), hexarelin and ipamorelin are the four common ones. MK-677 and anamorelin act at the same receptor but are not peptides.
Is ipamorelin a GHRP?
Yes. It is a pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH2, 711.9 g/mol, in the same family.
Are GHRPs the same as GHRH analogues?
No. GHRPs act at the ghrelin receptor; GHRH analogues such as sermorelin and CJC-1295 act at the GHRH receptor and are much longer peptides.
Is MK-677 a peptide?
No. MK-677 (ibutamoren) is a small molecule, a spiroindoline, that binds the same receptor as the GHRPs.
Which GHRP does Helion sell?
Ipamorelin, in a blend with CJC-1295 (no DAC), 5 mg of each per vial.
Published studies (2)
- A receptor in pituitary and hypothalamus that functions in growth hormone release
- Ghrelin is a growth-hormone-releasing acylated peptide from stomach
Citations from PubMed for reference. They describe the compound in the literature, not any Helion lot, and nothing here is guidance on use.