GHRP-2 vs GHRP-6 vs hexarelin vs ipamorelin.
GHRP-2, GHRP-6, hexarelin and ipamorelin are short synthetic peptides that release growth hormone through the ghrelin receptor. They share a family history and a receptor but differ in structure and in what else they did in research models. Here they are side by side.
Four secretagogues in one table.
| GHRP-6 | GHRP-2 | Hexarelin | Ipamorelin | |
|---|---|---|---|---|
| Sequence | His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 | D-Ala-D-2Nal-Ala-Trp-D-Phe-Lys-NH2 | His-D-2-Me-Trp-Ala-Trp-D-Phe-Lys-NH2 | Aib-His-D-2Nal-D-Phe-Lys-NH2 |
| Length | 6 residues | 6 residues | 6 residues | 5 residues |
| Formula | C46H56N12O6 | C45H55N9O6 | C47H58N12O6 | C38H49N9O5 |
| Molecular weight | 873.0 g/mol | 818.0 g/mol | 887.0 g/mol | 711.9 g/mol |
| PubChem CID | 9919153 | 6918245 | 6918297 | 9831659 |
| Other names | SKF-110679 | Pralmorelin, KP-102 | Examorelin | NNC 26-0161 |
| First reported | 1984, Bowers and colleagues | Developed for diagnostic use by Kaken, Japan | 1994, Deghenghi and a Milan group | 1998, Raun and colleagues |
Formulas and masses from PubChem. D-Trp, D-Phe and D-Ala are mirror-image forms of the usual amino acids; 2Nal is 2-naphthylalanine, 2-Me-Trp is 2-methyltryptophan and Aib is aminoisobutyric acid. All four end in a C-terminal amide.
Drugs before the hormone.
Cyril Bowers' group at Tulane began making synthetic growth hormone releasing peptides in 1976, and GHRP-6 was reported in 1984 as a hexapeptide that released growth hormone without releasing LH, FSH, TSH or prolactin, in species from rats to calves. Their receptor was cloned from pituitary and hypothalamus in 1996 and is now named the ghrelin receptor, GHS-R1a. Ghrelin, the hormone that naturally activates it, was found only afterwards, which is why these peptides are called ghrelin mimetics.
Same receptor, different side effects in models.
Ipamorelin is described as the first selective growth hormone secretagogue. In a 1998 study it matched GHRP-6 for growth hormone release in rat pituitary cells, rats and swine; in swine, GHRP-6 and GHRP-2 also raised ACTH and cortisol, while ipamorelin stayed at levels like those of GHRH across the range tested. None of the peptides changed FSH, LH, prolactin or TSH.
GHRP-6 made animals eat: more food intake was the first effect beyond growth hormone that Bowers' group noticed, and given into the brain ventricles of sated rats it triggered eating without changing growth hormone.
Hexarelin swaps GHRP-6's D-tryptophan for the more stable 2-methyl-D-tryptophan, with growth hormone release in rats similar to GHRP-6. It also binds a site in the heart, identified in 2002 as the scavenger receptor CD36.
GHRP-2, or pralmorelin, was developed in Japan as a diagnostic agent: a GHRP-2 test was validated for adult growth hormone deficiency, and by 2016 it was the only ghrelin receptor ligand to have reached the market, for that diagnostic use in Japan.
Identity by mass.
The four differ in mass, so mass spectrometry tells them apart, and HPLC measures purity. Mirror-image residues do not change the mass, so the lab's method and reference standard matter for confirming the right isomer. How peptides are tested explains each result on a report.
Ipamorelin in the CJC-1295 blend.
Helion supplies ipamorelin in its CJC-1295 (no DAC) + Ipamorelin 10mg blend (CP10), whose lot 335XA tested at 99.85% HPLC purity at ILS Laboratories, for laboratory research use only. It does not supply GHRP-2, GHRP-6 or hexarelin. CJC-1295 vs ipamorelin explains how the two in the blend differ, and tesamorelin vs sermorelin vs ipamorelin compares ipamorelin with the GHRH analogs.
Specs and storage by compound.
Questions (7)
What is the difference between GHRP-2 and GHRP-6?
Both are hexapeptides that act on the ghrelin receptor. GHRP-2 (pralmorelin) uses D-alanine and 2-naphthylalanine and was developed as a diagnostic agent in Japan; GHRP-6 was the first of the series, reported in 1984, and increased food intake in rats.
Is ipamorelin a GHRP?
It belongs to the same family of ghrelin receptor agonists. It is a pentapeptide, and a 1998 study described it as the first selective growth hormone secretagogue.
What is hexarelin?
A hexapeptide like GHRP-6 with 2-methyl-D-tryptophan in place of D-tryptophan. It also binds CD36 in the heart.
What is pralmorelin?
The international name for GHRP-2, developed by Kaken in Japan as a diagnostic agent for growth hormone deficiency.
What receptor do GHRPs act on?
The growth hormone secretagogue receptor, GHS-R1a, now named the ghrelin receptor.
Which GHRP is the most selective?
Ipamorelin. In swine, GHRP-6 and GHRP-2 also raised ACTH and cortisol, while ipamorelin stayed at GHRH-like levels.
Does Helion sell GHRP-2 or GHRP-6?
No. Helion supplies ipamorelin in its CJC-1295 (no DAC) + Ipamorelin 10mg blend, for laboratory research use only.
Published studies (10)
- On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone
- History to the discovery of ghrelin
- Ipamorelin, the first selective growth hormone secretagogue
- A receptor in pituitary and hypothalamus that functions in growth hormone release
- International Union of Pharmacology. LVI. Ghrelin receptor nomenclature, distribution, and function
- Intracerebroventricular growth-hormone-releasing peptide-6 stimulates eating without affecting plasma growth hormone responses in rats
- GH-releasing activity of Hexarelin, a new growth hormone releasing peptide, in infant and adult rats
- CD36 mediates the cardiovascular action of growth hormone-releasing peptides in the heart
- A simple diagnostic test using GH-releasing peptide-2 in adult GH deficiency
- Ghrelin Receptor Ligands Reaching Clinical Trials: From Peptides to Peptidomimetics; from Agonists to Antagonists
Citations from PubMed for reference. They describe the compound in the literature, not any Helion lot, and nothing here is guidance on use.