The short answer
GHRP-2, GHRP-6 and ipamorelin all act at the ghrelin receptor GHS-R1a. The distinction reported for ipamorelin is selectivity: GH release without the cortisol and prolactin increases the earlier GHRPs produced.
Key facts
- Shared receptor
- GHS-R1a
- GHRP-6
- Earlier compound; appetite effects reported
- GHRP-2
- Later; cortisol and prolactin effects reported
- Ipamorelin
- Reported selective for GH
- Basis of claim
- Raun 1998 (PMID 9849822)
- All
- No marketing authorisation; WADA-prohibited
One receptor, several ligands
The growth hormone secretagogue receptor GHS-R1a is the common target. GHRP-6 came first, GHRP-2 followed, and ipamorelin was developed later with selectivity as an explicit design objective. They are a sequence of attempts at the same target rather than unrelated compounds.
What the earlier compounds also did
GHRP-6 is associated with reported appetite stimulation, which is consistent with acting at the ghrelin receptor given ghrelin's role in hunger. GHRP-2 is associated with reported increases in cortisol and prolactin. Neither is a defect exactly; they are consequences of engaging a receptor whose natural ligand does more than one thing.
Research material referenced
CJC-1295 + Ipamorelin 5+5mg, third-party HPLC tested
Why selectivity was worth pursuing
Cortisol in particular is a serious confound. It affects metabolism, immune function, protein turnover and mood, so a compound raising it alongside GH makes any observed effect hard to attribute. A GH secretagogue that does not move cortisol is a cleaner research tool regardless of any therapeutic consideration.
How selectivity might arise
The 1998 paper reports the observation rather than explaining it. Plausible mechanisms include biased signalling at the receptor, differing pharmacokinetics producing different exposure profiles, or differences in where the compounds distribute. The biased agonism concept described for GLP-1 elsewhere in this library is the same idea applied to a different receptor.
What none of them has
A marketing authorisation. All are prohibited in sport under the WADA list. The comparison here is between research compounds on their reported pharmacology, not between treatments.
Quick reference
| GHRP-6 | GHRP-2 | Ipamorelin | |
|---|---|---|---|
| Receptor | GHS-R1a | GHS-R1a | GHS-R1a |
| Reported appetite effect | Yes | Less | Not reported |
| Reported cortisol effect | Reported | Reported | Not reported |
| Reported prolactin effect | Reported | Reported | Not reported |
| Selectivity claim | No | No | Yes (Raun 1998) |
Frequently asked questions
- Do they act on different receptors?
- No. All three act at GHS-R1a. The difference is in what else they were reported to do.
- Why does cortisol matter?
- It affects metabolism, immunity, protein turnover and mood, making any observed effect hard to attribute to GH alone.
- Is ipamorelin's selectivity explained?
- The 1998 paper reports it rather than explaining it. Biased signalling and pharmacokinetic differences are plausible mechanisms.
Extended research context
The CJC-1295 & Ipamorelin deep dive
Deep dive: why CJC-1295 and Ipamorelin are studied together
CJC-1295 is a modified GHRH (growth-hormone-releasing hormone) analogue; Ipamorelin is a selective growth-hormone secretagogue that binds the ghrelin receptor (GHS-R1a). In pituitary-cell research models the two act on independent pathways whose downstream effect converges on GH release. CJC-1295 amplifies the endogenous GHRH signal while Ipamorelin adds a separate ghrelin-pathway stimulus. That's why supplier catalogues frequently package them together as a research reference blend.
DAC vs no-DAC: which CJC-1295 is which
'CJC-1295 with DAC' contains a Drug Affinity Complex (a Lys-maleimide moiety) that binds serum albumin and extends half-life to several days. 'CJC-1295 no-DAC' (also called Modified GRF 1-29) lacks the linker and clears in minutes. These are pharmacologically different peptides. A CoA must specify which form is in the vial; mass differs (~3,367 Da with DAC vs ~3,367 minus linker for no-DAC).
Ipamorelin's selectivity profile
Unlike earlier GHS-R agonists (e.g. GHRP-6), Ipamorelin was engineered for minimal cross-activity at cortisol- and prolactin-releasing pathways in research models. That receptor selectivity is why it is the reference secretagogue for controlled pituitary-cell studies.
Research applications
- ▸Pituitary-cell GH-release assays (comparator vs GHRH and hexarelin)
- ▸Half-life comparison studies: DAC vs no-DAC CJC-1295 forms
- ▸Ghrelin-receptor binding assays for Ipamorelin analogue development
- ▸Analytical HPLC method development for lipidated GHRH analogues
- ▸Stability testing under refrigerated storage
Handling checklist
- ✓Store lyophilised at −20 °C long-term
- ✓Reconstitute in bacteriostatic water; both peptides dissolve readily
- ✓Aliquot immediately, refrigerate at 2–8 °C, use within 28 days
- ✓Confirm salt form and DAC/no-DAC status on CoA before starting a study
- ✓Do not use for human administration (research reference only)
Common research-handling mistakes
Learnt from thousands of researcher orders across our UK labs.
✗ Confusing DAC and no-DAC CJC-1295
Fix: Check the CoA. The two have very different pharmacokinetics.
✗ Assuming Ipamorelin acts on GHRH receptors
Fix: It binds the ghrelin receptor (GHS-R1a), a separate pathway from CJC-1295.
✗ Storing reconstituted solution at room temperature
Fix: Refrigerate 2–8 °C after reconstitution.
Continue researching
Peer-reviewed guides, comparators and matched reference materials.
Related questions researchers ask
- Is CJC-1295 the same as Modified GRF 1-29?
- What is the difference between DAC and no-DAC CJC-1295?
- Does Ipamorelin raise cortisol?
- Why are CJC-1295 and Ipamorelin blended together?
- How long is the half-life of CJC-1295 with DAC?
Primary sources & clinical trials
Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.
- PubMedRaun K et al., Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol 1998 (PMID 9849822)pubmed.ncbi.nlm.nih.gov
- PubMedMüller TD et al., Ghrelin. Molecular Metabolism 2015 (PMID 26042199)pubmed.ncbi.nlm.nih.gov
- RefWADA Prohibited Listwada-ama.org
- PubMedTeichman et al., Prolonged stimulation of GH & IGF-I by CJC-1295. J Clin Endocrinol Metab 2006 (PMID 16352683)pubmed.ncbi.nlm.nih.gov
- PubChemPubChem · CJC-1295 / mod GRF (1-29) (CID 56841945)pubchem.ncbi.nlm.nih.gov
- PubChemPubChem · CJC-1295 with DAC (CID 91971820)pubchem.ncbi.nlm.nih.gov
- PubChemPubChem · Ipamorelin (CID 9831659)pubchem.ncbi.nlm.nih.gov
- TrialClinicalTrials.gov · GH-secretagogue trialsclinicaltrials.gov
- GuidelineGoogle: Creating helpful, reliable, people-first contentdevelopers.google.com
Written and reviewed by
The UK Peptides Editorial Team · Research library, UK Peptides
The editorial team is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate. Corrections are made in place and the review date updated.
More CJC-1295 & Ipamorelin articles
- Why These Two Are Studied TogetherTwo receptors, one output. The mechanistic rationale for pairing a GHRH analogue with a ghrelin receptor agonist — and what would be needed to test it.
- Synergy: A Word Worth Using CarefullyAdditive and synergistic are different claims with different evidential requirements. What would have to be shown, and what has been.
- The Teichman 2006 CJC-1295 StudyThe landmark pharmacokinetic study of CJC-1295 with DAC in healthy adults, published in JCEM in 2006 — and why it is sometimes miscited as Walker.
- What the Published Literature ContainsTwo human pharmacokinetic studies from 2006, a 1998 selectivity paper, and comparatively little else. A small but unusually clinical evidence base.
- Storage and Reconstitution for Both CompoundsTwo peptides differing fivefold in mass, stored together but not identical. Why the DAC form's maleimide is the one genuinely reactive feature here.
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