What receptor does ipamorelin act on?

GHS-R1a, the ghrelin receptor, which is a different receptor from CJC-1295's GHRH receptor.

What does selective mean here?

GH release without the cortisol and prolactin increases seen with earlier secretagogues. It is a claim about absent effects.

Ipamorelin and the Ghrelin Receptor

The short answer

Ipamorelin is an agonist at the growth hormone secretagogue receptor GHS-R1a, whose endogenous ligand is ghrelin. Its reported distinction is selectivity: GH release without the cortisol and prolactin increases that accompanied earlier compounds in the class.

Key facts

Receptor: GHS-R1a (ghrelin receptor)
Endogenous ligand: Ghrelin
Receptor class: G-protein-coupled
Reported selectivity: GH without cortisol or prolactin
Contrast: CJC-1295 acts at the GHRH receptor
Key reference: Raun 1998 (PMID 9849822)

What ghrelin is

Ghrelin is a stomach-derived peptide hormone, best known for stimulating appetite, that also acts at the pituitary to promote growth hormone release. Its receptor, GHS-R1a, was identified as a growth hormone secretagogue receptor before ghrelin itself was found, which is why the receptor's name refers to secretagogues rather than to its natural ligand.

The selectivity claim

Earlier secretagogues activated the same receptor but also produced increases in cortisol and prolactin. Those are not trivial confounds; cortisol in particular affects almost every system being measured. Raun and colleagues reported ipamorelin releasing GH without them, which is what the word selective in their title refers to. It is a claim about what the compound does not do.

Research material referenced

CJC-1295 + Ipamorelin 5+5mg, third-party HPLC tested

Buy CJC-1295 + Ipamorelin · £36.99

Why selectivity is achievable at all

A receptor can couple to more than one downstream pathway, and different ligands can favour different ones. This is the biased agonism principle described elsewhere in this library for GLP-1. Whether ipamorelin's selectivity arises from signalling bias, from receptor-subtype preference, or from pharmacokinetics is not something the 1998 paper settles, but the phenomenon is well precedented.

A different pathway from CJC-1295

This is the entire basis for studying them together. CJC-1295 acts at the GHRH receptor; ipamorelin at the ghrelin receptor. Two distinct receptors, two distinct signalling routes, converging on the same pituitary output. That is real mechanistic non-overlap rather than an asserted one.

What is not established

Ipamorelin holds no marketing authorisation anywhere, and there is no established clinical programme comparable to BPC-157's. The receptor pharmacology is well characterised; what administration achieves in people is not, and this library makes no claim about it.

Frequently asked questions

What receptor does ipamorelin act on?: GHS-R1a, the ghrelin receptor, which is a different receptor from CJC-1295's GHRH receptor.
What does selective mean here?: GH release without the cortisol and prolactin increases seen with earlier secretagogues. It is a claim about absent effects.
Why is the receptor named after secretagogues rather than ghrelin?: It was identified as a growth hormone secretagogue receptor before ghrelin, its endogenous ligand, was discovered.

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.

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.

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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.

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How Ipamorelin Acts at the Ghrelin Receptor