GHS-R Ligand Comparator

The GHS-R Ligand Comparator is a three-vial set containing GHRP-2, GHRP-6 and Ipamorelin at 10 mg each. All three are agonists at the growth hormone secretagogue receptor GHS-R1a, so the primary mechanism is held constant. What differs is the breadth of secondary endocrine response reported for each, forming a gradient from GHRP-6 through GHRP-2 to the more selective Ipamorelin.

Key Takeaways

• The GHS-R Ligand Comparator contains GHRP-2, GHRP-6 and Ipamorelin, all at 10 mg, supplied lyophilized.
• All three compounds are agonists at GHS-R1a, the growth hormone secretagogue receptor, and share a primary signalling route.
• The compounds differ in the breadth of secondary endocrine response reported at GH-releasing concentrations, forming a selectivity gradient.
• GHRP-6 and GHRP-2 are hexapeptides; Ipamorelin is a pentapeptide, and its improved selectivity came from a shorter redesigned sequence rather than added modifications.
• All three contain non-proteinogenic residues including D-amino acids, which affects both protease resistance and analytical verification.
• All three are supplied strictly for laboratory research and are not intended for human consumption, therapeutic use, veterinary use, or diagnostic applications.

What’s Included in This Research Set

All three vials are supplied as lyophilized powder with batch documentation.

One Receptor, Three Selectivity Profiles

The three compounds share a receptor and a primary action. They differ in what else they engage.

What all three compounds share

All three are agonists at GHS-R1a, the growth hormone secretagogue receptor, for which ghrelin is the endogenous ligand. GHS-R1a is a class A G protein-coupled receptor signalling through Gq/11 to phospholipase C, generating IP3 and diacylglycerol and raising intracellular calcium.

All three also act through a shared secondary route: reducing somatostatin restraint on the somatotroph. Growth hormone release under GHS-R1a agonism reflects both direct stimulation and this reduction in inhibitory tone.

Because the receptor and both routes are common to all three, differences between the compounds are not differences in primary mechanism.

GHRP-6 — the first-generation reference

GHRP-6 is a hexapeptide and the earliest of the three. Alongside GH-releasing activity, GHRP-6 is characterised in the literature by pronounced signalling through appetite-related pathways, reflecting GHS-R1a expression in hypothalamic regions beyond the somatotroph population.

That breadth makes GHRP-6 the reference point in this set. It is the compound against which “more selective” is defined, and a selectivity comparison without the broad-profile compound has nothing to measure from.

GHRP-2 — greater potency, broader secondary profile

GHRP-2, also known as pralmorelin and KP-102, is a second-generation hexapeptide. It is reported as more potent than GHRP-6 for GH release, with less pronounced appetite-axis signalling.

It carries its own documented secondary endpoints, however: prolactin, ACTH and cortisol responses appear in the published characterisation of GHRP-2 at concentrations producing GH release. Higher potency at the primary endpoint did not narrow the endocrine response.

Ipamorelin — selectivity by subtraction

Ipamorelin is a pentapeptide — five residues where both GHRPs have six. It was developed specifically to produce GH release with minimal prolactin, ACTH and cortisol response, and is described in the literature as the first selective growth hormone secretagogue.

The structural point is worth noting. Ipamorelin’s narrower profile came from a shorter, redesigned sequence rather than from additional modifications layered onto an existing one. Selectivity was achieved by subtraction.

Ipamorelin also incorporates α-aminoisobutyric acid, a non-proteinogenic residue, alongside D-amino acids shared with the other two compounds. See how GHRP-6 and ipamorelin compare.