GHRP · GHS-R1a agonist · Spoke 3.14

GHRP-2: the high-potency GH secretagogue — larger GH pulses than GHRP-6, but the cortisol trade-off remains.

Q: Is GHRP-2 stronger than GHRP-6?

GHRP-2 produces approximately 20–50% higher GH amplitude at equivalent doses versus GHRP-6 in most comparisons. Cortisol and prolactin co-stimulation are comparable or slightly lower.

Q: What is pralmorelin?

Pralmorelin is the INN for GHRP-2, registered in Japan as GHRP Kaken 100 as a diagnostic agent for testing pituitary GH reserve — the only pharmaceutical registration of GHRP-2.

By PeptideRadar Research Desk · April 30, 2026

SequenceD-Ala-D-β-Nal-Ala-Trp-D-Phe-Lys-NH₂ (6 aa) MW817.9 Da Half-life~30 min SC TargetGHS-R1a (ghrelin receptor) Updated2026-04-30

GHRP-2 (KP-102, also known as pralmorelin in its pharmaceutical form) is a second synthetic hexapeptide in the GHRP class, developed after GHRP-6 with structural modifications intended to improve metabolic stability and receptor binding. It produces the largest GH pulse of the early GHRP class at equivalent doses. Like GHRP-6, it co-stimulates cortisol and prolactin — the selectivity limitations that ipamorelin was subsequently engineered to address.

Key points

Hexapeptide GHS-R1a agonist; pharmaceutical designation "pralmorelin." More metabolically stable than GHRP-6 due to D-amino acid residues at positions 1 and 2.
Produces the largest acute GH pulse of the classical GHRP class — approximately 2x the GH amplitude of ipamorelin at equivalent doses in some studies.
Co-stimulates ACTH/cortisol and prolactin — equivalent or slightly less than GHRP-6; substantially more than ipamorelin.
Appetite stimulation is present but typically less pronounced than with GHRP-6.
Published human PK/PD data exists including from the pralmorelin (pharmaceutical name) development program.
Used in Japan as pralmorelin (GHRP Kaken 100) for GH deficiency diagnosis — one of the few GHRPs with any pharmaceutical registration outside Russia.

Structural modifications vs. GHRP-6

GHRP-2 incorporates D-amino acid residues at position 1 (D-Ala) and position 2 (D-β-Nal, a non-natural aromatic amino acid). Both modifications increase resistance to enzymatic degradation compared to GHRP-6's corresponding positions. The result is a longer effective half-life (~30 min vs ~15 min for GHRP-6 in rodent models) and improved receptor binding affinity at GHS-R1a.

Despite the structural differences, GHRP-2 and GHRP-6 share the same receptor target and produce qualitatively similar pharmacological profiles — the selectivity problem (cortisol/prolactin co-stimulation) is a property of the GHS-R1a receptor distribution, not a structural property that these modifications address. Ipamorelin's selectivity improvement required more fundamental design changes in the binding pharmacophore.

GH pulse pharmacology and pralmorelin data

GHRP-2 has published human PK/PD data including from its Japanese pharmaceutical development program as pralmorelin (GHRP Kaken 100):

Pralmorelin (GHRP-2) was approved in Japan for use as a diagnostic agent to test GH reserve — one of the few pharmacological registrations of a GHRP outside Russia. This required human clinical data demonstrating reliable GH stimulation.
Petersenn et al. published pharmacodynamic data showing that GHRP-2 produced GH pulses with peak concentrations approximately 2-fold higher than ipamorelin at equivalent weight-based doses in comparative studies (PMID: 10210532).
The GHRH synergy observed with GHRP-6 applies equally to GHRP-2 — combining GHRP-2 with a GHRH analog produces a supraadditive GH response (PMID: 8421098).
Dose-response studies show plateau behavior above approximately 1 mcg/kg SC — higher doses do not proportionally increase GH amplitude.

Cortisol and prolactin: the same trade-off as GHRP-6

GHRP-2 produces comparable or slightly attenuated cortisol and prolactin responses versus GHRP-6 — the difference is small in practice. Both are substantially higher than ipamorelin in these non-GH endpoints. The mechanism is the same: GHS-R1a agonism at hypothalamic and pituitary sites drives ACTH and prolactin release via mechanisms independent of the somatotroph GH release pathway.

For research contexts where GH amplitude is the primary endpoint and cortisol/prolactin co-stimulation are acceptable (or desirable for diagnostic purposes), GHRP-2 is the highest-potency option in the classical GHRP class. For contexts where cortisol/prolactin co-stimulation is undesirable, ipamorelin remains the preferred compound.

GHRP-2 as a diagnostic tool (pralmorelin)

The pralmorelin (GHRP-2) diagnostic use in Japan is worth noting because it represents one of the more rigorous pharmacological characterizations of any research GHRP. The compound's reliability in stimulating a measurable GH response — and the characterization of that response across different populations — provides more pharmacological data than most research peptides. The diagnostic literature should be read with the caveat that it describes the expected pharmacological effect in clinical populations, not a therapeutic benefit.

Comparison table: GHRP-2 vs. GHRP-6 vs. ipamorelin

Parameter	GHRP-2	GHRP-6	Ipamorelin
GH pulse amplitude	Largest	Large	Moderate-Large
Cortisol elevation	Moderate-High	High	Minimal
Prolactin elevation	Moderate	Moderate-High	Minimal
Appetite stimulation	Moderate	Strong	Minimal
Half-life (SC)	~30 min	~15–30 min	~2 hr
Pharmaceutical registration	Japan (diagnostic)	None	Phase II (discontinued)

Frequently asked

Is GHRP-2 stronger than GHRP-6?

GHRP-2 produces a larger GH pulse at equivalent doses in most head-to-head comparisons — approximately 20–50% higher GH amplitude depending on the study. This comes with comparable or slightly reduced cortisol and prolactin co-stimulation. The "stronger" label is accurate for GH output but should not imply improved safety or anabolic profile.

What is pralmorelin?

Pralmorelin is the INN (international nonproprietary name) for GHRP-2. It is registered in Japan under the name GHRP Kaken 100 as a diagnostic agent for testing pituitary GH reserve. This is the only pharmaceutical registration of GHRP-2 in any major regulatory jurisdiction.

How does GHRP-2 compare to ipamorelin for longevity research?

GHRP-2 produces higher GH pulses but with significant cortisol and prolactin co-stimulation. Ipamorelin produces reliable GH pulses with minimal cortisol/prolactin effects, making it more selective and preferred for most longevity research contexts where the cortisol elevation would partially offset GH benefits.

Can GHRP-2 and GHRH analogs be combined?

Yes — the same GHRP+GHRH synergy applies. GHRP-2 combined with CJC-1295 or sermorelin produces a supraadditive GH pulse. Because GHRP-2 is already the highest-amplitude GHRP in the class, the combined pulse can be very large — which increases the cortisol co-response proportionally.

Does GHRP-2 cause water retention?

GH elevation by any secretagogue can cause water retention via IGF-1-mediated sodium reabsorption. This is a class effect of GH secretagogues, not specific to GHRP-2. The degree of water retention correlates with the magnitude of GH elevation — which makes GHRP-2 more likely to produce this effect than ipamorelin at equivalent doses.

Reviewer sign-off Reviewed 2026-04-30 by the PeptideRadar Research Desk for RUO compliance, mechanism accuracy, and citation integrity. Corrections: corrections@peptideradar.net.