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For research use only. Not for human or veterinary use. Not a drug, food, or dietary supplement.
AMIRAVOResearch Library

GHRP-2 vs GHRP-6

GHRP-2 and GHRP-6 are synthetic growth hormone-releasing peptides from the same pharmacological family; both are thought to act through the growth hormone secretagogue (ghrelin) receptor 1,3. They differ in potency and efficacy in animal pharmacology, in the human and animal studies available, and in the concerns the FDA lists for each 2,9. Neither is an approved medicine in the sources reviewed, and both are named on WADA's 2026 Prohibited List 9,10.

Unbranded reference vial illustrating GHRP-2; not an actual product
GHRP-2
Approved outside the US
Unbranded reference vial illustrating GHRP-6; not an actual product
GHRP-6
Not approved — research use only

Side by side

FieldGHRP-2GHRP-6
ClassSynthetic GH-releasing peptide; ghrelin-receptor agonist 3Synthetic GH-releasing hexapeptide that acts on the ghrelin-receptor system 1,8
Origin and structureUnnatural (synthetic) GHRP; the FDA notes it contains an unnatural amino acid that complicates characterization 1,9Unnatural (synthetic) GHRP 1
Proposed mechanismBinds the GH secretagogue receptor, stimulating GH release and, in humans, appetite 3Stimulates GH release; like ghrelin, it also raised ACTH and cortisol in human studies 5
Half-lifeNot identified in the sources reviewedNot identified in the sources reviewed
Highest human trial phaseSmall physiology studies and diagnostic-test studies in humans 3,4Small physiology studies; as a component of a combination with EGF, a phase 3 open-label stroke trial 5,8
FDA statusListed by the FDA among bulk substances for compounding that may present significant safety risks (injectable and nasal routes) 9Listed on the same FDA page, with limited safety information 9
Published human outcomesIn 7 lean men, intake at a buffet meal was 35.9% higher during infusion than with saline, and serum GH rose 3. In 36 patients, the ACTH response in a GHRP-2 test helped identify secondary adrenal insufficiency 4In 9 adults with type 1 diabetes and 9 controls, GHRP-6 released GH, ACTH and cortisol, with responses similar between groups and a smaller GH response than ghrelin 5. In a phase 3 stroke trial of EGF plus GHRP-6 (188 patients), the primary endpoint was missed 8
Safety signalsFDA is aware of reports of increased insulin requirement, death of critically ill study subjects, infection and pancreatitis, though causality has not been established 9FDA cites potential effects on cortisol and increased blood glucose from decreased insulin sensitivity 9
WADA statusNamed under S2.2.4 as GHRP-2 (pralmorelin); prohibited at all times 10Named under S2.2.4 as GHRP-6; prohibited at all times 10
Evidence levelSmall human physiology studies plus animal and cell data 3,4,6Small human physiology studies, a combination-product trial and animal data 5,7,8

GHRP-2: what the data says

In healthy men, GHRP-2 behaved like ghrelin on appetite: in a small comparison of 7 lean men, intake at an ad libitum buffet was 35.9% higher during GHRP-2 infusion than with saline, and serum GH rose significantly 3. A study from a Japanese university clinic of 36 patients with hypothalamic-pituitary disorders described the GHRP-2 test as widely used for diagnosing GH deficiency and found that the ACTH response in the test had 83% sensitivity and 88% specificity for secondary adrenal insufficiency at a chosen cutoff 4.

In animal and cell work, GHRP-2 reduced markers of M1 macrophage polarization in vitro and was associated with higher biomechanical and histologic scores in a rat rotator cuff tear model (animal-only evidence) 6. In swine (animal data), GHRP-2 showed higher potency but lower maximal GH-releasing efficacy than GHRP-6, and it raised ACTH and cortisol 2.

GHRP-6: what the data says

In humans, GHRP-6 has mostly been studied in endocrine physiology 5. In 9 patients with type 1 diabetes and 9 control subjects, GHRP-6 released GH, ACTH and cortisol, GH release was larger after ghrelin than after GHRP-6, and the ACTH and cortisol responses were similar between patients and controls 5. In swine (animal data), GHRP-6 raised ACTH and cortisol 2.

A 2026 phase 3 open-label trial in 188 patients with acute ischemic stroke tested EGF combined with GHRP-6 against standard care; it missed its primary endpoint, and an analysis of 27 patients with severe stroke reported lower disability and mortality risk in the treated group 8. Because the intervention was a combination and the subgroup finding was exploratory, it cannot be attributed to GHRP-6 alone 8. In a mouse model of lung injury (animal-only evidence), GHRP-6 was associated with less neutrophilic alveolitis and less collagen accumulation 7.

Key research differences

  • Potency and efficacy: in swine, GHRP-2 showed higher potency but lower maximal efficacy than GHRP-6 for GH release (animal data) 2.
  • Stress-axis effects: both raised ACTH and cortisol in swine 2; in humans, GHRP-6 raised ACTH and cortisol 5 and the ACTH response to GHRP-2 is used as a diagnostic readout 4.
  • Appetite: increased food intake has been documented in a small human study of GHRP-2 3. No equivalent human feeding study of GHRP-6 was identified.
  • Clinical-trial evidence: GHRP-6 appears in a phase 3 combination trial with EGF in stroke that missed its primary endpoint 8, whereas GHRP-2 is documented mainly as a diagnostic test in humans 4.
  • FDA-cited concerns differ: for GHRP-2, serious adverse event reports of unestablished causality; for GHRP-6, effects on cortisol and blood glucose 9.
  • Both are named in WADA class S2.2.4 and are prohibited at all times 10.

Where the evidence is limited

Evidence for both compounds is limited 2,8. No head-to-head human trial was identified, and the direct comparisons available are animal pharmacology 2. The human GHRP-2 and GHRP-6 studies are small physiology or diagnostic studies, and the only trial of GHRP-6 in patients tested a combination product 3,4,5,8. No half-life figure for either compound was found in the sources reviewed. The FDA notes that causality for the adverse event reports it cites for GHRP-2 has not been established 9.

Frequently asked questions

Do GHRP-2 and GHRP-6 act on the same receptor?
Both are described as synthetic agonists of the ghrelin (GH secretagogue) receptor and are thought to share receptor and cellular mechanisms 1,3.
Have they been compared directly?
In swine (animal data), GHRP-2 had higher potency but lower efficacy than GHRP-6 for GH release, and both raised ACTH and cortisol 2. No head-to-head human trial was identified.
Has GHRP-6 been tested in a clinical trial?
A 2026 phase 3 trial tested EGF combined with GHRP-6 in acute ischemic stroke and missed its primary endpoint; a subgroup analysis in severe stroke was exploratory 8.
What does the FDA say about them?
The FDA lists both among bulk substances for compounding that may present significant safety risks, citing serious adverse event reports of unestablished causality for GHRP-2 and cortisol and blood-glucose effects for GHRP-6 9.
Are they prohibited in sport?
WADA's 2026 Prohibited List names GHRP-2 (pralmorelin) and GHRP-6 under S2.2.4, and both are prohibited at all times 10.

References

  1. History to the discovery of ghrelin Methods in Enzymology. 2012
  2. Ipamorelin, the first selective growth hormone secretagogue European Journal of Endocrinology. 1998
  3. Growth hormone releasing peptide-2 (GHRP-2), like ghrelin, increases food intake in healthy men Journal of Clinical Endocrinology & Metabolism. 2005
  4. Clinical Usefulness of the Growth Hormone-Releasing Peptide-2 Test for Hypothalamic-Pituitary Disorder Journal of the Endocrine Society. 2022
  5. Effects of ghrelin, growth hormone-releasing peptide-6, and growth hormone-releasing hormone on growth hormone, adrenocorticotropic hormone, and cortisol release in type 1 diabetes mellitus Metabolism. 2010
  6. Growth Hormone-Releasing Peptide 2 May Be Associated With Decreased M1 Macrophage Production and Increased Histologic and Biomechanical Tendon-Bone Healing Properties in a Rat Rotator Cuff Tear Model Arthroscopy. 2025
  7. Growth hormone releasing peptide-6 (GHRP-6) ameliorates acute lung injury and its subsequent evolvement to interstitial fibrosis International Immunopharmacology. 2026
  8. Phase III Open-Label, Randomized Clinical Trial of Epidermal Growth Factor and Growth Hormone Releasing Hexapeptide in Acute Ischemic Stroke Journal of Clinical Neuroscience. 2026
  9. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (Category 2; content current as of 04/22/2026) FDA (Human Drug Compounding). 2026
  10. International Standard: Prohibited List 2026 WADA. 2026

For research use only. Not for human or veterinary use. Not a drug, food, or dietary supplement. This page compares published research and is not medical advice or a recommendation.