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

Ipamorelin vs GHRP-6

Ipamorelin and GHRP-6 are synthetic growth hormone secretagogues that act through the ghrelin (GH secretagogue) receptor system 1,7,8. They were compared directly in animal pharmacology, where ipamorelin released GH without the ACTH and cortisol rise seen with GHRP-6 1. Neither is approved by the FDA, and both are named on WADA's 2026 Prohibited List 4,11,12.

Unbranded reference vial illustrating Ipamorelin; not an actual product
Ipamorelin
Not approved — research use only
Unbranded reference vial illustrating GHRP-6; not an actual product
GHRP-6
Not approved — research use only

Side by side

FieldIpamorelinGHRP-6
ClassPentapeptide GH secretagogue 1Hexapeptide GH-releasing peptide 5
Origin and structureSynthetic pentapeptide from Novo Nordisk's GH secretagogue program 1Synthetic hexapeptide His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 5
Proposed mechanismReleases GH through a GHRP-like receptor 1Acts on the GH secretagogue receptor, whose endogenous ligand is ghrelin 7,8
Half-lifeTerminal half-life of about 2 hours in healthy men 2Not identified in the sources reviewed
Highest human trial phasePhase 2 randomized trial in postoperative ileus (117 enrolled) 3Small physiology and diagnostic-test studies 5,6
FDA statusNot approved; FDA proposed in 2024 not to add it to the 503A bulks list; on FDA's 503B category 2 list 4,10Not approved; listed in 503A category 3 (nominated without adequate support) 11
Published human outcomesNo significant difference from placebo in time to first tolerated meal (25.3 versus 32.6 hours, p = 0.15) 3As a GH provocation test in 49 patients, GHRP-6 alone was highly specific but less sensitive than the insulin tolerance test 6
Safety signalsFDA noted more hypokalemia, insomnia and hyperglycemia and deaths of unclear relationship in the ipamorelin arm of the ileus trial 4Slight rises in prolactin and cortisol after intravenous use in 6 healthy men 5
WADA statusNamed under S2.2.4 as a GH secretagogue; prohibited at all times 12Named under S2.2.4 as a GH-releasing peptide; prohibited at all times 12
Evidence levelAnimal pharmacology, a human PK study and one phase 2 trial 1,2,3Small human endocrine and diagnostic studies plus cell data 5,6,9

Ipamorelin: what the data says

Ipamorelin is a synthetic pentapeptide that released GH from rat pituitary cells and in rats and pigs, through a GHRP-like receptor 1. In conscious swine it did not affect FSH, LH, prolactin or TSH and did not raise ACTH or cortisol beyond the levels seen after GHRH, which led its developers to call it the first selective GH secretagogue (animal data) 1. In healthy male volunteers, intravenous infusion produced a single episode of GH release peaking at 0.67 hours, and the terminal half-life was 2 hours 2.

In a randomized, placebo-controlled phase 2 trial in 117 patients after bowel resection, median time to first tolerated meal was 25.3 hours with ipamorelin and 32.6 hours with placebo (p = 0.15), and key and secondary efficacy analyses did not differ from placebo 3. FDA's 2024 review noted hypokalemia (12.5% versus 3.4%) and insomnia (10.7% versus 5.2%) more often with ipamorelin, and stated that it was unclear whether deaths in treated patients were drug-related 4.

GHRP-6: what the data says

GHRP-6 is a synthetic hexapeptide 5. Synthetic GH secretagogues act on a G protein-coupled receptor in the pituitary and hypothalamus, and the endogenous ligand of that receptor was later identified as ghrelin, a 28-amino-acid acylated peptide from the stomach 7,8. In 6 healthy men, intravenous and intranasal GHRP-6 raised plasma GH, prolactin and cortisol rose slightly after intravenous use, and IGF-I rose after repeated intranasal use 5.

In 9 adults with type 1 diabetes and 9 controls, GHRP-6 released GH, ACTH and cortisol 9. As a diagnostic test in 49 patients with suspected pituitary disease and 20 controls, GHRP-6 alone was highly specific but had limited sensitivity compared with the insulin tolerance test, and no side effects were observed during administration 6.

Key research differences

  • Stress-axis effects: in swine, GHRP-6 raised ACTH and cortisol while ipamorelin did not beyond GHRH levels (animal data) 1.
  • Size: ipamorelin is a pentapeptide and GHRP-6 a hexapeptide 1,5.
  • Clinical development: ipamorelin reached a phase 2 efficacy trial, which did not meet its endpoints, whereas GHRP-6 human data are mainly diagnostic and physiology studies 3,6.
  • Pharmacokinetics: a human terminal half-life of about 2 hours is reported for ipamorelin; none was found for GHRP-6 2.
  • FDA compounding categories differ: ipamorelin is on the 503B category 2 list, and GHRP-6 is in 503A category 3 10,11.

Where the evidence is limited

The only direct comparison identified is animal pharmacology in rats and swine 1. Human data for GHRP-6 are small, short physiology and diagnostic studies, and the single ipamorelin efficacy trial was a small proof-of-concept study in a surgical population that did not show benefit over placebo 3,5,6. Long-term human safety data were not identified for either compound.

Frequently asked questions

Do ipamorelin and GHRP-6 act on the same receptor?
Both are GH secretagogues; ipamorelin acts through a GHRP-like receptor and GHRP-6 through the GH secretagogue receptor, whose natural ligand is ghrelin 1,7,8.
Is ipamorelin more selective than GHRP-6?
In swine, ipamorelin did not raise ACTH or cortisol beyond GHRH levels, while GHRP-6 did; this is animal data 1.
Has either been tested in a clinical trial?
Ipamorelin was tested in a phase 2 postoperative ileus trial that showed no significant difference from placebo 3. GHRP-6 has been used in diagnostic GH testing 6.
What is their FDA status?
Neither is approved; FDA proposed not adding ipamorelin to the 503A bulks list and places GHRP-6 in 503A category 3 4,11.
Are they prohibited in sport?
Both are named under S2.2.4 of WADA's 2026 List and are prohibited at all times 12.

References

  1. Ipamorelin, the first selective growth hormone secretagogue European Journal of Endocrinology. 1998
  2. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers Pharmaceutical Research. 1999
  3. Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients International Journal of Colorectal Disease. 2014
  4. FDA Briefing Document: Ipamorelin-related bulk drug substances, Pharmacy Compounding Advisory Committee, October 29, 2024 FDA. 2024
  5. Intranasal administration of His-D-Trp-Ala-Trp-D-Phe-LysNH2 (growth hormone releasing peptide) increased plasma growth hormone and insulin-like growth factor-I levels in normal men Endocrinologia Japonica. 1991
  6. Diagnosis of growth hormone deficiency in adults: provocative testing with GHRP6 in comparison to the insulin tolerance test Hormone and Metabolic Research. 2009
  7. A receptor in pituitary and hypothalamus that functions in growth hormone release Science. 1996
  8. Ghrelin is a growth-hormone-releasing acylated peptide from stomach Nature. 1999
  9. 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
  10. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (content current as of 04/22/2026) FDA (Human Drug Compounding). 2026
  11. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the FD&C Act (categories 1, 2 and 3; updated May 14, 2026) FDA. 2026
  12. 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.