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Ipamorelin vs GHRP-6

Last updated: October 3, 2026 · 5 min read · By the Grey Peptides Editorial Board

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Grey Peptides
Grey Peptides Editorial Board
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Key takeaways
  • Both act on the ghrelin receptor to release growth hormone. Ipamorelin was designed to do it without the stress-hormone rise GHRP-6 causes: in pigs it did not raise ACTH or cortisol even at very high doses.
  • GHRP-6 has more human studies, mostly 1990s endocrine tests, and they show it raising cortisol and ACTH as well as growth hormone. Ipamorelin's human record is a dosing study and one failed phase 2 trial.
  • Neither is approved, both are on the FDA's list of substances raising safety concerns for outsourcing-facility compounding, and both are banned in sport.

Side by side

Ipamorelin Medium and GHRP-6 Medium belong to the growth hormone-releasing peptides, which act on the receptor ghrelin uses rather than on the GHRH receptor. WADA's 2026 List names both in section S2.2.4 among the growth hormone secretagogues 1. GHRP-6 came first; ipamorelin was developed later as a more selective alternative 2. The table is read from our encyclopedia entries.

FieldIpamorelinGHRP-6
Encyclopedia entryIpamorelin Full entryGHRP-6 Full entry
Molecule classPeptidePeptide
CategoryGrowth HormoneGrowth Hormone
FDA statusDiscontinuedResearch Chemical
Approved elsewhereNone recordedNone recorded
Evidence gradeMediumMedium
Half-life≈ 2 hours≈ 2.5 hours
FormulaC38H49N9O5C46H56N12O6
Molecular weight711.9 g/mol873.0 g/mol
WADA 2026Prohibited at all times (S2.2.4)Prohibited at all times (S2.2.4)
WADA 2027Prohibited at all times (S2.2.4)Prohibited at all times (S2.2.4)
In one lineA ghrelin-receptor agonist that released growth hormone without raising cortisol in pigs; in people it has one dosing study and a phase 2 surgery trial that found no benefit. Never approved.The original growth hormone-releasing hexapeptide: a strong, fast releaser in 1990s human tests that also raises ACTH and cortisol.
MechanismAgonist at the ghrelin (GHRP) receptor that releases growth hormone with a potency close to GHRP-6's in rat pituitary cells and animals. In pigs it did not raise ACTH or cortisol even at more than 200 times its effective dose, unlike GHRP-6 and GHRP-2; that selectivity has not been measured in a published human study. As a ghrelin mimetic it speeds gut transit in rodents.Agonist at the ghrelin receptor (GHS-R1a). A single 1 µg/kg intravenous dose releases about as much growth hormone as GHRH, and the two together several times more; the response largely depends on an intact hypothalamic-pituitary connection. GHRP-6 also raises ACTH and cortisol, unlike GHRH. In rat pituitary cells it acts through the inositol trisphosphate/diacylglycerol pathway and a rise in intracellular calcium.
Sources in the entry1517
Study cards1415
Dosage pageDosage pageDosage page

What 'selective' means

The discovery paper for ipamorelin tested it against GHRP-6 in rat pituitary cells, anaesthetised rats and conscious pigs. It released growth hormone about as potently as GHRP-6, but unlike GHRP-6 and GHRP-2 it did not raise ACTH or cortisol in the pigs, even at doses more than 200 times what it took to release growth hormone 2. GHRP-6's stress-hormone effect shows up in people: in healthy men given four overnight intravenous doses, growth hormone averaged 15.4 ng/mL against 5.5 on placebo, ACTH 21.0 against 16.6 pg/mL and cortisol 56.0 against 25.2 ng/mL 3. That difference, demonstrated head to head in animals and shown for GHRP-6 in humans, is the basis for ipamorelin's reputation. The effect can be dramatic in people whose adrenal glands do not work: in six patients with Addison's disease on replacement therapy, GHRP-6 raised ACTH from 38.1 to 174.9 pmol/L, an ACTH response about 30 times larger than in controls 4. No human study has compared ipamorelin and GHRP-6 directly.

GHRP-6 in people

GHRP-6's human studies are mostly endocrinology tests from the 1990s. It raised growth hormone when taken by mouth in short children, peaking at 60 minutes close to the response to the maximally effective intravenous dose 5. It was combined with exercise in fit young men, producing long, high-amplitude growth hormone peaks 6, and assessed as a test of pituitary reserve in children, where responses overlapped too much between deficient and normal children to diagnose individuals 7. It was never developed into a treatment. According to our entry, the FDA places GHRP-6 in 503A Category 3 and has listed it in 503B Category 2, significant safety risks, since September 29, 2023, so it cannot be compounded in the US 1.

Ipamorelin in people

Ipamorelin's human data are short. In 40 healthy men given single intravenous infusions at five doses, its kinetics were dose-proportional with a terminal half-life of about two hours 8. Its one efficacy trial, a multicentre double-blind phase 2 study in 114 adults recovering from bowel resection, found no significant benefit on the return of bowel function 9. The FDA placed ipamorelin acetate in 503B Category 2 in 2023, and its 503A nomination was withdrawn 1. Our ipamorelin vs sermorelin comparison sets it beside the GHRH analogues.

Appetite, cortisol and what users notice

Because both act on the ghrelin receptor, appetite is a plausible effect of either, and it is well documented for this class: GHRP-2, a close relative, raised food intake by 35.9% in lean men in one study 10. The cortisol and ACTH rise with GHRP-6 3 is the clearer difference between the two compounds. Neither has long-term human safety data, and neither has been tested for the body-composition or anti-ageing uses it is sold for online.

How the differences add up (as of October 3, 2026)

GHRP-6 has the longer human record and the clearer stress-hormone effect; ipamorelin has the cleaner profile in animals, a dosing study and a failed phase 2 trial. Neither is approved, both are restricted for compounding, and both are prohibited in sport 1. Doses on this page are those in our entries' sources, not recommendations.

Frequently asked questions

Is ipamorelin better than GHRP-6?

It is more selective in animal studies, releasing growth hormone without raising ACTH or cortisol, which GHRP-6 does in people. No human trial has compared them, and neither is approved.

Does GHRP-6 raise cortisol?

Yes. In healthy men, overnight intravenous GHRP-6 raised cortisol to 56.0 ng/mL against 25.2 on placebo, along with ACTH and growth hormone.

Can ipamorelin or GHRP-6 be compounded in the US?

No. The FDA lists both in 503B Category 2, and GHRP-6 is in 503A Category 3; ipamorelin's 503A nomination was withdrawn.

Sources

  1. Grey Peptides dataset records for both compounds (status, half-life and studied doses as sourced on each entry); read October 2, 2026.
  2. Raun, K., et al. (1998). Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol, 139(5), 552-61. PMID: 9849822
  3. Frieboes, R. M., et al. (1995). Growth hormone-releasing peptide-6 stimulates sleep, growth hormone, ACTH and cortisol release in normal man. Neuroendocrinology, 61(5), 584-9. PMID: 7617137
  4. Martins, M. R., et al. (2003). GH-releasing peptide (GHRP-6)-induced ACTH release in patients with addison's disease: effect of glucocorticoid withdrawal. J Endocrinol Invest, 26(2), 143-7. PMID: 12739742
  5. Bellone, J., et al. (1995). Growth hormone-releasing effect of oral growth hormone-releasing peptide 6 (GHRP-6) administration in children with short stature. Eur J Endocrinol, 133(4), 425-9. PMID: 7581965
  6. Nooitgedagt, A., et al. (1997). Influence of endogenous cholinergic tone and growth hormone-releasing peptide-6 on exercise induced growth hormone release. Clin Endocrinol (Oxf), 46(2), 195-202. PMID: 9135702
  7. Pombo, M., et al. (1996). Growth hormone releasing hexapeptide-6 (GHRP-6) test in the diagnosis of GH-deficiency. J Pediatr Endocrinol Metab, 9 Suppl 3, 333-8. PMID: 8887178
  8. Gobburu, J. V., et al. (1999). Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res, 16(9), 1412-6. PMID: 10496658
  9. Beck, D. E., et al. (2014). Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis, 29(12), 1527-34. PMID: 25331030
  10. Laferrère, B., et al. (2005). Growth hormone releasing peptide-2 (GHRP-2), like ghrelin, increases food intake in healthy men. J Clin Endocrinol Metab, 90(2), 611-4. PMID: 15699539

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.

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