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Hexarelin vs Ipamorelin: Evidence, Selectivity & Safety Compared

Hexarelin and ipamorelin both release growth hormone through the ghrelin receptor. Hexarelin is a potent GHRP-6 relative that also raises ACTH, cortisol and prolactin in people; ipamorelin was designed to be more selective for GH. Neither is FDA-approved, and no study has compared them directly.

Unapproved Unapproved No head-to-head human trial
Comparison banner for hexarelin and ipamorelin, two growth hormone secretagogues that differ in hormonal selectivity.
Hexarelin and ipamorelin share the ghrelin receptor but differ in how much they affect ACTH, cortisol and prolactin. Illustration © Inside Peptides.
Evidence-Based Short Answer

Evidence-Based Summary

Hexarelin (examorelin) and ipamorelin are synthetic peptides that release growth hormone through the ghrelin receptor (GHS-R1a). Human studies show hexarelin is not selective: a single administration raised ACTH and cortisol about as much as the stress hormone CRH, and it also raises prolactin. Its GH effect partly faded during 16 weeks of repeated use. Ipamorelin was developed to avoid the ACTH and cortisol rise, which its developers showed in swine; human data are limited to a pharmacology study and a negative Phase 2 bowel-surgery trial. Hexarelin's small heart-function studies are exploratory. No study has compared the two directly, neither is FDA-approved, and both are banned in sport. Ipamorelin is on FDA's compounding safety list; hexarelin is not listed in FDA's bulk-substance categories.

Inside Peptides provides educational, evidence-first analysis, not medical advice. Neither hexarelin nor ipamorelin is an FDA-approved medicine, and this page gives no dosing or sourcing information.
At a Glance

Quick Comparison: Hexarelin vs Ipamorelin

A high-level comparison of molecule class, molecular receptor targets, FDA regulatory approvals, and verified clinical programs.

Table 1: Verified regulatory, pharmacological, and clinical comparison between Hexarelin and Ipamorelin.
Feature Hexarelin Ipamorelin
Class Synthetic hexapeptide GHRP; a GHRP-6 analogue Synthetic pentapeptide GH secretagogue
Target receptor GHS-R1a (ghrelin receptor); possible direct heart actions proposed GHS-R1a (ghrelin receptor)
Effects beyond GH Raises ACTH, cortisol and prolactin in people Little ACTH or cortisol effect in swine (animal finding)
How it has been given in studies Single intravenous administrations; repeated injections under the skin in a 16-week study Intravenous infusions in human pharmacology and bowel-surgery trials
U.S. regulatory status Not FDA-approved; not in FDA's 503A/503B bulk categories as of October 2026 Not FDA-approved; FDA 503B category 2
Strongest human evidence Small endocrine and acute heart-function studies; tolerance over 16 weeks Phase 2 bowel-surgery RCT (114 patients) missed its efficacy endpoint
Main safety concerns Cortisol and prolactin rises; fading GH response with repeated use FDA cites serious adverse events including death with intravenous use
WADA status (2026) Prohibited at all times, class S2 (named as examorelin) Prohibited at all times, class S2
Receptor Pharmacology

Potency Versus Selectivity at the Ghrelin Receptor

Both peptides activate GHS-R1a, the receptor cloned in 1996 and later shown to respond to ghrelin. They differ mainly in what else they stimulate.

Hexarelin Target

Hexarelin

Primary Target: GHS-R1a (ghrelin receptor)

Affinity Profile: Potent GH secretagogue; not selective for GH

In people, hexarelin and GHRP-2 produced similar strong GH responses along with rises in prolactin, ACTH and cortisol. Heart-function changes in people who released little GH led researchers to propose GH-independent heart actions, supported by rat studies but unproven in patients.

Ipamorelin Target

Ipamorelin

Primary Targets: GHS-R1a (ghrelin receptor)

Affinity Profile: GH release comparable to GHRP-6 in animals, with little ACTH or cortisol effect

Developer experiments in swine found no meaningful ACTH or cortisol rise even at very high doses relative to the GH-releasing dose, unlike GHRP-6 and GHRP-2. Hexarelin was not included in that comparison.

Regulatory Status

FDA and Anti-Doping Status

United States status checked 11 October 2026.

Unapproved

Hexarelin Status & Formulations

Not FDA-approved and never marketed as a medicine in the U.S. Hexarelin does not appear in FDA's 503A or 503B bulk-substance category lists reviewed for this page, which means FDA has not published a specific safety assessment; it does not mean it is approved or safe. WADA class S2 (examorelin/hexarelin).

Unapproved

Ipamorelin Status & Formulations

Not FDA-approved. FDA 503B category 2 since September 29, 2023, citing immunogenicity and impurity concerns and a published report of serious adverse events including death with intravenous use for gut motility. WADA class S2.

Critical Regulatory Distinction

Absence from an FDA safety list is not evidence of safety. Neither peptide is an approved medicine, and products sold online as 'research peptides' are not regulated drugs.

Human Evidence

1990s Endocrine Studies vs a Modern Phase 2 Trial

Hexarelin's human data come from small 1990s hormone and heart studies. Ipamorelin's come from a pharmacology study and Phase 2 trials in surgery patients.

Hexarelin: Clinical Evidence Overview

In 12 healthy adults, a single intravenous administration raised ACTH and cortisol about as much as CRH, with larger responses in Cushing's disease. In six young volunteers it matched GHRP-2 for GH release and raised prolactin, ACTH and cortisol. A 16-week study found the GH response partly faded and recovered after stopping, with no significant change in IGF-I, body composition or bone density. Acute studies in 16 men and 13 heart-failure patients found short rises in ejection fraction, which remain exploratory.

Ipamorelin: Clinical Evidence Overview

In healthy men, intravenous infusions produced a single GH pulse with a half-life of about two hours. A Phase 2 double-blind trial in 114 bowel-resection patients found it well tolerated but not significantly better than placebo for time to first tolerated meal (25.3 vs 32.6 hours, p = 0.15). A larger second Phase 2 trial (320 enrolled, registry record in References) is listed as completed without posted results.

Evidence Matrix

Curated Clinical Evidence Table

A curated selection of the primary studies behind each compound’s evidence profile. Results from different studies are not directly comparable.

Table 3: Key studies evaluating Hexarelin and Ipamorelin.
Study & Citation Population Comparison & Dosing Duration Main Endpoint Key Finding Methodological Limitations
Ghigo et al., 1997 (hexarelin) 12 healthy adults and 17 with Cushing's syndrome Hexarelin vs CRH Single administration ACTH and cortisol Hexarelin raised ACTH and cortisol about as much as CRH in healthy adults. Hormone study; no clinical outcome.
Arvat et al., 1997 (hexarelin vs GHRP-2) 6 young and 6 elderly volunteers Hexarelin vs GHRP-2, GHRH, TRH and CRH Single administrations GH, prolactin, ACTH, cortisol Hexarelin and GHRP-2 gave similar GH responses and similar prolactin, ACTH and cortisol rises. Very small; ipamorelin not studied.
Rahim et al., 1998 (hexarelin) Adults (number not given in the abstract) Repeated use over 16 weeks 16 weeks GH response, IGF-I, body composition GH response partly faded and recovered after stopping; no significant change in IGF-I or body composition. Small study; tolerance limits any long-term use case.
Imazio et al., 2002 (hexarelin) 13 patients with severe heart failure Hexarelin, compared with earlier control groups Single administration Ejection fraction Ejection fraction rose in ischemic but not dilated cardiomyopathy. Tiny, acute and not randomized.
Beck et al., 2014 (ipamorelin, NCT00672074) 114 adults after bowel resection Ipamorelin vs placebo Up to 7 days Time to first tolerated meal No significant difference (p = 0.15). Small proof-of-concept trial.
Gobburu et al., 1999 (ipamorelin) Healthy male volunteers Escalating intravenous infusions Single administrations Pharmacokinetics and GH Single GH pulse; half-life about 2 hours. Did not measure cortisol selectivity against another GHRP.
Safety & Tolerability

What Is Known About Safety

None of these compounds has the long-term, large-scale safety data that come with an approved medicine. What is known comes from short hormone studies, small trials and FDA's compounding review.

Safety Assessment

Different FDA positions, same lack of approval

FDA names ipamorelin acetate as a compounding substance that may present significant safety risks. Hexarelin is not on that list, but it has never been approved, and its human safety data come from small, short 1990s studies.

Table 4: Evidence-supported safety considerations and adverse-reaction frequency for Hexarelin and Ipamorelin.
Safety Consideration Hexarelin Ipamorelin
ACTH and cortisol Raised in people, comparable to CRH Not raised in swine; limited human data
Prolactin Raised in people Not raised in swine
Repeated use GH response partly fades over 16 weeks No long-term human data
Serious adverse events None highlighted in small studies; data are sparse FDA cites a report of serious adverse events including death with intravenous use
Pharmacological Commonalities

What Hexarelin and Ipamorelin Have in Common

Where the two compounds overlap in biology, evidence or regulatory context.

Ghrelin-receptor agonists

Both release GH by activating GHS-R1a.

No approved use

Neither is an approved medicine in the U.S., and neither has shown a treatment benefit in a controlled trial.

Banned in sport

Both are named in WADA's 2026 class S2.

Distinguishing Features

Key Scientific & Clinical Differences

Meaningful distinctions in mechanism, strength of evidence, safety and regulatory status.

Hormonal selectivity

Hexarelin raises ACTH, cortisol and prolactin in people; ipamorelin was shown to spare ACTH and cortisol in animals.

Tolerance

Hexarelin's GH effect partly faded with repeated use; no comparable data exist for ipamorelin.

FDA compounding list

Ipamorelin is in 503B category 2; hexarelin is not in FDA's bulk categories.

Inside Peptides Editorial Policy

Scientific Comparison vs Clinical Recommendations

Inside Peptides compares scientific evidence, receptor pharmacology, and official regulatory documents to advance public and professional understanding. We do not determine which compound is appropriate for an individual patient, rank medications with arbitrary scores, or recommend initiating or switching treatments.

Decisions about any medicine require a licensed healthcare professional who can weigh personal medical history, contraindications, interactions and monitoring needs. Unapproved peptides have no established safe use, and products sold as “research chemicals” are not the preparations studied in clinical research.

Evidence Verification

Approved Uses vs Online Claims

A critical scientific distinction between verified, FDA-approved clinical uses and unverified claims circulating on social media and vendor platforms.

Hexarelin protects or repairs the heart

Unproven
Regulatory Context:

Not FDA-approved for any use.

Scientific Reality:

Short ejection-fraction rises in tiny single-administration studies and rat infarction models do not show that it treats heart disease. No outcome trial exists.

Ipamorelin gives GH benefits without any hormonal side effects

Partly supported
Regulatory Context:

On FDA's compounding safety list; WADA S2.

Scientific Reality:

Its cortisol-sparing selectivity comes from animal experiments. Human safety data are limited and FDA cites serious adverse events with intravenous use.

Claim-Level Certainty

Evidence Strength Across Clinical Domains

Inside Peptides evaluates scientific certainty at the claim level. Because clinical evidence varies significantly depending on the therapeutic endpoint evaluated, each domain is assessed independently.

Acute GH release in people

Both cause short GH pulses in small human studies.

Hexarelin: Early Human Evidence
Ipamorelin: Early Human Evidence

Heart function

Hexarelin has small acute human studies only; ipamorelin has not been studied for this.

Hexarelin: Early Human Evidence
Ipamorelin: Insufficient Evidence

Any clinical treatment benefit

No controlled trial shows benefit for either; ipamorelin's Phase 2 trial was negative.

Hexarelin: Insufficient Evidence
Ipamorelin: Insufficient Evidence
Unresolved Questions

What Research Still Doesn’t Tell Us

Identifying open scientific questions, pending active-comparator trials, and areas where long-term clinical data remain incomplete.

No direct comparison

Hexarelin and ipamorelin have never been compared in the same study, human or animal, in the sources we reviewed.

Human selectivity of ipamorelin

The cortisol-sparing profile needs confirmation in controlled human studies.

Heart claims

Hexarelin's proposed heart effects have not been tested in outcome trials.

Related Compound Profiles

Individual profiles provide full molecular datasheets, CAS numbers, preclinical histories, and compound monographs.

Bibliography & Sources

Scientific & Regulatory References

Every pharmacological mechanism, clinical trial result, and regulatory approval cited on this page is traceable to official FDA prescribing documentation, ClinicalTrials.gov registries, or peer-reviewed medical publications.

  1. Human endocrine study
    Adrenocorticotropin- and cortisol-releasing effect of hexarelin, a synthetic growth hormone-releasing peptide, in normal subjects and patients with Cushing's syndrome.
    Ghigo E et al. (1997) · J Clin Endocrinol Metab.
    Direct Source DOI: 10.1210/jcem.82.8.4132 PubMed: 9253314
  2. Human endocrine study
    Effects of GHRP-2 and hexarelin, two synthetic GH-releasing peptides, on GH, prolactin, ACTH and cortisol levels in man. Comparison with the effects of GHRH, TRH and hCRH.
    Arvat E et al. (1997) · Peptides.
    Six young and six elderly volunteers; single administrations.
    Direct Source DOI: 10.1016/s0196-9781(97)00016-8 PubMed: 9285939
  3. Human 16-week study
    Growth hormone status during long-term hexarelin therapy.
    Rahim A et al. (1998) · J Clin Endocrinol Metab.
    Direct Source DOI: 10.1210/jcem.83.5.4812 PubMed: 9589671
  4. Human acute cardiac study
    Cardiac effects of hexarelin in hypopituitary adults.
    Bisi G et al. (1999) · Eur J Pharmacol.
    Direct Source DOI: 10.1016/s0014-2999(99)00537-3 PubMed: 10528131
  5. Human acute cardiac study
    GH-independent cardiotropic activities of hexarelin in patients with severe left ventricular dysfunction due to dilated and ischemic cardiomyopathy.
    Imazio M et al. (2002) · Eur J Heart Fail.
    Direct Source DOI: 10.1016/s1388-9842(01)00223-9 PubMed: 11959048
  6. Discovery pharmacology (rat cells, rats, swine)
    Ipamorelin, the first selective growth hormone secretagogue.
    Raun K et al. (1998) · Eur J Endocrinol.
    Animal and cell work by Novo Nordisk scientists; compares ipamorelin with GHRP-6 and GHRP-2 in the same experiments.
    Direct Source DOI: 10.1530/eje.0.1390552 PubMed: 9849822
  7. Human pharmacokinetic/pharmacodynamic study
    Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers.
    Gobburu JV et al. (1999) · Pharm Res.
    Direct Source DOI: 10.1023/a:1018955126402 PubMed: 10496658
  8. Phase 2 randomized placebo-controlled trial
    Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients.
    Beck DE et al. (2014) · Int J Colorectal Dis.
    Sponsored by Helsinn Therapeutics; see the trial registry record in References.
    Direct Source DOI: 10.1007/s00384-014-2030-8 PubMed: 25331030
  9. Trial registry record
    Safety and Efficacy of Ipamorelin for Management of Post-Operative Ileus
    ClinicalTrials.gov (NCT00672074; Helsinn Therapeutics) (2017).
    Phase 2; Completed; 117 enrolled (actual); no results posted on the registry. Checked 11 October 2026.
    Direct Source
  10. Trial registry record
    Safety and Efficacy of Ipamorelin Compared to Placebo for the Recovery of Gastrointestinal Function
    ClinicalTrials.gov (NCT01280344; Helsinn Therapeutics) (2017).
    Phase 2; Completed; 320 enrolled (actual); no results posted on the registry and no matching publication found. Checked 11 October 2026.
    Direct Source
  11. Receptor cloning study
    A receptor in pituitary and hypothalamus that functions in growth hormone release.
    Howard AD et al. (1996) · Science.
    Direct Source DOI: 10.1126/science.273.5277.974 PubMed: 8688086
  12. FDA compounding safety list
    Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks
    U.S. Food and Drug Administration (2026).
    Page content current as of 22 April 2026; checked 11 October 2026.
    Direct Source
  13. Anti-doping rule
    World Anti-Doping Code International Standard: Prohibited List 2026
    World Anti-Doping Agency (2026).
    Direct Source