NOT FDA-APPROVED

Hexarelin

Older GHRP · cardiac-research niche · largely replaced by Ipamorelin

An older GHRP, mostly displaced by Ipamorelin in modern stacks. Strongest acute GH pulse in the GHRP family, paired with the most pronounced prolactin elevation and a tachyphylaxis problem (effects fade with chronic use). Has direct cardiac receptor activity that's unique among GHRPs, which is the main reason it still gets attention in heart-failure research.

The 30-second read

Hexarelin is the third member of the older GHRP family alongside GHRP-2 and GHRP-6. Acutely, it produces the largest GH pulse, about 2 to 3 times higher than GHRP-2 at standard doses. The catches are real and well-characterized: the strongest prolactin elevation of any GHRP, tachyphylaxis (the effect fades with chronic use as receptors desensitize), and direct activity at the CD36 receptor in cardiac tissue. The CD36 activity is the unusual piece, it produced cardioprotective signals in animal heart-injury models, sparking research that hasn't translated into approved clinical use. Not FDA-approved. On the FDA's Category 2 list as of September 2023. In modern protocols, Hexarelin is uncommon. Ipamorelin's cleaner profile or Sermorelin's regulatory history are typically preferred.

Why this peptide is on people's radar

Hexarelin is the GHRP that makes the biggest acute GH pulse and the most pronounced collateral side-effects. It was developed in the 1990s and early studies positioned it as the most potent member of the class. The pharmacological story is genuinely interesting: Hexarelin produces measurably larger GH responses than GHRP-2 or GHRP-6 at comparable doses, particularly with single-dose administration. That sounds like an advantage until you map the rest of the profile.

Three things keep Hexarelin from being a default choice. First, prolactin elevation is more pronounced than with any other GHRP, clinically meaningful for people whose mood, libido, or breast-tissue health are affected by prolactin shifts. Second, tachyphylaxis: with chronic use, the GH-release effect diminishes as receptors desensitize. The acute potency advantage doesn't carry over into long-term protocols the way Ipamorelin's effect does. Third, direct activity at the CD36 receptor in cardiac and adipose tissue introduces effects beyond the GH-release pathway that aren't well-characterized for chronic use.

The CD36 piece is the unusual feature. Animal studies report cardioprotective effects after ischemic injury in heart-failure models, preserved cardiac function, reduced infarct size, modulation of cardiac fatty-acid metabolism. That drove a wave of cardiology research in the early 2000s that hasn't translated into approved clinical use, but is a meaningful piece of the molecule's story. For people who have heard of Hexarelin in a cardiology research context, that's where it's coming from.

What people are usually trying to do with it

People exploring Hexarelin are usually focused on:

The strongest acute GH pulse available among the GHRPs
Following the cardiology / cardioprotection research signal
Acute use cases (single-dose stimulation rather than chronic protocols)
An older option with extensive clinical literature behind it
Combinations with a GHRH analog where they specifically want the largest possible GH pulse

What the science actually shows

Hexarelin has decades of human and animal research behind it. Plain-English summary:

Largest acute GH pulse among GHRPs

Multiple studies in healthy adults confirm Hexarelin produces a larger GH pulse than GHRP-2 or GHRP-6 at standard doses, about 2 to 3 times higher in some comparisons. The acute potency advantage is real.1

Prolactin elevation

Studies confirm Hexarelin raises prolactin meaningfully, more than other GHRPs at comparable doses. Effect is dose-dependent.2

Tachyphylaxis with chronic use

The GH-release effect of repeated Hexarelin dosing diminishes over weeks of continuous administration as ghrelin receptors desensitize. The acute potency advantage doesn't carry over to chronic protocols.3

CD36 cardiac activity (preclinical)

Animal heart-injury models, myocardial infarction, ischemia-reperfusion injury, report cardioprotective effects: preserved cardiac function, reduced infarct size, modulation of cardiac fatty-acid metabolism. The CD36-binding activity is the proposed mechanism. Has not advanced to approved clinical cardiology use.4

What hasn't been demonstrated

FDA approval. Long-term safety with chronic use given the receptor-desensitization picture. That the acute potency advantage translates into better real-world outcomes for sleep, body composition, or recovery. Translation of the cardioprotective signal into approved clinical cardiology applications.

The honest read

What's solid:

Hexarelin's acute pharmacology is well-characterized. Largest GH pulse in the class is real. The CD36 cardiac activity is a real, biologically distinct feature, not just marketing. Decades of clinical research history.

What's still being worked out:

Whether Hexarelin has any advantage over Ipamorelin in chronic use, given the tachyphylaxis. Whether the CD36 cardiac signal will ever lead to approved clinical applications (it hasn't yet, despite 20+ years of preclinical work). Long-term safety with adult anti-aging-style protocols.

What's hyped beyond the evidence:

"Strongest GHRP therefore best" framings. The prolactin trade-off is real; the tachyphylaxis is real; chronic use mostly doesn't preserve the acute advantage. For most modern peptide-research goals, Hexarelin is not a sensible default. Cardioprotection claims framed as established clinical use also overstate where the evidence actually sits, the data is animal-model, not approved-indication.

Things to know if you're looking into it

Tachyphylaxis is the practical issue: the receptor-desensitization picture means Hexarelin protocols typically use shorter cycles (4–6 weeks) with longer breaks, rather than the 8–12 week cycles common with Ipamorelin. The acute potency comes with that real planning constraint.
Prolactin caveat: stronger here than with any other GHRP. People with prolactin-related health concerns should choose Ipamorelin.
CD36 cardiac activity: the unusual mechanistic feature. Doesn't translate into approved cardiology use, but is part of the molecule's story.
Athlete bans: Hexarelin is on the World Anti-Doping Agency banned list. Competitive athletes will test positive.
Regulatory status: not FDA-approved. On the FDA's Category 2 list as of September 2023.
How it's used in research: typically a small subcutaneous injection at night before bed, on an empty stomach. Some protocols use 2–3x daily.
Specific dosing protocols, mechanism, and the full reference list: all in the "Want to go deeper?" section below.

What people often ask

How is Hexarelin different from GHRP-2 and GHRP-6?

Same general class. Hexarelin is the most potent acutely (largest GH pulse), has the strongest prolactin elevation, has tachyphylaxis with chronic use, and has unique direct activity at the CD36 receptor in cardiac tissue. The other GHRPs don't share that CD36 feature.

What does "tachyphylaxis" mean?

The drug effect diminishes with repeated use as receptors desensitize. With Hexarelin, the GH-release effect drops off over weeks of continuous use, the acute potency doesn't sustain. Most other GHRPs maintain their effects better with chronic use.

What is CD36 receptor activity?

CD36 is a receptor present in cardiac and adipose tissue, involved in fatty-acid uptake and signaling. Hexarelin (uniquely among GHRPs) binds it directly, which produced cardioprotective effects in animal heart-injury models. Whether that translates to humans hasn't been established in approved clinical applications.

Should I use Hexarelin instead of Ipamorelin?

Probably not, for most goals. Ipamorelin produces a smaller acute pulse but maintains the effect with chronic use, has cleaner side effects, and matches modern peptide-research protocols better. Hexarelin makes sense for specific acute use cases or for someone interested in the cardiology research signal.

Is it FDA-approved?

No. Not approved for any indication. On the FDA's Category 2 list as of September 2023.

Does it help with heart conditions?

Animal data is suggestive. Human evidence in approved cardiology applications doesn't exist. Anyone with heart disease should be working with a cardiologist using FDA-approved treatments. Hexarelin's cardioprotective signal hasn't reached approved clinical use.

Will I test positive on a drug test?

Yes. Hexarelin is on the WADA banned list. Competitive athletes will test positive.

FDA and regulatory status

Status as of May 5, 2026: Not FDA-approved for any medical indication. On the FDA's Category 2 list as of September 2023, restricting compounding-pharmacy access under standard pathways. The April 2026 FDA advisory-committee review of compounded peptides included Hexarelin in scope. Status updates land here when they happen.

Want to go deeper? Mechanism, the CD36 cardiac story, dosing, side-effect profile, and references.

Background

Hexarelin is a synthetic hexapeptide growth-hormone secretagogue. Chemical name His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH₂ (a methylation modification distinguishes it from GHRP-6's structure). Developed in the 1990s as a more potent analog within the GHRP family. Never FDA-approved. Sold as a research peptide and used in compounded preparations through licensed pharmacies until the September 2023 Category 2 listing restricted that pathway.

Mechanism of action

GHS-R / ghrelin receptor agonism

Like other GHRPs, Hexarelin binds the GHS-R1a receptor on pituitary somatotrophs to trigger GH release. The acute pulse is larger than other GHRPs at comparable doses.

CD36 receptor activity (unique among GHRPs)

Hexarelin uniquely binds the CD36 scavenger receptor in cardiac and adipose tissue. This direct cardiac activity is the basis for the cardioprotective signal in animal heart-injury models, modulating cardiac fatty-acid metabolism, reducing infarct size in ischemia-reperfusion models, preserving cardiac function under stress.

Tachyphylaxis

With chronic dosing, the GH-release response to Hexarelin diminishes as ghrelin-receptor signaling desensitizes. Other GHRPs (especially Ipamorelin) maintain their effect better. The practical implication is that Hexarelin protocols typically use shorter cycles with breaks rather than continuous long-term use.

Prolactin elevation

The most pronounced prolactin elevation of any GHRP at comparable doses. Effect is dose-dependent.

Half-life

Plasma half-life is approximately 30–60 minutes. The GH-pulse window after dosing is roughly 1 to 2 hours.

Commonly studied dosing protocols

These are not recommendations. Always consult a licensed healthcare provider before any clinical decision.

Subcutaneous (research-community range): 100 to 300 mcg per dose, typically once nightly before bed on an empty stomach. Some protocols use 2–3x daily dosing.

Stacked with a GHRH analog: commonly paired with Sermorelin or CJC-1295 (No DAC).

Cycle length: typical research-community protocols use 4 to 6 week cycles (shorter than Ipamorelin or other GHRPs) to manage tachyphylaxis, with several weeks off between cycles.

Side effects and safety profile

Reported in clinical trials and research-community use:

Mild flushing or warmth shortly after injection (common, transient)
Injection-site redness or tenderness (common, mild)
Increased appetite (common, less than GHRP-6)
Brief lightheadedness (uncommon)
Mild fluid retention (uncommon)
Notable cortisol elevation (dose-dependent)
Pronounced prolactin elevation (dose-dependent, the largest of any GHRP)
Mood, libido, or breast-tissue concerns related to prolactin shifts
Effect diminution over weeks (tachyphylaxis)

Theoretical concerns: GH/IGF-1 elevation interacts theoretically with cancer biology, avoid in active malignancy. Cautious use in diabetes, sleep apnea, prolactin-sensitive conditions. The CD36-receptor cardiac activity adds theoretical considerations for people with active cardiac disease that haven't been characterized in human chronic-use contexts.

References

Imbimbo BP, Mant T, Edwards M, et al. (1994). "Growth hormone-releasing activity of hexarelin in humans. A dose-response study." Eur J Clin Pharmacol, 46(5), 421–425. PubMed
Arvat E, Maccario M, Di Vito L, et al. (2001). "Endocrine activities of ghrelin, a natural growth hormone secretagogue (GHS), in humans: comparison and interactions with hexarelin, a nonnatural peptidyl GHS, and GH-releasing hormone." J Clin Endocrinol Metab, 86(3), 1169–1174. PubMed
Rahim A, O'Neill PA, Shalet SM. (1998). "Growth hormone status during long-term hexarelin therapy." J Clin Endocrinol Metab, 83(5), 1644–1649. PubMed
Locatelli V, Rossoni G, Schweiger F, et al. (1999). "Growth hormone-independent cardioprotective effects of hexarelin in the rat." Endocrinology, 140(9), 4024–4031. PubMed
U.S. Food and Drug Administration. (2023). "Pharmacy Compounding Guidance. FDA Category 2 List." FDA.gov

For educational and research purposes only. This is not medical advice. Hexarelin is not FDA-approved and is on the FDA's Category 2 list as of September 2023. Consult a licensed healthcare provider before considering any peptide. PeptideLibraryHub is independent and does not sell peptides or accept money from anyone who does.