Hexarelin: the complete research guide.

Among growth-hormone-releasing peptides studied in the preclinical literature, hexarelin stands out as the most potent of the older GHRPs, with a broad preclinical story spanning cardioprotection, kidney protection, and anti-inflammatory effects — all attributed to a single six-amino-acid molecule. It also carries a well-documented limitation: receptor desensitization develops rapidly with repeated dosing. That tolerance phenomenon — tachyphylaxis — is the primary reason the research field has moved toward ipamorelin in modern protocols.

What is hexarelin?

Hexarelin is a synthetic peptide with six amino acids. The sequence is His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH₂. Three of those amino acids are D-stereoisomers, meaning mirror-image versions that resist normal enzyme breakdown. This structural feature contributes to greater metabolic stability relative to natural ghrelin.

Hexarelin belongs to the family called growth hormone-releasing peptides (GHRPs). It came in the second wave of this class, after GHRP-2 and GHRP-6. In head-to-head dose-response studies, hexarelin produced a higher peak GH response per unit dose than either older GHRP. That profile made it briefly attractive in the 1990s as a candidate for short-stature diagnostics and therapy.

The drug development never materialized. Hexarelin stalled at Phase II in every indication. Academic interest then shifted to effects that don't run through the growth hormone pathway at all. Specifically, hexarelin binds CD36, a scavenger receptor involved in cardiovascular biology, immune signaling, and lipid metabolism. That binding gives hexarelin a research story none of the other GHRPs have: a mechanism for heart protection that doesn't depend on GH. We'd argue that's what's driven most of the 2020–2026 literature.

One academic site dominates the field. We're talking about the University of Milano-Bicocca (the Meanti / Rizzi / Bresciani / Locatelli group). They've published consistently on hexarelin in neuroprotection, cardiology, and pulmonology since the 2010s, and they remain the most productive program on the molecule in 2026.

How it works.

The GH pathway: binding the ghrelin receptor.

Hexarelin's classical mechanism is binding the GHS-R1a receptor (the ghrelin receptor). GHS-R1a is expressed on somatotrophs, the GH-producing cells in the anterior pituitary. Binding triggers a calcium-based signaling cascade that stimulates GH release in a pulse.

The D-amino acid substitutions in the sequence confer metabolic stability. Natural ghrelin is degraded by enzymes within minutes; hexarelin's modifications extend circulating half-life sufficiently to evoke a measurable GH spike in pharmacological studies. The GH response has been reproduced across multiple published protocols.

The cardiovascular side door: CD36 binding.

Here's the part that makes hexarelin scientifically interesting. It also binds CD36, a scavenger receptor on immune cells, platelets, small blood vessels, and heart muscle cells. CD36 has multiple jobs: fatty-acid uptake, clearing oxidized LDL, thrombospondin-1 signaling, immune recognition.

GHRP-6 also binds CD36. Ipamorelin doesn't. The CD36 pathway is what gives hexarelin its cardiovascular effects independent of GH release. Take CD36 binding away, and the cardioprotection story mostly disappears. That fits with the fact that ipamorelin (the cleaner GHRP) has no cardioprotective preclinical literature.

Survival signaling.

A 2021 study in mouse nerve-cell cultures found hexarelin blocked cell death caused by hydrogen peroxide. The mechanism shifted cells toward survival (Meanti et al., 2021). The 2023 kidney-injury work shows the same pattern: hexarelin lowered death-signaling proteins and raised survival-signaling proteins (Guan et al., 2023).

Anti-inflammation.

A 2021 mouse aortic aneurysm study showed hexarelin suppressed inflammatory signaling and shut down the NLRP3 inflammasome, a cellular alarm complex. Aortic wall integrity held (Jiang et al., 2021). This NLRP3 effect connects hexarelin's cardiovascular, kidney, and lung findings. The same alarm complex shows up in atherosclerosis, kidney injury, and lung injury. Suppressing it in any of those tissues fits the broader pattern we're seeing.

Autonomic balance.

A 2020 mouse heart-attack study showed hexarelin shifted autonomic balance toward the parasympathetic (rest-and-digest) side. It also dropped inflammation markers and reduced interstitial collagen (McDonald et al., 2020). The parasympathetic shift lines up with older clinical pharmacology reports on heart-rate variability. It's a candidate mechanism for cardioprotection that doesn't depend on CD36 at all.

Preclinical dosing summary.

The following dose ranges are drawn from published preclinical literature to provide context for interpreting the cited studies. No human therapeutic dosing has been established or approved. Hexarelin is a research-use-only reference compound.

• Rodent injury models (subcutaneous): Published protocols report 0.1–0.3 mg/kg/day over 7–21 days. The 2020 McDonald cardiac study used 0.3 mg/kg/day for 21 days; the 2023 Guan kidney study used 0.1 mg/kg/day for 7 days prior to injury induction.
• Acute lung injury model (intraperitoneal): The 2021 Zambelli ARDS study administered 320 µg/kg as a single intraperitoneal dose pre- or post-injury.
• Historical pharmacology studies: Early-phase human pharmacology work examined single-bolus GH-stimulation protocols. The GH response was documented as non-linear, and tachyphylaxis was observed with repeated administration over days to weeks.

Administration routes studied.

Subcutaneous (preclinical standard route).

Subcutaneous delivery is the predominant route used across the published preclinical literature. Pharmacokinetic studies document that serum GH rises within 15–30 minutes of administration, with peak concentrations measured at 30–60 minutes in these models.

Intraperitoneal (rodent models).

Several rodent studies used intraperitoneal delivery, including the 2021 Zambelli ARDS study. This route is specific to the rodent model context and is not translatable to human research applications.

Oral route: bioavailability studies.

Hexarelin exhibits very low oral bioavailability. Multiple 2020–2023 studies investigated permeation enhancers to improve intestinal absorption. None produced a viable oral formulation (Dahlgren et al., 2021). Sublingual and nasal routes have also been explored in the literature with limited success.

Observed pharmacodynamic timeline (preclinical models).

• Minutes 15–60: Published pharmacokinetic studies report measurable serum GH elevation following a single dose, with peak concentrations at 30–60 min.
• Hours 2–6: GH returns toward baseline in preclinical pharmacology data. Any cortisol and prolactin elevations follow a similar time course.
• Days 1–7 (in vivo injury models): Protective biomarker changes — including reductions in TGF-β1 and NLRP3 activation and elevated Bcl-2/Bax ratios — were reported within the first dosing week in published rodent studies.
• Weeks 1–3 (in vivo models): Structural endpoints (preserved cardiac function, attenuated aneurysm progression, preserved kidney function) became measurable over this window in the cited studies. Tachyphylaxis also emerges in this window in GH-response pharmacology data, with documented attenuation of the GH signal under repeated dosing.
• Beyond 3 weeks: Receptor desensitization is well-documented as the primary pharmacological ceiling for sustained hexarelin administration in the published literature.

Research evidence.

Hexarelin's 2020–2026 preclinical literature is unusually diverse for a compound with no clinical translation. The 7 indications below are ordered by mechanistic strength, from the strongest preclinical signal to the weakest.

• Cardioprotection (myocardial ischemia-reperfusion model): A 2020 mouse study reported improved left-ventricular function, reduced collagen deposition, decreased TGF-β1 expression, and less myofibroblast differentiation following hexarelin treatment (McDonald et al., 2020).
• Abdominal aortic aneurysm (elastase model): A 2021 mouse study reported smaller aortic diameter, improved elastin integrity, preservation of smooth muscle cell contractile phenotype, and NLRP3 suppression (Jiang et al., 2021).
• Acute kidney injury (ischemia-reperfusion): A 2023 rat study found that pre-treatment preserved kidney function, reduced apoptotic cell death, and downregulated the MDM2/p53 pathway (Guan et al., 2023).
• ALS / neurodegeneration: A 2023 cell-line study using SOD1-G93A SH-SY5Y cells (an ALS model) reported reduced hydrogen peroxide cytotoxicity mediated through apoptosis-regulatory and survival pathways (Meanti et al., 2023).
• Acute lung injury / ARDS: A 2021 mouse model study reported improved lung compliance, reduced neutrophil recruitment, and less pulmonary collagen at 14 days (Zambelli et al., 2021).
• Obesity / metabolic phenotype: A 2021 MC4R-KO mouse study reported increased pulsatile GH, elevated lipolysis, lower hepatic lipid production, reduced visceral adiposity, and improved insulin sensitivity (Huang et al., 2021).
• Morphine tolerance (rodent model): A 2020 rat study reported that hexarelin co-administered with morphine attenuated analgesic tolerance in the study model (Baser et al., 2020).

The translational gap is notable. As of the 2020–2026 window, zero published Phase II or Phase III randomized controlled trials in humans exist for any indication. Older pre-2020 cardiovascular studies examined hexarelin's acute GH and blood-pressure effects in small human cohorts. None produced a clinical outcome signal strong enough to advance into pivotal trials. 35+ preclinical papers, zero human RCTs. The breadth of the preclinical literature stands in notable contrast to the absence of human trial data.

Hexarelin (roadmap)

Hexapeptide 6 aa GHS-R1a / CD36

Peptriva does not currently stock hexarelin. The catalog focuses on the GH-axis peptides with the cleanest pharmacodynamic profile and the strongest research signal — CJC-1295 (no DAC) on the GHRH-receptor side, and ipamorelin as the selective GHS-R1a agonist without the cortisol, prolactin, or tolerance buildup profile that limits hexarelin. See the catalog for the stocked GH-axis options.

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Co-administration literature.

Hexarelin appears infrequently as part of multi-compound protocols in the modern research literature, having largely been displaced by ipamorelin in repeat-dosing study designs. The combinations described below are drawn from pharmacology literature, not from controlled trial data.

• Hexarelin + GHRH analog (CJC-1295 or sermorelin): The literature rationale for this combination involves synergistic GH release through simultaneous stimulation of both the GHRH receptor and the GHS-R1a receptor on the somatotropic axis. Studies have examined whether peak GH responses exceed those of either compound alone. The contemporary literature has investigated the analogous CJC-1295 + ipamorelin combination, which offers a similar mechanistic rationale without the cortisol, prolactin, or tachyphylaxis profile associated with hexarelin.
• Hexarelin monotherapy cycling protocols: The pharmacology literature has noted that receptor desensitization under sustained dosing limits the utility of continuous hexarelin administration. Interrupted dosing schedules have been discussed in the research context; however, no controlled study has validated a specific cycling protocol for hexarelin.

For sustained GH-axis stimulation research, the published literature supports the CJC-1295 + ipamorelin combination as the current field-standard approach. CJC-1295 (no DAC) activates the GHRH receptor; ipamorelin selectively activates GHS-R1a without the cortisol, prolactin, or rapid desensitization documented for hexarelin.

Reconstitution, storage, and prep.

The following workflow represents the standard laboratory procedure used across the GH-axis lyophilized peptide category. The steps assume handling of research-grade material under appropriate laboratory conditions.

1. Let the lyophilized vial reach room temperature (about 10–15 minutes out of cold storage).
2. Draw 1–2 mL of bacteriostatic water into a 3 mL syringe with a 21g needle.
3. Inject the bacteriostatic water along the inner wall of the vial. Don't aim the stream directly at the powder, which can denature the peptide.
4. Swirl gently (don't shake) until the powder fully dissolves into a clear solution.
5. Label the vial with reconstitution date, concentration (mg per mL), and the lot number from the CoA.
6. Storage temperature for the reconstituted vial: 2–8°C (refrigerator), tightly sealed, protected from light.
7. Use within 4–6 weeks of reconstitution. The lyophilized starting material has a typical shelf-life of 24 months at –20°C when sealed.
8. Avoid repeated freeze-thaw cycles of the reconstituted solution. Potency loss is faster than for unmodified shorter peptides.

Side effects.

Commonly reported in the pharmacology literature.

• Transient cortisol elevation at GH-stimulating doses. Published comparisons report lower cortisol elevation than GHRP-6 and higher than ipamorelin.
• Transient prolactin elevation, with a similar comparative dose-response profile.
• Injection-site reactions (redness, brief discomfort) in subcutaneous administration studies.
• Mild flushing or warmth, particularly at higher dose levels examined in pharmacology studies.

Less commonly reported.

• Headache.
• Mild appetite increase. Less pronounced than GHRP-6, which demonstrates the strongest appetite-driving effect in the class via the ghrelin pathway.
• Transient changes in heart-rate variability, consistent with the autonomic-rebalancing effects documented in animal models.

Rare, serious, or theoretical.

• Long-term cardiac effects with chronic dosing. Older clinical-pharmacology literature reported positive inotropic effects that raised long-term safety questions. No long-term human safety dataset exists to resolve this.
• Receptor downregulation / tolerance buildup. The GH response attenuates with repeat dosing. This is the dominant pharmacological limit documented in the literature.
• Unknown effects on the broader CD36 axis. CD36 has documented roles in lipid uptake, immune signaling, and platelet function. Sustained agonism of this scavenger receptor lacks a long-term human safety dataset.

Legal status.

Hexarelin is available in the US as a research reference compound. It is not FDA-approved for any indication. It is not EMA-approved either. No completed Phase III trial exists. No active pivotal trial was enrolling as of May 2026. It is sold legally labeled for laboratory use only. Selling or marketing it as a therapeutic, or with human administration instructions, falls within FDA jurisdiction and draws enforcement against the supplier.

The DEA doesn't schedule hexarelin. It's not a controlled substance.

Sports and WADA.

Hexarelin is on the WADA 2026 Prohibited List under section S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics). It's classified as a growth hormone secretagogue / releasing peptide. The S2 category explicitly names GH-releasing peptides, and hexarelin sits there alongside GHRP-2, GHRP-6, ipamorelin, ibutamoren (MK-677), and tabimorelin.

Prohibition window: in-competition and out-of-competition for all athletes governed by WADA-compliant sports bodies.

Detection: reliable in athlete urine using modern LC-MS/MS assays. Detection windows for the parent peptide are short (hours). But metabolite tracking and the indirect biological-passport approach (longitudinal IGF-1 and bone-marker monitoring) extend the practical window.

Hexarelin vs. the rest of the GHRP class.

The published literature frequently positions hexarelin relative to the broader GHRP class. The comparative profiles below are summarized from pharmacology studies and published head-to-head data.

• vs. GHRP-2: Hexarelin has higher GH-release potency. Both elevate cortisol and prolactin transiently. Hexarelin's elevations are reported as similar or slightly lower than GHRP-2 at equipotent GH doses. GHRP-2 has a Japan diagnostic-use approval (KP-102, short-stature testing). Hexarelin has no comparable regulatory pathway.
• vs. GHRP-6: Hexarelin has higher GH potency and lower appetite-driving effect. GHRP-6 is the strongest ghrelin-pathway appetite stimulator in the class. GHRP-6 also elevates cortisol and prolactin more than hexarelin.
• vs. ipamorelin: Ipamorelin is the selective option in the class. Studies report similar GH-release potency to GHRP-2 with minimal cortisol, prolactin, or appetite effects and no notable tolerance buildup at research-protocol doses. This selectivity profile is the basis for ipamorelin becoming the field-standard pairing for CJC-1295 in modern research.
• vs. tesamorelin (the only FDA-approved GH-axis peptide): Tesamorelin is a GHRH analog (different receptor, different mechanism), FDA-approved for HIV-associated lipodystrophy. Two pivotal Phase III RCTs (n=410, n=404) support the approval. Hexarelin has zero comparable evidence in any indication.

CJC-1295 + Ipamorelin (in stock)

5 mg ≥99% pure Lyophilized

The modern GH-axis combination studied in the published literature is CJC-1295 (no DAC) + ipamorelin — GHRH-receptor activation paired with selective GHS-R1a agonism, without the cortisol, prolactin, or rapid desensitization characteristics documented for hexarelin. Research-grade reference compound; COA available per lot.

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Frequently asked questions

What is hexarelin?

Hexarelin is a synthetic six-amino-acid peptide developed in the 1990s as a growth hormone secretagogue. It binds GHS-R1a (the ghrelin receptor) on the anterior pituitary to stimulate GH release. It also binds CD36, a scavenger receptor, which is the mechanistic basis of its cardioprotective preclinical signal. It's not FDA-approved. No completed Phase III trial. WADA-prohibited (S2). The University of Milano-Bicocca runs the most consistent academic program studying it.

Hexarelin vs. GHRP-2 vs. GHRP-6 vs. ipamorelin: how do they compare in the research literature?

All four are growth hormone secretagogues acting on GHS-R1a. Their off-target profiles diverge meaningfully. Hexarelin has the highest GH-release potency but also elevates cortisol and prolactin (less than GHRP-6, more than ipamorelin). Tachyphylaxis has been documented with repeat dosing. Hexarelin uniquely binds CD36, which is the mechanistic basis for its cardioprotection literature. GHRP-2 also elevates cortisol/prolactin. GHRP-6 additionally drives strong appetite via the ghrelin pathway. Ipamorelin has emerged as the field-standard choice in contemporary research. Published studies report similar GH release to GHRP-2 with minimal cortisol, prolactin, or appetite effects and no notable tolerance buildup — which is why it became the standard GHS-R1a pairing for CJC-1295.

Is hexarelin FDA-approved?

No. Hexarelin is not approved by the FDA, EMA, or any major regulatory body for any indication. There is no completed Phase III trial. It is sold legally in the US as a research reference compound labeled for laboratory use only and cannot be marketed or used as a therapeutic. Tesamorelin is the only FDA-approved peptide in the broader GH-axis category, and that approval is specifically for HIV-associated lipodystrophy.

Why does hexarelin tolerance build so fast?

Chronic stimulation of the GHS-R1a receptor leads to receptor desensitization and downregulation — the same phenomenon that affects most G-protein-coupled receptors under sustained agonism. Hexarelin's high potency is documented as accelerating this process relative to more selective agonists such as ipamorelin. Published pharmacology studies report that the GH response attenuates with daily dosing over days to weeks, which is the primary pharmacological reason hexarelin was displaced by ipamorelin in repeat-dosing research protocols. Interrupted dosing schedules have been discussed in the research literature to address tachyphylaxis; however, no controlled trial has validated a specific approach for hexarelin.

Hexarelin cardiac effects: are they real?

The cardioprotection signal in acute ischemic-injury models is real but narrow. A 2020 mouse heart-attack study (McDonald et al.) showed hexarelin improved LV function, reduced collagen, and decreased TGF-β1 expression. The mechanism involves CD36 binding, NF-κB / NLRP3 inflammasome suppression, and autonomic rebalancing toward parasympathetic tone. A 2021 abdominal aortic aneurysm mouse study and a 2023 rat kidney injury study showed similar tissue-protective signals.

The negative side: a 2022 synchrotron-imaging study in a chronic pulmonary hypertension rat model found hexarelin did not prevent right-ventricular hypertrophy or cardiomyocyte relaxation impairment (Waddingham et al., 2022). Cardioprotection is condition-specific, not universal. And no human RCT has tested it.

What is hexarelin's WADA status?

Hexarelin is on the WADA 2026 Prohibited List under section S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics) as a growth hormone secretagogue / releasing peptide. It's prohibited in-competition and out-of-competition for all athletes governed by WADA-compliant sports bodies. Detection in athlete urine is reliable with modern LC-MS/MS assays.

How much does research-grade hexarelin cost?

As a six-amino-acid peptide without lipid modifications, hexarelin sits at the low end of synthesis complexity relative to longer GH-axis peptides such as tesamorelin (44 aa) or retatrutide (39 aa). Market pricing for research-grade material has typically ranged from $45–$80 for 5 mg vials and $75–$140 for 10 mg vials, depending on supplier and purity tier. Pricing significantly below this range warrants identity verification, as even simple peptides carry a real synthesis-cost floor and credible suppliers absorb the cost of third-party CoA testing. Peptriva does not stock hexarelin; the catalog focuses on GH-axis peptides with stronger research signal: CJC-1295, ipamorelin, and tesamorelin.