Hexarelin Acetate Peptide Guide: The Most Potent GHRP for GH Release and Cardiac Research

✓ Medically reviewed by  ·  Last reviewed: May 2026

Morgan Ellis

Pharmacy Researcher · 8 years experience

Pharmacy researcher with 8 years reviewing clinical drug information, generic formulation equivalence, and international pharmaceutical standards. Focuses on patient-facing accuracy in medication education.

What is hexarelin and how does it work?

Hexarelin — also published under the names Examorelin and the laboratory code EX-7 — is a synthetic hexapeptide developed by Mediolanum Farmaceutici in the early 1990s as a next-generation analogue of GHRP-6. Its sequence is His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH₂, and it is identified in the chemical literature by CAS 140703-51-1 (acetate salt: CAS 140703-52-2).

The single methylation at position two — the 2-methyl-tryptophan substitution — is what distinguishes hexarelin from its parent GHRP-6 peptide. That single change dramatically improves resistance to enzymatic degradation, extends the in-vivo half-life, and roughly doubles potency on a microgram-for-microgram basis (Imbimbo BP et al., European Journal of Endocrinology 1994, PMID 7957536).

Mechanistically, hexarelin is a growth hormone secretagogue (GHS). It binds the ghrelin receptor (GHSR-1a) on somatotrophs in the anterior pituitary, triggering a phospholipase-C–IP₃–calcium cascade that releases stored growth hormone. Because the mechanism is calcium-pulse driven rather than transcription-driven, the GH spike appears within 15–30 minutes of administration, peaks in the first hour, and returns toward baseline within 2–3 hours.

Hexarelin shares this ghrelin-mimetic pulse mechanism with the closely related compounds GHRP-2 and GHRP-6 (compared here), with Ipamorelin (covered in the CJC-1295 stack guide), and with the newer orally active compound MK-677 (Ibutamoren). It is pharmacologically distinct from the GHRH analogue family — Sermorelin, CJC-1295 and Tesamorelin — which act on a different pituitary receptor (GHRH-R) and produce a slower, sustained GH-axis modulation rather than a pulse (see our Tesamorelin vs Sermorelin comparison).

If you are new to the GH-peptide landscape and want the wider map first, the Best Growth Hormone Peptides hub compares all 10 commonly researched GH and GH-axis peptides side by side, including recombinant 191AA somatropin and the lipolysis-selective fragment HGH Fragment 176–191.

Receptor biology — GHSR-1a, CD36 and why both matter

Hexarelin is unusual in the GHRP family because it binds two distinct receptors with biologically meaningful affinity. Understanding both is essential before reading any of the cardiac literature.

1. GHSR-1a — the canonical ghrelin receptor

The primary receptor mediating hexarelin’s GH-releasing effect is the growth hormone secretagogue receptor type 1a (GHSR-1a, also called the ghrelin receptor). This is a G-protein-coupled receptor expressed densely on pituitary somatotrophs and hypothalamic arcuate-nucleus neurons. Hexarelin binds GHSR-1a as a full agonist with an affinity comparable to native ghrelin but with substantially better metabolic stability — native ghrelin is degraded within minutes by deacylating enzymes, while hexarelin survives in plasma long enough to produce a measurable, reproducible GH pulse.

For the broader pharmacology of GH-axis regulation and where ghrelin/GHRP signals sit relative to GHRH and somatostatin, the freely available Endotext chapter on Growth Hormone Physiology (NCBI Bookshelf NBK279081) is the standard endocrinology reference.

2. CD36 — the cardiovascular surprise

The second receptor — and the reason hexarelin keeps reappearing in cardiology rather than pure endocrinology research — is CD36. CD36 is a scavenger-receptor family glycoprotein expressed on cardiomyocytes, macrophages, microvascular endothelium and adipocytes. It is not a classical GH-axis receptor at all; its better-known roles are in fatty-acid uptake, oxidised-LDL recognition and thrombospondin signalling.

Bodart and colleagues (Bodart V et al., Circulation Research 2002, PMID 11322493) demonstrated that hexarelin binds CD36 directly on cardiomyocyte membranes, and that this binding mediates cardioprotective effects in ischaemia–reperfusion models independently of GH release — confirmed because the protection persisted in hypophysectomised animals where no GH response was possible.

The clinical-research significance: hexarelin is the only first-generation GHRP with documented dual-receptor binding at physiologically meaningful concentrations. Ipamorelin, GHRP-2 and GHRP-6 are selective for GHSR-1a. Newer-generation compounds were specifically engineered to eliminate CD36 affinity — for reasons we will return to in the cortisol/prolactin section.

The Imbimbo dose-response curve and what it actually means

The single most cited paper in the hexarelin literature is the 1994 dose-response study by Imbimbo and colleagues. It established the doses that subsequent research has used for the last three decades.

Three observations from this curve dominate downstream research:

1. The pituitary saturates at roughly 1–2 mcg/kg IV. Higher doses do not produce a meaningfully larger GH pulse — they only increase the side-effect load. This is the pharmacological basis for the “1 mcg/kg standard research dose” that appears in every subsequent paper.
2. Subcutaneous bioavailability is roughly 60–70% of IV. Most chronic research has therefore used 2 mcg/kg SC as the equivalent of 1 mcg/kg IV.
3. Intranasal bioavailability is roughly 15–20% of IV. Intranasal hexarelin was developed for paediatric short-stature research where avoiding daily injections mattered; reported nasal doses of 20 mcg/kg approximate 3–4 mcg/kg IV.

For comparison with related secretagogues at standardised doses, see the GHRP-2 vs GHRP-6 head-to-head — hexarelin produces a roughly 1.5× larger peak GH response than GHRP-2 and roughly 2× larger than GHRP-6 at the standard 1 mcg/kg IV dose, but with proportionally greater cortisol/prolactin co-release.

Hexarelin vs Ipamorelin, GHRP-2 and GHRP-6

The four classical GHRPs are often grouped together, but they occupy quite different positions on the potency–selectivity axis. The table below summarises the published research consensus.

The trade-off is the central pharmacological story: hexarelin is the most potent on the GH axis, but the least selective overall. Ipamorelin, the most recently developed of the four, was engineered specifically to retain the GH-releasing potency of the GHRP family while losing the cortisol/prolactin co-stimulation that GHRP-2 and especially hexarelin display at higher doses. The 2017 secretagogue safety review by Sigalos & Pastuszak (PMID 28400207) covers this trade-off explicitly.

For most modern GH-axis research the field has migrated away from hexarelin toward Ipamorelin or to the GHRH-analogue family. Hexarelin retains a research-niche role for two specific reasons: the maximal GH response is highest, and the CD36 activity is unique and continues to generate cardiac-research interest.

Cardiac research findings — the most distinctive feature

The cardiac literature on hexarelin is sizeable and growing. Three lines of evidence are the most established.

Cardioprotection in ischaemia–reperfusion models

Multiple animal-model studies have shown that hexarelin pre-treatment reduces infarct size after coronary-artery occlusion and reperfusion. The protection persists in hypophysectomised animals, demonstrating that it is independent of pituitary GH release and downstream IGF-1. The mediator is direct CD36 binding on cardiomyocytes with downstream activation of cell-survival pathways including PI3K-Akt and inhibition of mitochondrial permeability-transition pore opening. The mechanistic literature is summarised in the comprehensive review by Mao, Tokudome and Kishimoto (PMID 25278975).

Inotropy and left-ventricular function

Acute hexarelin administration in animal heart-failure models increases left-ventricular contractility and ejection fraction. Importantly this effect is observed at sub-GH-releasing doses — consistent with a direct cardiac action rather than a downstream IGF-1 effect. Bisi and colleagues reported the seminal human cardiac haemodynamic data in 1999 in a small healthy-volunteer study showing increased left-ventricular ejection fraction within 30 minutes of IV hexarelin.

Vascular and atherosclerosis-modifying effects

CD36 is also expressed on macrophages and microvascular endothelium. Several studies have shown that hexarelin reduces foam-cell formation and modulates macrophage cholesterol handling in atherosclerosis-model animals. This is genuinely novel pharmacology for a peptide originally developed as a GH secretagogue, and it is the line of research where hexarelin shows the most distinctive separation from its GHRP siblings.

Routes and bioavailability — IV, SC, intranasal, oral

Hexarelin has been studied across four administration routes. Each route has a defined research niche.

• Intravenous (IV) bolus — the reference route. Gives the cleanest pharmacokinetic profile and is the route used for almost all dose-response and provocative-test research. Onset within 15 minutes; GH peak at 30–45 minutes; return to baseline by 2–3 hours.
• Subcutaneous (SC) injection — bioavailability roughly 60–70% of IV. The route most commonly used in chronic-dosing research because it does not require repeated venous access. Onset delayed by 20–30 minutes relative to IV.
• Intranasal — bioavailability roughly 15–20% of IV. Developed specifically for paediatric short-stature research where avoiding repeated injections in children was a priority. Pulmonary absorption can complicate the pharmacokinetic profile if administration technique is inconsistent.
• Oral — bioavailability under 1%. Generally not pharmacologically useful and not pursued in research.

For the broader framework on selecting and comparing peptide administration routes — bioavailability, onset, sterile-handling implications and which routes pair sensibly with which compounds — see our Peptide Injection Routes guide (SC, IM, intranasal).

Receptor desensitization and the chronic-dosing ceiling

The single most important practical limit on chronic hexarelin research is receptor desensitization. Continuous or near-continuous GHSR-1a agonism leads to receptor internalisation and downregulation, and within 7–14 days of daily dosing the GH-pulse response measurably attenuates. By 4 weeks of continuous dosing the GH response can fall to 30–50% of the day-1 response.

This is not unique to hexarelin — every GHSR-1a agonist studied (GHRP-2, GHRP-6, Ipamorelin, MK-677) shows the same pattern — but it is more pronounced with hexarelin because the receptor occupancy at standard doses is higher. Three patterns have been used in research literature to mitigate desensitization:

1. Pulsatile dosing (the most common research pattern) — once-daily or twice-daily injection with a wash-out period each week.
2. Cycled dosing — 4–8 weeks on, 4 weeks off — discussed in detail in our Peptide Cycling Protocols guide.
3. Co-administration with a GHRH analogue — hexarelin paired with a Sermorelin- or CJC-1295-class compound stimulates the GH axis via two independent receptors and partially blunts the desensitization that develops with GHSR-1a-only dosing.

Co-administration research with CJC-1295/Ipamorelin combinations is now the dominant chronic-dosing paradigm in the GHRP literature. The mechanistic logic is set out in our Ipamorelin + CJC-1295 stack guide.

Cortisol, prolactin and the supraphysiological-dose problem

At doses up to the pituitary-saturation point of roughly 1–2 mcg/kg IV, hexarelin produces a clean GH pulse with minimal disturbance of other anterior-pituitary hormones. Above this point — and particularly at the 4 mcg/kg and higher doses sometimes used in older provocative-test research — a measurable rise in ACTH/cortisol and prolactin appears.

The mechanism is not fully resolved. It may reflect spillover binding at related receptors at high concentrations, or it may reflect CD36-mediated effects on pituitary corticotrophs and lactotrophs. The Sigalos & Pastuszak review (PMID 28400207) treats this as the principal pharmacological argument for using the newer-generation, GHSR-1a-selective compounds (Ipamorelin, MK-677) when the research question is GH-axis biology rather than cardiac CD36 biology.

Reconstitution, storage and laboratory handling

Hexarelin is supplied as a sterile lyophilised acetate powder. Standard laboratory reconstitution practice:

• Diluent: bacteriostatic water (0.9% benzyl alcohol) for multi-use reconstitution, or sterile water for injection for single-use studies.
• Concentration: typically 1 mg/mL or 2 mg/mL — concentrations above 5 mg/mL increase aggregation risk in storage.
• pH: reconstituted solution pH 4–6; outside this range degradation accelerates.
• Storage of lyophilised powder: −20°C protected from light; stable 24+ months unopened.
• Storage of reconstituted solution: 2–8°C; use within 14 days for bacteriostatic-water reconstitution, within 7 days for sterile-water reconstitution.
• Avoid: repeated freeze–thaw cycles of reconstituted material; vortexing (use gentle inversion); contact with metal cation surfaces (degrades the methylated tryptophan).

Our full laboratory-handling protocol is set out in the Peptide Storage & Cold-Chain guide, and reconstitution-volume mathematics is covered in How to Reconstitute Peptides.

Research-grade sourcing — what to look for on a COA

Because hexarelin is sold as a laboratory reagent (not a medicine), the quality bar is set by analytical-chemistry documentation rather than pharmacopoeia compliance. A defensible research-grade Certificate of Analysis (COA) for hexarelin will document at minimum:

1. Identity — mass spectrometry confirmation of the molecular ion (theoretical monoisotopic mass for hexarelin free base: 887.0 Da; observed [M+H]⁺ ~888 Da).
2. Purity — RP-HPLC purity ≥99% at 220 nm absorbance, with the chromatogram included in the COA. Single significant impurity peak <0.5%.
3. Counter-ion — acetate content (typically 7–12% by mass for the acetate salt).
4. Water content — Karl Fischer titration <8%.
5. Endotoxin — LAL test <1 EU/mg for products intended for in-vivo research use.
6. Bacterial bioburden — <100 CFU/g.
7. CAS number — 140703-51-1 (free base) or 140703-52-2 (acetate salt). Anything else is mislabelled.

The standard methodology for reading and verifying a peptide COA is set out in our dedicated How to Read a Peptide COA guide.

MedsBase supplies Hexarelin Acetate (Examorelin) as a research-grade laboratory reagent from a WHO-GMP-certified manufacturer, with HPLC purity ≥99%, full batch COA on file, and CAS-keyed labelling. Worldwide Shipping. The compound is supplied for laboratory and research use only.

Frequently Asked Questions

Is hexarelin the same compound as Examorelin or EX-7?

Yes. All three names refer to the same hexapeptide, CAS 140703-51-1. “Hexarelin” is the most common name in the modern research literature. “Examorelin” was the original development name used by Mediolanum Farmaceutici in the early 1990s and appears in older European clinical-research papers. “EX-7” is the laboratory code from the same development programme.

How does hexarelin compare to Ipamorelin for GH release?

At equivalent molar doses, hexarelin produces a roughly 50% larger peak GH pulse than Ipamorelin. The trade-off is selectivity: Ipamorelin produces essentially no cortisol or prolactin co-release, while hexarelin produces measurable cortisol/prolactin elevation at supraphysiological doses. For GH-axis-focused research, the modern preference is Ipamorelin (often combined with a GHRH analogue such as CJC-1295). For CD36-mediated cardiac research, only hexarelin works.

Is hexarelin orally bioavailable?

No, not meaningfully — oral bioavailability is under 1% because the peptide is degraded by gastric and pancreatic proteases. The orally active growth-hormone secretagogue in the same pharmacological class is MK-677 (Ibutamoren), a non-peptide ghrelin-receptor agonist. Hexarelin itself is studied by IV, SC, or intranasal administration.

What does CD36 binding actually do?

CD36 is a scavenger receptor present on cardiomyocytes, macrophages, microvascular endothelial cells, and adipocytes. When hexarelin binds CD36 on cardiomyocytes it activates intracellular survival pathways (notably PI3K-Akt and ERK1/2) that reduce apoptosis after ischaemia–reperfusion injury. This action is independent of GH release and has been demonstrated even in hypophysectomised animals. On macrophages, CD36 binding by hexarelin appears to reduce foam-cell formation in atherosclerosis-model animals. The full mechanism review is in PMID 25278975.

Why has hexarelin not been developed as a medicine?

Several reasons. The GH-axis indication was overtaken by recombinant human growth hormone (somatropin 191AA) and by the GHRH-analogue family which offer cleaner dosing profiles. The cardiac CD36 indication has remained interesting but technically challenging — designing a clinical trial for a cardioprotective agent given pre-emptively before an unpredictable ischaemic event is logistically difficult. As of 2026, hexarelin remains a research-only compound with no marketing approval in any jurisdiction. Generalised endocrinology and growth-axis background is maintained at NIDDK and MedlinePlus Growth Disorders.

Does hexarelin cause hunger like GHRP-6?

Less than GHRP-6. The appetite-stimulating effect of GHRP-6 is mediated by GHSR-1a in the hypothalamic arcuate nucleus and is dose-dependent. Hexarelin has comparable arcuate-nucleus receptor occupancy in principle, but most reported research describes the appetite effect as modest at standard doses and prominent only at higher doses. GHRP-2 sits between the two. Ipamorelin produces essentially no appetite effect at standard doses.

How long is a typical research cycle?

Published GH-axis research cycles range from 7 days (acute dose-response studies) to 16 weeks (chronic-administration GH-pulse studies). Because of receptor desensitization, continuous daily dosing beyond 4 weeks attenuates the GH response measurably. The dominant chronic-dosing paradigm in modern research is pulsatile or cycled — see our Peptide Cycling Protocols guide for the standard approaches. For acute provocative-test research, 1–3 doses at standard 1 mcg/kg IV is sufficient.

How does hexarelin interact with the lipolytic fragment HGH 176–191?

The compounds operate on different axes. Hexarelin acts upstream — releasing endogenous GH that then drives both lipolysis and tissue anabolism via IGF-1. HGH 176–191 acts downstream — it is a fragment of the GH molecule’s C-terminus that reproduces only the lipolytic activity of GH without the IGF-1 or anabolic effects (see our HGH Fragment 176-191 guide). Some research groups have combined them on the logic that fragment-driven fat-cell lipolysis can run in parallel with hexarelin-driven pulsatile GH release, but the published evidence base for the combination is small.

Is there a comprehensive PubMed reference for hexarelin?

The most efficient entry point is the full PubMed search for “hexarelin”, which returns roughly 600 peer-reviewed papers spanning 1994 to the present. For mechanistic depth start with the Bodart 2002 CD36-receptor paper (PMID 11322493), the Imbimbo 1994 dose-response paper (PMID 7957536), and the Mao 2014 cardiovascular review (PMID 25278975).

Outbound research references in this guide: PMID 7957536 — Imbimbo dose-response · PMID 11322493 — Bodart CD36 · PMID 25278975 — Mao cardiovascular review · PMID 28400207 — Sigalos secretagogue safety review · PubMed: all hexarelin papers · NCBI Bookshelf — GH physiology · NIDDK — Acromegaly · MedlinePlus — Growth disorders.

Written by

Sophie Chen

Pharmaceutical Content Researcher · 8 years experience

Sophie Chen is a pharmaceutical content researcher with 8 years covering generic medication access and clinical pharmacology. She specialises in international regulatory frameworks, bioequivalence standards, and patient-facing education on therapeutic drug classes. She is not a clinician.