Hexarelin: The Growth Hormone Secretagogue That Stops Working

Hexarelin has more human data behind it than any other growth hormone secretagogue on this site, and the data is unflattering. Sixteen weeks of twice-daily dosing cut the growth hormone response by 45%, and IGF-1, body composition and bone density did not move.

That single study is why hexarelin is worth taking seriously and why almost nothing written about it survives contact with the record. It sits in the growth hormone peptides category, it is sold as the strongest and the cardioprotective member of its class, and it is chemically GHRP-6 plus one methyl group. Each of those three statements has an evidence trail, and they do not all point the same way.

Does hexarelin stop working?

Yes, partially, and the decline was measured rather than inferred. In Rahim, O'Neill and Shalet's 1998 study in JCEM, adults given subcutaneous hexarelin 1.5 µg/kg twice daily for 16 weeks saw area-under-curve growth hormone fall from 19.1 µg/L·h at baseline to 10.5 µg/L·h at week 16, about a 45% reduction. The attenuation was partial and fully reversible: AUC-GH returned to baseline four weeks after stopping.

That is the only long-duration human dosing study of this compound, which makes it the ceiling of what anyone knows about hexarelin over months rather than hours. Everything else in the human literature is a single dose or a single day.

Two words in the finding matter more than the percentage. Partial means the response degraded rather than disappeared; subjects at week 16 were still releasing growth hormone, just less of it. Reversible means the pituitary was not damaged — four weeks away from the drug restored the original response completely. Whatever hexarelin does to the GHS-R1a signalling pathway over four months, it undoes.

What did 16 weeks of hexarelin actually change?

Nothing downstream. Across the same 16 weeks of twice-daily subcutaneous dosing that produced sustained growth hormone pulses, IGF-1 and IGFBP-3 did not change significantly, body composition did not change, and bone mineral density did not change. Of the bone markers measured, only C-terminal propeptide of type I collagen rose. Four months of GH release in humans produced no measurable anabolic outcome, which is the most underreported result in the hexarelin file.

This finding deserves more weight than the desensitisation number it is usually bundled with. The entire commercial argument for a growth hormone secretagogue is that GH pulses convert into IGF-1 and then into lean mass, fat loss and bone. In the one study that dosed humans long enough to look, the first conversion did not happen and neither did the second.

The rise in C-terminal propeptide of type I collagen is a bone formation marker, not an outcome. It moved; bone mineral density did not.

What is hexarelin, and why is it one methyl group away from GHRP-6?

Hexarelin is a synthetic hexapeptide, His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH₂, molecular weight 887.0 g/mol, CAS 140703-51-1, with the INN examorelin. It agonises GHS-R1a and also binds CD36. Structurally it is 2-methyl-GHRP-6: the two molecules differ by 14.0157 daltons, a single CH₂. Both are hexapeptides carrying two indole chromophores, with near-identical UV absorbance at 214 and 220 nm and closely similar chromatographic retention, which is why a routine purity certificate cannot tell the two apart.

There is a naming trap here. Regulatory documents list the compound as examorelin (hexarelin), so searching only for "hexarelin" will miss WADA and pharmacopoeia entries entirely. Two CAS numbers appear on the free-base record, likely a free-base-versus-salt distinction — treat either with a caveat rather than asserting one.

The GHRP-6 relationship is the single most practical fact about buying this compound, and it is rarely stated.

Against the rest of the class, hexarelin's position is distinctive on human data and unremarkable on selectivity.

The three-way comparison most buyers arrive with, GHRP-2 vs GHRP-6 vs ipamorelin, leaves hexarelin out — which is part of why its substitution risk goes unnoticed. Full identity details sit on the hexarelin compound page.

Does hexarelin raise cortisol in humans?

Yes, and unlike most questions in this class it was answered directly in people. Arvat et al. 1997, in Peptides, measured GH, prolactin, ACTH and cortisol after GHRP-2 and hexarelin in six young adults and six elderly subjects, against GHRH, TRH and hCRH comparators. Hexarelin produced GH responses exceeding GHRH at higher doses and a slight stimulatory effect on prolactin, ACTH and cortisol, with cortisol effects comparable to hCRH.

The human answer is therefore unambiguous: hexarelin is not selective. Any description of it as a "clean" growth hormone secretagogue contradicts the primary human literature, not a gap in it.

This is also where the class's evidence asymmetry becomes visible. For hexarelin, the selectivity question was put to humans and answered — it raises cortisol. For ipamorelin, the same question was only ever put to pigs. Comparing the two on "cleanliness" therefore compares a human measurement with an animal one.

Who responds to hexarelin, and who doesn't?

Hexarelin's growth hormone response is strongly conditional on age and on pituitary integrity. Bellone et al. 1998 tested four age cohorts at 2 µg/kg intravenously and found the response powerful in pubertal children and young adults but markedly reduced in prepubertal children and the elderly. Maghnie et al. 1998, comparing 18 GH-deficient patients with 24 short normal children, concluded that "the integrity of the hypothalamic pituitary connections is essential", with responses correlating to GHRH responses at r = 0.746, P<0.0001.

The two papers do not fully agree. Bellone found elderly responses markedly reduced; Arvat 1997 found elderly responses similar to young. Different doses and different designs explain some of it, and the inconsistency is worth stating rather than smoothing over.

What both establish is that hexarelin is not a uniform effect. It depends on where a person is in life and on an intact hypothalamic-pituitary axis, which is a stronger conditionality than anything documented for its class siblings.

Is hexarelin cardioprotective?

Hexarelin's cardiac mechanism is real in rodents, and its human effect vanished in the diseased hearts the claim targets. Bodart et al. 2002, in Circulation Research, identified the 84 kDa cardiac binding protein as CD36 and showed hexarelin's coronary vascular effect disappeared in CD36-null mice. In humans, Bisi et al. 1999 raised ejection fraction in seven male volunteers from 64.0 ± 1.5% to 70.7 ± 3.0%, p<0.03. Broglio et al. 2001 found no such effect in 12 dilated-cardiomyopathy patients.

Take the mechanism first, because it is genuinely novel. Bodart localised CD36 to cardiomyocytes and endothelial cells, and the coronary vascular response also disappeared in CD36-deficient hypertensive rats. That establishes CD36, not GHS-R1a, as the mediator of that particular action. It is rat and mouse work on a coronary vascular response, and it is not cardioprotection in humans.

The human ejection-fraction effect measured by Bisi was short-lasting: it appeared at 15 minutes, peaked at 30, and was gone by about 60. It was independent of GH, measured by radionuclide angiocardiography, and it came from seven volunteers.

Broglio then extended the design to three groups — 7 normal adults, 7 severely GH-deficient patients and 12 patients with severe dilated cardiomyopathy — and reported that hexarelin "significantly increased LVEF in normal and in GH-deficient subjects, but not in dilated cardiomyopathy." The effect was absent in exactly the population cardioprotection claims are aimed at. There is no human outcome trial, no chronic cardiac dosing study, and no mortality or morbidity data.

What hexarelin dose has been used in published human studies?

No validated protocol exists for non-clinical hexarelin use. Published human dosing runs from 1.5 µg/kg subcutaneously twice daily in the 16-week study to 2 µg/kg intravenously in the acute studies, all far below the milligram-scale conventions circulating in community protocols. The desensitisation finding carries a direct implication those protocols rarely acknowledge: the response degrades measurably over months of continuous use and recovers after about four weeks off.

Continuous year-round dosing is therefore unsupported by the one long-duration human study that exists. Build in time off if you are following the only human dosing schedule that has been published for longer than a day.

For the reconstitution arithmetic, use the peptide dosing calculator alongside the reconstitution calculator. Those tools convert a chosen dose into a syringe volume; nothing in the literature tells you which dose to choose.

Where does hexarelin sit with regulators?

Hexarelin is not approved for human use anywhere, and it appears on none of FDA's peptide lists: not the Category 2 significant-safety-risk list, not the 503A bulks list, and not the 503B nominated-substances document. That absence is not permission. Under 503A a bulk substance must be on the list, hold a USP monograph, or be a component of an approved drug, and hexarelin is none of those three.

It was also not on the 23–24 July 2026 PCAC agenda, which covered BPC-157, KPV, TB-500, MOTS-c, emideltide, Semax and Epitalon. Hexarelin was not reviewed and not rejected; it simply was never in the process. Our FDA peptide regulation timeline sets out which compounds moved and when.

In sport the position is explicit. WADA's 2026 Prohibited List carries it at S2.2.4 under GH-releasing peptides as "examorelin (hexarelin)" — prohibited at all times, non-specified. Anyone searching that list for "hexarelin" alone will not find it.

Which hexarelin claims survive the evidence?

One hexarelin claim is established, and most of the rest are refuted rather than merely unproven — an important distinction in this category. Powerful GH release in humans holds across multiple studies and routes. Selectivity is refuted in man, sustained anabolic benefit is refuted at 16 weeks, and freedom from tolerance is refuted by the 45% decline, though that decline reverses. Cardioprotection is overstated, consistency across users is conditional, and "strongest GHRP available" is an unsupported superlative.

Most peptides on this site are surrounded by absent evidence. Hexarelin is surrounded by present evidence that mostly says no, which is a different and more useful situation for a buyer.

How do you tell hexarelin from GHRP-6 in the vial?

Only mass spectrometry separates hexarelin from GHRP-6. The two differ by 14 daltons, which at m/z 887 is roughly 15,800 ppm and detectable on any instrument including a low-resolution single quadrupole. An HPLC-UV certificate reporting "99.0% purity" is entirely consistent with a vial of GHRP-6 mislabelled as hexarelin, because area percent measures homogeneity, not identity. The economics point the wrong way too: hexarelin's median price is $9.20/mg against GHRP-6's $3.90/mg.

The gap is procedural, not technical. Labs have to be asked to run mass spectrometry rather than HPLC alone, and most certificates in this market show HPLC alone.

One further certificate trap: acetate salt forms add roughly 60 Da per acetate to the weighed material without changing the peptide ion, a routine source of confusion explained in peptide salt forms.

The coverage asymmetry on this platform is itself part of the story, and it runs against us. The Purity Index records hexarelin at 99.03 across just 25 tests from 8 laboratories (verified August 2026), against a composite of 99.50 across 10,110 tests. The hexarelin compound page shows the same 25 tests averaging 99.02% (verified August 2026). Twenty-five tests is a thin denominator, and it sits on the compound in this class with the highest identity-confusion risk. By comparison, ipamorelin has 323 index-qualifying tests across 21 labs.

Hexarelin price data shows 9 shops in stock, a median of $9.20/mg and a low of $4.90/mg on a 10 mg vial (verified August 2026), spanning $4.90 to $18.33/mg. Those figures exclude shipping, taxes and customs, coupon codes, bulk tiers, multi-vial kits and account-gated pricing.

Method reading: mass spectrometry for peptides, how to read peptide lab test results and how to verify peptide quality before you buy.

The trial that would settle this

The trial that would settle hexarelin runs longer than 16 weeks, with washout arms, and measures body composition and function rather than growth hormone curves. It doses chronically in patients with actual cardiac dysfunction, since the one human study in that group found no ejection-fraction effect. It runs GHRP-6 head-to-head, since nobody has clinically compared two molecules separated by a single methyl group. And it uses mass-spectrometry-verified material throughout.

Frequently Asked Questions

Does hexarelin stop working?

Partly. Sixteen weeks of twice-daily subcutaneous dosing at 1.5 µg/kg reduced the area-under-curve growth hormone response by about 45%, from 19.1 to 10.5 µg/L·h. The effect was reversible — the response returned to baseline four weeks after stopping.

Is hexarelin cardioprotective?

The CD36 receptor mechanism is real, but it was demonstrated in rats and mice. In humans, a single intravenous dose raised ejection fraction for about an hour in healthy and GH-deficient subjects, and produced no effect at all in patients with dilated cardiomyopathy. There is no human outcome data.

Does hexarelin raise cortisol?

Yes. It was measured directly in humans alongside GHRP-2, with cortisol effects comparable to hCRH, and prolactin and ACTH also rose slightly. Hexarelin is not a selective growth hormone secretagogue, and the human literature says so directly rather than being silent on it.

Can hexarelin be confused with GHRP-6?

Easily, by HPLC. They differ by a single methyl group — 14 Da — and have near-identical UV absorbance and chromatographic retention. Only mass spectrometry distinguishes them, and hexarelin costs more than twice as much per milligram, so the substitution runs in the profitable direction.

Did 16 weeks of hexarelin build muscle?

No. IGF-1, IGFBP-3, body composition and bone mineral density were all unchanged across the full 16 weeks. Only C-terminal propeptide of type I collagen, a bone formation marker rather than an outcome, rose.

Is hexarelin banned in sport?

Yes, as "examorelin (hexarelin)" at WADA S2.2.4 under GH-releasing peptides, prohibited at all times and classified as non-specified. Searching the list for "hexarelin" alone will not return it.

Where this leaves hexarelin

Hexarelin is the best-studied compound in its class in humans, and the studies are not kind. It releases growth hormone powerfully and the release fades. It raises cortisol. It works in some populations and not in others. Its most interesting mechanism, CD36 binding in cardiac tissue, is genuinely novel and has never been shown to help a damaged human heart. These are not evidence gaps; they are findings.

That is the unusual thing about this compound. Somebody asked the questions, in people, over months, and published the answers. Most peptides sold alongside it have no equivalent record in either direction.

Browse the growth hormone peptides category, or our complete peptide guide with 118 compounds (verified August 2026). For per-injection volume, use the peptide dosing calculator alongside the reconstitution calculator. Compare shops through independent lab tests and community-verified shop reviews.

This article is for educational and informational purposes only and does not constitute medical advice. Peptides discussed may be investigational compounds not approved by the FDA (or equivalent regulators in your jurisdiction) for human use. Always consult a qualified healthcare provider before using any peptide or research compound. Peptigrity is an independent review platform and does not sell, endorse, or recommend specific products or vendors.