Hexarelin

01 · What it is

Hexarelin is a synthetic hexapeptide, His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2 — a GHRP-6 analogue in which D-tryptophan is replaced by its 2-methyl derivative ¹. Like the rest of Family C it is an agonist at the growth hormone secretagogue receptor GHS-R1a, and like the rest of Family C it releases growth hormone.

That is not the most interesting thing about it. Hexarelin also binds CD36, a scavenger receptor expressed on cardiac tissue, and CD36 has been identified as a specific cardiac receptor for hexarelin that mediates its cardioprotective effects independently of the growth hormone axis ⁸. Reviewers describing this note that hexarelin is chemically more stable and functionally more potent than ghrelin itself ⁸, and downstream work has mapped a CD36–PPARγ pathway with effects on atherosclerosis, hepatic cholesterol biosynthesis and adipose mitochondrial biogenesis ¹¹.

That makes hexarelin the only compound in this family whose principal biology may not be growth hormone at all — and it is the reason this guide gives CD36 its own section rather than a mention.

The growth hormone pharmacology is nonetheless well characterised. Hexarelin counteracts glucocorticoid-mediated inhibition of growth hormone secretion in acromegaly ¹, stimulates growth hormone release in a pituitary cell line insensitive to GHRH ⁴, and in human volunteers shows endocrine activity comparable to GHRP-2 ⁵.

What does not exist is a clinical trial. No efficacy study of hexarelin in any treatment indication was identified during preparation of this guide, in cardiology or anywhere else. The compound has a second receptor, a mechanistically distinct cardioprotective effect, animal evidence in kidney and heart — and no human outcome data.

As of September 2026 hexarelin holds no marketing authorisation from any regulator.

02 · Evidence at a glance

Evidence grade

Early Clinical — human endocrine pharmacology established; no efficacy trial

Structure

His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2; a GHRP-6 analogue ¹

Primary target

Growth hormone secretagogue receptor GHS-R1a ³

Second target

CD36 — a specific cardiac receptor mediating cardioprotection independently of growth hormone ⁸

Comparison with ghrelin

Chemically more stable and functionally more potent ⁸

Human endocrine studies

Multiple, including in acromegaly and obesity ^1,5,6

Efficacy trials in any indication

None identified

Cardiovascular human outcome data

None

Animal organ-protection data

Cardiac ^8,11 and renal ¹⁴

Antagonist behaviour

D-Lys-GHRP-6 did not block hexarelin’s endocrine response in humans ⁷

Approval status

None, any jurisdiction

03 · Mechanism of action

GHS-R1a agonism

Hexarelin binds the growth hormone secretagogue receptor and releases growth hormone through the pathway shared by this family, involving both endogenous GHRH release and somatostatin withdrawal — demonstrated for hexarelin and GHRP-6 together by antisera depletion in rats ². In a rat pituitary cell line insensitive to GHRH, hexarelin still stimulated growth hormone release, which localises part of its action to the pituitary itself rather than to hypothalamic relay alone ⁴.

CD36 — the second receptor, and the more interesting one

CD36 is a class B scavenger receptor with roles in fatty acid uptake and lipoprotein handling. It has been demonstrated as a specific cardiac receptor for hexarelin, mediating cardioprotective effects that do not require GHS-R1a and are independent of growth hormone release ⁸. Subsequent work describes a CD36–PPARγ axis through which hexarelin influences atherosclerosis, hepatic cholesterol biosynthesis and mitochondrial biogenesis in fat ¹¹.

Two receptors with different tissue distributions and different downstream biology means hexarelin is not simply a more potent GHRP-6. It is a growth hormone secretagogue that also does something else, in the heart, through a receptor none of its relatives engage. If any compound in this family deserved a development programme on mechanism alone, this is it — and it did not get one.

Resistance to glucocorticoid suppression

Glucocorticoids inhibit growth hormone secretion. Hexarelin counteracts hydrocortisone-mediated inhibition in acromegaly ¹, which distinguishes its pharmacology from GHRH-based stimulation and suggests the secretagogue pathway is less sensitive to glucocorticoid restraint.

A specific, testable pharmacological property, established in patients.

The antagonist problem

D-Lys-GHRP-6 is the canonical antagonist for this receptor family. In humans it did not modify the endocrine response to acylated ghrelin or to hexarelin at the doses tested ⁷.

A receptor model in which the antagonist does not antagonise is incomplete, and this finding sits unreconciled in the literature.

04 · Key research findings

Cardiac — the distinguishing biology. CD36 has been identified as a specific cardiac receptor for hexarelin, mediating cardioprotective effects independently of the growth hormone secretagogue receptor, with hexarelin described as chemically more stable and functionally more potent than ghrelin ⁸. The CD36–PPARγ pathway has since been characterised in metabolic disorders, covering atherosclerosis, hepatic cholesterol biosynthesis and fat mitochondrial biogenesis ¹¹.

Mechanistically the most substantial finding in Family C, and entirely preclinical.

Renal. Hexarelin alleviated apoptosis in ischaemic acute kidney injury via the MDM2/p53 pathway ¹⁴.

A second organ-protection finding through a defined molecular pathway, again in animals. The parallel with GHRP-6’s hydrogel work in the same indication suggests organ protection may be a class property worth investigating on its own terms.

Endocrine, in patients. Hexarelin counteracted the inhibitory effect of hydrocortisone on growth hormone secretion in acromegaly ¹. In obesity, hexarelin and GHRP-6 elicited growth hormone responses greater than GHRH but lower than in lean subjects ⁶. In healthy volunteers, hexarelin, GHRP-2 and an octapeptide analogue showed comparable endocrine activities and comparable time to peak ⁵.

Careful human endocrine work spanning three clinical populations, none of it measuring an outcome.

Pituitary-level action. Hexarelin stimulated growth hormone release in GH1 rat pituitary cells insensitive to GHRH ⁴, and antisera depletion established the dual GHRH-and-somatostatin dependence of the response in vivo ².

Two experiments that pin down where and how the peptide acts.

Longevity framing. A review of ageing mechanisms listed hexarelin among the most promising leads for longevity alongside caloric restriction, target of rapamycin and sirtuins ⁹.

A review’s opinion, included because it is the origin of hexarelin’s reputation in this area and because readers will encounter the claim. It is not supported by an intervention study.

Detection. Urinary metabolites of hexarelin were characterised after nasal administration alongside the other growth hormone-releasing peptides ¹⁰, and serum stability and degradation profiles have been mapped ¹⁵.

Efficacy trials. None identified, in cardiology, endocrinology or any other indication.

05 · Evidence overview

06 · Safety profile

Human data. Acute endocrine administration in acromegaly ¹, obesity ⁶ and healthy volunteers ⁵, plus volunteer administration for metabolite characterisation ¹⁰. These studies report hormonal responses; none was designed as a safety study and none involved repeated dosing.

Class liability. Growth hormone antagonises insulin action, and glucose tolerance is the central metabolic consideration for any effective secretagogue ^12,13. Hexarelin shares the non-selectivity of GHRP-6, from which it derives structurally ^1,3.

A safety question specific to this compound. CD36 is not an incidental binding site. It participates in fatty acid uptake, lipoprotein handling and inflammatory signalling across multiple tissues, and the CD36–PPARγ axis has documented roles in atherosclerosis and hepatic cholesterol biosynthesis ¹¹. A compound that engages a receptor with that range of metabolic functions has more ways to produce an unintended effect than one acting on GHS-R1a alone, and no study has characterised what sustained CD36 engagement by hexarelin does in a human.

What is genuinely unknown. Repeated administration in humans, at any dose, for any duration. Chronic CD36 engagement and its metabolic consequences. Whether the cardioprotective findings in animals transfer, and whether they would be beneficial or harmful in a person with existing cardiovascular disease — untested in either direction. Toxicology of any kind: no repeat-dose, genotoxicity, reproductive or carcinogenicity programme was identified. Immunogenicity, unassessed.

07 · US regulatory status

Current as of 6 September 2026. Hexarelin is not approved as a drug in the United States or any other jurisdiction, and is not a controlled substance.

Hexarelin does not appear by name in FDA’s category 2 bulk drug substances tables, and it was not among the seven substances reviewed by the Pharmacy Compounding Advisory Committee in July 2026 ¹⁶. Its close relatives GHRP-2 and GHRP-6 were placed in category 2 for 503B compounding in September 2023 ¹⁷.

The absence of a hexarelin entry reflects nomination history rather than a favourable assessment — no agency evidence review of this compound exists.

Under the World Anti-Doping Code, growth hormone secretagogues are prohibited at all times, and urinary detection methods covering hexarelin have been published ¹⁰. Competitors should consult the current Prohibited List directly rather than rely on secondary summaries, including this one.

08 · Limitations of the evidence

1. No efficacy trial exists in any indication. The cardioprotective findings that make this compound interesting are entirely preclinical ^8,11,14. Nothing has been tested in a person for an outcome.
2. The CD36 findings are the strongest reason to study hexarelin and the weakest reason to use it. A second receptor mediating growth hormone-independent cardioprotection ⁸ is a genuine mechanistic result and an argument for a development programme, not a substitute for one.
3. All human data are acute and endocrine. Three populations, single administrations, hormonal endpoints ^1,5,6. Nothing addresses repeated dosing.
4. Non-selectivity carries over from GHRP-6. As a structural analogue ¹, hexarelin shares the adrenocorticotropic and cortisol release characterised for that compound ³, and no study has quantified this for hexarelin under sustained administration.
5. A second receptor is a second set of unknowns. CD36’s roles in lipid handling and inflammation ¹¹ mean off-target consequences are more plausible here than for a single-receptor agonist, and none has been examined.
6. The receptor model does not fully hold. The canonical antagonist did not block hexarelin’s endocrine effect in humans ⁷, and the literature has not resolved this.
7. No toxicology programme was identified in any species.
8. The longevity framing is a review’s assertion, not a finding. Listing hexarelin among promising longevity leads ⁹ reflects mechanistic interest and no intervention data.

09 · References

1. Giustina A, Bresciani E, Bugari G, et al. Hexarelin, a novel GHRP-6 analog, counteracts the inhibitory effect of hydrocortisone on growth hormone secretion in acromegaly. Endocr Res. 1995;21(3):569–582.

   PMID 7588427 ↗

2. Conley LK, Teik JA, Deghenghi R, et al. Mechanism of action of hexarelin and GHRP-6: analysis of the involvement of GHRH and somatostatin in the rat. Neuroendocrinology. 1995;61(1):44–50.

   PMID 7731497 ↗

3. Ghigo E, Arvat E, Muccioli G, Camanni F. Growth hormone-releasing peptides. Eur J Endocrinol. 1997;136(5):445–460.

   PMID 9186261 ↗

4. Giustina A, Bonfanti C, Licini M, Ragni G, Stefana B. Hexarelin, a novel GHRP-6 analog, stimulates growth hormone (GH) release in a GH-secreting rat cell line (GH1) insensitive to GH-releasing hormone. Regul Pept. 1997;70(1):49–54.

   PMID 9250581 ↗

5. Arvat E, Di Vito L, Lanfranco F, et al. Tyr-Ala-hexarelin, a synthetic octapeptide, possesses the same endocrine activities of hexarelin and GHRP-2 in humans. J Endocrinol Invest. 1999;22(2):91–97.

   PMID 10195374 ↗

6. Scacchi M, Pincelli AI, Cavagnini F. Growth hormone in obesity. Int J Obes Relat Metab Disord. 1999;23(3):260–271.

   PMID 10193871 ↗

7. Benso A, Prodam F, Lucatello B, et al. d-Lys-GHRP-6 does not modify the endocrine response to acylated ghrelin or hexarelin in humans. Neuropeptides. 2007;41(1):45–49.

   PMID 17112585 ↗

8. Mao Y, Tokudome T, Kishimoto I. The cardiovascular action of hexarelin. J Geriatr Cardiol. 2014;11(3):253–258.

   PMID 25278975 ↗

9. Kolovou GD, Kolovou V, Mavrogeni S. We are ageing. Biomed Res Int. 2014;2014:808307.

   PMID 25045704 ↗

10. Semenistaya E, Zvereva I, Thomas A, Thevis M, Krotov G, Rodchenkov G. Determination of growth hormone releasing peptides metabolites in human urine after nasal administration of GHRP-1, GHRP-2, GHRP-6, hexarelin, and ipamorelin. Drug Test Anal. 2015;7(10):919–925.

    PMID 25869809 ↗

11. Maréchal L, Laviolette M, Rodrigue-Way A, et al. The CD36-PPARγ pathway in metabolic disorders. Int J Mol Sci. 2018;19(5):1529.

    PMID 29883404 ↗

12. Sigalos JT, Pastuszak AW. The safety and efficacy of growth hormone secretagogues. Sex Med Rev. 2018;6(1):45–53.

    PMID 28400207 ↗

13. Sinha DK, Balasubramanian A, Tatem AJ, et al. Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males. Transl Androl Urol. 2020;9(Suppl 2):S149–S159.

    PMID 32257855 ↗

14. Guan C, Li C, Shen X, et al. Hexarelin alleviates apoptosis on ischemic acute kidney injury via MDM2/p53 pathway. Eur J Med Res. 2023;28(1):344.

    PMID 37710348 ↗

15. González-López NM, Guerra-Acero-Turizo LM, Blanco-Medina I, et al. In-house standards derived from doping peptides: enzymatic and serum stability and degradation profile of GHRP and GHRH-related peptides. Biomed Chromatogr. 2023;37(12):e5741.

    PMID 37688464 ↗

16. US Food and Drug Administration. July 23–24, 2026: Meeting of the Pharmacy Compounding Advisory Committee. Docket FDA-2025-N-6895. Regulatory document; no PMID.

    Source ↗

17. US Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. Page current as of 22 April 2026. Regulatory document; no PMID.

    Source ↗