The evidence base for hexarelin includes endocrine and exploratory cardiovascular research, but it has not matured into an FDA-approved product. The clinical record is too limited for broad consumer claims about performance, recovery, or aging.
Physicians may submit patient-specific prescription requests for hexarelin for pharmacy review. Certain preparations may be available now when clinically appropriate, lawfully prescribed, supported by patient-specific documentation, and approved by the dispensing pharmacy. Availability is determined case by case. This is not a consumer access promise; it is a clinical, sourcing, formulation, and regulatory review process. This ingredient is part of an evolving FDA review process for peptide-related bulk substances used in compounding.
Patient-specific pharmacy review keeps hexarelin requests attached to a prescriber, an identified patient, and a formulation decision rather than to a direct-to-consumer peptide protocol.
In brief
Hexarelin Explained
Hexarelin is a synthetic six-amino-acid peptide developed in the 1990s by an Italian pharmaceutical company (Mediolanum Farmaceutici) to stimulate growth hormone release from the pituitary 1220. It works through the same receptor used by the natural hormone ghrelin, and it was studied in small trials as a possible diagnostic tool for growth hormone deficiency and as a candidate growth hormone-axis therapy. Clinical development was not completed and no FDA-approved product exists.
Hexarelin has no FDA approval in the United States. This ingredient is part of an evolving FDA review process. Physicians may submit patient-specific prescription requests for pharmacy review. Availability is determined case by case, and availability may change after FDA review, PCAC discussion, final agency action, or state-board guidance.
Hexarelin, His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2; a six-amino-acid synthetic peptide closely related to GHRP-6 and GHRP-2
Branded products
None. Hexarelin (originally Mediolanum Farmaceutici, Italy; investigational code MF-6003) was developed in the 1990s and did not reach FDA approval.
Evidence posture
Small phase 1 and phase 2 human studies of GH-releasing pharmacology and diagnostic use in growth hormone deficiency [imbimbo1994, ghigo1994, loche1995_jcem]; preclinical cardiac and CD36 biology [locatelli1999, bodart2002]. No phase 3 program. Discontinued in clinical development.
FDA-approval status
Category 2, evolving FDA review process. Valid patient-specific prescription required; supporting clinical rationale may be requested.
FDA bulks list status
Category 2, evolving FDA review process. Valid patient-specific prescription required; supporting clinical rationale may be requested.
RonanRx compounding status
Physicians may submit patient-specific prescription requests for pharmacy review. Availability is determined case by case.
WADA status
Category 2, evolving FDA review process. Valid patient-specific prescription required; supporting clinical rationale may be requested.
Prescription review
Patient-Specific Prescription Only
Physicians may submit patient-specific prescription requests for Hexarelin for pharmacy review. Certain preparations may be available now when clinically appropriate, lawfully prescribed, and approved by the dispensing pharmacy. Availability is determined case by case.
Made to order, not off a shelf. No batch sits in a warehouse waiting for buyers. Your prescription is what triggers the prep.
Named-patient label. The bottle carries your name. The batch records carry your prescription.
Dose, strength, and route chosen for you. A prescriber who knows your chart decides what gets compounded, not a manufacturer who set the strength for a trial population.
Licensed pharmacist on the hook. A real person, with a license that can be pulled, signs off on every prep. State inspectors check the facility.
Compounded drugs are not FDA-approved. They should not be evaluated using branded-drug trial data. Availability varies by state and prescribed medication.
A research-use-only website ships a vial from a warehouse. There is no prescription, no pharmacist, no facility inspection, and no way to recall the product if something is wrong with it. If the vial is mislabeled, contaminated, or under-potent, there is nobody whose license is at stake.
A 503A compounding pharmacy is the other thing. Your doctor writes the prescription. A licensed pharmacist, whose name is on the label, prepares the medicine in a facility the state inspects. If something goes wrong, there is a person and a license on the hook, and a documented chain of custody on every lot. That accountability is what makes it safe.
What it is
What is Hexarelin?
Hexarelin is a synthetic hexapeptide with the sequence His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2. Structurally it is a close analog of growth hormone-releasing peptide-6 (GHRP-6), with a methylated tryptophan residue at position 2 that increases potency and metabolic stability. It was developed by Mediolanum Farmaceutici S.p.A. in Italy as compound MF-6003 1 and is sometimes referred to in the older literature by that code or as 'Hex.'
Hexarelin was studied in the 1990s for two related purposes: as a candidate therapy for growth hormone deficiency (oral, intranasal, and parenteral formulations were investigated) and as a pharmacologic probe of the then-uncharacterized growth hormone secretagogue receptor 21. After the cloning of the GHS-R1a receptor by Howard and colleagues at Merck in 1996 20 and the discovery of its endogenous ligand ghrelin by Kojima and colleagues in 1999, hexarelin retained value primarily as a research tool. Phase 2 clinical development was not advanced to phase 3 and the compound has no FDA-approved indication.
Hexarelin is not commercially available as a manufactured drug product. Reference standard material is sold for analytical and research use. The compound is included on the WADA Prohibited List as a peptide hormone secretagogue and is detected in anti-doping urine screens that target the GHRP class 283029.
How it works
How Hexarelin Works
Class
GH-secretagogue hexapeptide
First studied
1990s
Current status
Category 2, evolving FDA review process
Compounding category
Patient-specific 503A on physician request, pending broader FDA review
Hexarelin binds and activates the growth hormone secretagogue receptor type 1a (GHS-R1a), a seven-transmembrane G-protein-coupled receptor expressed in the anterior pituitary somatotrope and in hypothalamic neurons, with downstream signaling through Gq/11, phospholipase C, inositol trisphosphate, and intracellular calcium release 20213. The result in vivo is rapid pulsatile growth hormone release from the somatotrope, distinct from and complementary to the GHRH-mediated cAMP pathway 6413.
Pituitary GH responses to hexarelin are potentiated when co-administered with GHRH, supporting a model in which hexarelin acts in part by augmenting GHRH tone and in part by directly stimulating the somatotrope 5615. Somatostatin opposes the response and explains a portion of the variability observed across populations and physiologic states 414. Aging, obesity, glucocorticoid excess, and post-menopausal estrogen deficiency each attenuate the GH response, patterns characterized in the 1990s Turin, Sardinia, and Brescia centers and replicated across small cohorts.
A second and pharmacologically separable receptor interaction occurs at CD36, a scavenger receptor expressed on cardiomyocytes, macrophages, and microvascular endothelium 25. CD36 binding by hexarelin and other GHRP-family peptides is implicated in cardiac and vascular effects observed in rat models, effects that occur independent of pituitary GH release and that are not reproduced by selective GHS-R1a agonists such as ipamorelin 222527. This receptor-level dual activity is the principal pharmacologic distinction between hexarelin and the selective GHS-R1a agonist class 7178.
Research history
Hexarelin Research History
Hexarelin (MF-6003) was developed at Mediolanum Farmaceutici (Milan, Italy) in the late 1980s and early 1990s as a more potent and metabolically stable analog of the prototype growth hormone-releasing peptide GHRP-6, by introduction of a 2-methyl substitution on the D-tryptophan at position 2 73. The first human pharmacology was reported by Imbimbo, Mant, and Edwards in 1994 in Eur J Clin Pharmacol as a dose-response study in healthy adult men, establishing dose-dependent GH release after intravenous and subcutaneous administration 1. Ghigo, Arvat, and colleagues in Turin reported the comparative pharmacology of intravenous, subcutaneous, intranasal, and oral hexarelin in 1994 in J Clin Endocrinol Metab, establishing intranasal and (lower-bioavailability) oral routes as feasible 2815.
Through the mid-1990s a series of small mechanistic and population-level studies characterized: the synergy of hexarelin with GHRH and the opposing role of somatostatin 654; the metabolic, sex-steroid, glucocorticoid, and obesity modifiers of the GH response; reproducibility and sex-steroid effects in children 12; diagnostic performance for growth hormone deficiency in children and in patients with hypothalamic-pituitary disease 91018; and day-night patterns of GH responsiveness in normal adults 11. Short-term intranasal or oral dosing in human aging did not produce GHRP-class desensitization at the 1, 2 week scale 13. The TRH-stimulated TSH response was not altered by hexarelin co-administration in normal men 19, distinguishing the GH-axis effect from broader anterior pituitary stimulation 17.
The receptor was cloned in 1996 by Howard and colleagues at Merck and named the growth hormone secretagogue receptor (GHS-R), the assay used hexarelin-related ligands 20. The endogenous ligand of GHS-R was identified by Kojima and colleagues in 1999 as the acylated peptide ghrelin, recasting the GHRP class, including hexarelin, as ghrelin mimetics 21. Concurrently, Locatelli and colleagues in Milan reported GH-independent cardioprotective effects of hexarelin in the rat in 1999 22, followed by Rossoni 2000 (isolated rat heart ventricular dysfunction) 23, Torsello 2001 (calcium deprivation/replenishment injury) 24, and Bodart and colleagues in 2002 identifying CD36 as the mediating receptor in the heart 25. Cao and colleagues reviewed the cardiac and vascular pharmacology of hexarelin and other GHRPs in 2006 27.
Phase 2 clinical development of hexarelin for growth hormone deficiency and for cardiac indications was not advanced to phase 3. No FDA-approved product reached market. The GH-secretagogue class subsequently moved toward the selective GHS-R1a agonist ipamorelin and the orally active small-molecule MK-677 (ibutamoren) for non-FDA-approved investigational use, and toward macimorelin (FDA-approved 2017) as a GHRH/secretagogue-based stimulation test for adult growth hormone deficiency. Hexarelin remained available only as a research-grade peptide and as a doping agent of concern: anti-doping methods for hexarelin and its metabolites in human urine were developed in the mid-2000s 28 and refined for screening assays in the 2010s 293031.
Timeline
Hexarelin Timeline
1994Imbimbo, Mant, and Edwards publish the first human dose-response study of hexarelin (Mediolanum MF-6003) in Eur J Clin Pharmacol 1
1994Ghigo, Arvat, and colleagues (Turin) report comparative GH-releasing activity of intravenous, subcutaneous, intranasal, and oral hexarelin in JCEM 2
1994Arvat et al 3. (JCEM) demonstrate that arginine and GHRH restore the blunted hexarelin GH response in elderly subjects
1995Conley et al 4. (Neuroendocrinology) characterize the involvement of GHRH and somatostatin in the mechanism of action of hexarelin and GHRP-6 in rats
1995Arvat et al 5. (Neuroendocrinology) characterize modulation of the GH-releasing activity of hexarelin in man
1995Giustina et al 67. (J Endocrinol) compare hexarelin and GHRH on GH secretion; (Endocr Res) show hexarelin counteracts hydrocortisone-induced GH suppression in acromegaly
1995Loche et al 910. (JCEM, two papers) report the GH-releasing activity of hexarelin in short normal and obese children and in GH-deficient patients, diagnostic use established at small scale
1995Maccario et al 8. (Metabolism) characterize metabolic modulation (glucose, free fatty acids) of the hexarelin GH response in man
1996Howard, Feighner, and colleagues at Merck clone the growth hormone secretagogue receptor (GHS-R) using hexarelin-related ligands; published in Science 20
1996Torsello et al 14. (Eur J Endocrinol) characterize the mechanism of action of hexarelin in the rat, pituitary and hypothalamic sites of action
1996Ghigo et al 13. (Eur J Endocrinol) show short-term intranasal or oral hexarelin does not desensitize GH responsiveness in aging adults
1996Grottoli et al 15. (Eur J Endocrinol) demonstrate that somatotrope responsiveness to hexarelin is refractory to glucose-induced inhibition in obesity
1996Ciccarelli et al 16. (Clin Endocrinol) show hexarelin stimulates prolactin secretion in acromegaly but not in hyperprolactinemia
1997Loche et al 11. (Clin Endocrinol) report that hexarelin stimulates GH secretion during day and night in normal men
1997Arvat et al 17. (Eur J Endocrinol) report that oestrogen replacement does not restore the reduced GH-releasing activity of hexarelin in post-menopausal women
1997Loche et al 12. (JCEM) report reproducibility and effect of sex steroids on the hexarelin GH response in children
1998Maghnie et al 18. (JCEM) characterize the hexarelin GH response in patients with different hypothalamic-pituitary abnormalities, diagnostic positioning vs GHRH-arginine
1998Arosio et al 19. (J Endocrinol Invest) confirm that hexarelin does not alter the TRH-induced TSH response in normal adult men
1999Kojima and colleagues identify ghrelin as the endogenous ligand of GHS-R1a, reframing hexarelin and the GHRP class as ghrelin mimetics; Smith et al 21. (Horm Res) review GHS types and receptors
1999Locatelli et al 22. (Endocrinology) demonstrate GH-independent cardioprotective effects of hexarelin in the rat, preserved in hypophysectomized animals
2000Rossoni et al 23. (Pharmacol Res) show hexarelin protects the isolated rat heart from ventricular dysfunction produced by calcium-free perfusion
2001Torsello et al 24. (Endocrine) report hexarelin (but not GH) protects heart from damage induced in vitro by calcium deprivation and replenishment
2002Bodart et al 25. (Circ Res) identify CD36 as the receptor mediating cardiovascular actions of GHRP-family peptides including hexarelin, separable from GHS-R1a
2002Maccario et al 26. (Eur J Endocrinol) characterize the impact of two or three daily subcutaneous injections of hexarelin on 24-h GH, prolactin, ACTH, and cortisol secretion
2006Cao et al 27. (Trends Endocrinol Metab) review the cardiovascular effects of ghrelin and synthetic GH secretagogues including hexarelin
2006Thevis et al 28. (RCM) publish anti-doping detection methods for therapeutic GH secretagogue activity including hexarelin metabolites in urine
2010Thomas et al 29. (Drug Test Anal) report identification of GHRP-2 in a nutritional supplement, highlighting non-clinical channels for the GHRP class
2015Semenistaya et al. (Drug Test Anal) characterize urinary metabolites of GHRP-1, GHRP-2, GHRP-6, hexarelin, and ipamorelin after nasal administration; Esposito et al 3031. (J Pept Sci) report in vitro metabolic models for sport drug testing
2024FDA places hexarelin in Category 2 of the 503A bulk drug substances list, under FDA review pending resolution of agency-identified concerns; RonanRx moves physician-submitted requests through patient-specific pharmacy review 3233
Natural role
Biological Role of Hexarelin
Growth hormone secretagogue receptor type 1a (GHS-R1a) is expressed in the anterior pituitary somatotrope, the hypothalamic arcuate nucleus, and several peripheral tissues. Its endogenous ligand is the acylated peptide hormone ghrelin, secreted primarily by the gastric oxyntic mucosa, which regulates pulsatile growth hormone release, appetite, and energy homeostasis 21. Synthetic ghrelin mimetics, including the GHRP-family peptides hexarelin, GHRP-6, GHRP-2, and ipamorelin, and the orally active non-peptide MK-677, bind GHS-R1a with affinities comparable to ghrelin and reproduce a subset of its central and peripheral effects.
Hexarelin's pharmacology is dual: it is an agonist at GHS-R1a and a separate ligand at the scavenger receptor CD36. CD36 is expressed on cardiomyocytes, monocyte-macrophages, microvascular endothelium, and adipocytes, and is implicated in long-chain fatty acid transport, oxidized-LDL handling, and innate immune signaling. The CD36 interaction at the heart is the principal pharmacologic distinction between hexarelin (and several other GHRP-family peptides) and the selective GHS-R1a agonist ipamorelin, which does not bind CD36 with comparable affinity 2527.
Clinical contexts studied
Clinical Contexts for Hexarelin
Diagnosis of growth hormone deficiency (research/diagnostic use) emerging
Studied in small acute-stimulation trials in children and adults in the 1990s. Not adopted as a standard diagnostic stimulus; no FDA approval.
Hexarelin produced reproducible GH release at 1.5, 2 μg/kg subcutaneously or intravenously in normal adults and children. Loche et al. characterized the GH response in short normal and obese children and in hypopituitary patients 9, and a separate paper compared GH-deficient and normal pediatric responses 10. Maghnie et al. characterized differential responses across organic hypothalamic-pituitary lesions vs idiopathic GHD 18. Reproducibility and sex-steroid modulation in pediatric populations were reported by Loche et al. 12. Subsequent diagnostic practice moved to the GHRH-arginine and (FDA-approved 2017) macimorelin tests rather than hexarelin.
Investigated in small phase 1/2 studies; phase 3 development was not completed and no FDA-approved product exists.
Short-term subcutaneous, intranasal, and oral hexarelin produced dose-dependent GH release in healthy adults and in children with GH deficiency 1210. The Ghigo aging substudy demonstrated absence of GHRP-class desensitization across 1, 2 week intranasal and oral schedules in older adults 13. Larger and longer trials of clinically meaningful endpoints (growth velocity in children, IGF-1 normalization, body composition in adults) were not completed and the compound did not progress to FDA approval. Selective GHS-R1a agonists (ipamorelin) and the orally active small-molecule MK-677 have since been the focus of investigational use in the GH-axis space.
Cardiac ischemia/reperfusion and post-ischemic ventricular dysfunction (preclinical only) preclinical
Preclinical only. Rat in vitro and in vivo evidence of GH-independent cardioprotection. Not studied in completed human cardiovascular trials.
In isolated rat heart and in vivo rat models, hexarelin produced preservation of post-ischemic left-ventricular function, reduction in infarct size, and modulation of cardiomyocyte injury markers 222324. The protective effect persisted in hypophysectomized animals, dissociating it from pituitary GH release 22. Bodart et al. identified CD36 as the cardiac receptor mediating these effects of GHRP-family peptides 25. Cao et al. reviewed the cardiovascular pharmacology of ghrelin and synthetic GH secretagogues including hexarelin 27. No completed human cardiovascular efficacy or safety trial has tested these preclinical observations in patients.
FDA-approved use
FDA-Approved Uses of Hexarelin
Hexarelin has no FDA approval in the United States. This ingredient is part of an evolving FDA review process. Physicians may submit patient-specific prescription requests for pharmacy review. Availability is determined case by case, and availability may change after FDA review, PCAC discussion, final agency action, or state-board guidance.
Hexarelin is prohibited at all times in competitive sport under section S2 of the World Anti-Doping Agency Prohibited List (Peptide Hormones, Growth Factors, Related Substances and Mimetics) 36. Urinary detection methods for hexarelin and its metabolites are established as routine WADA-accredited laboratory practice 2830.
Compounded use
Compounded Hexarelin (503A)
Physicians may submit patient-specific prescription requests for pharmacy review. For hexarelin, certain preparations may be available now when clinically appropriate, lawfully prescribed, and approved by the dispensing pharmacy. Availability is determined case by case and may depend on patient-specific documentation, ingredient status, source qualification, formulation feasibility, state requirements, and pharmacist judgment. The review starts with the evidence constraint: The evidence base for hexarelin includes endocrine and exploratory cardiovascular research, but it has not matured into an FDA-approved product. The clinical record is too limited for broad consumer claims about performance, recovery, or aging.
This ingredient is part of an evolving FDA review process. RonanRx is monitoring FDA's PCAC process and any subsequent agency action. This ingredient is part of an evolving FDA review process for peptide-related bulk substances used in compounding. Availability may change after FDA review, PCAC discussion, final agency action, or state-board guidance. For hexarelin, RonanRx ties that monitoring to the evidence limits described above and to any patient-specific documentation submitted by the prescriber.
Valid patient-specific prescription required. Supporting clinical rationale may be requested. Compounded medications are not FDA-approved. No consumer self-ordering, no office stock, no bulk dispensing. Requests for hexarelin are reviewed before any preparation is made or released. Patient-specific pharmacy review keeps hexarelin requests attached to a prescriber, an identified patient, and a formulation decision rather than to a direct-to-consumer peptide protocol.
Formulations and routes
Hexarelin Formulations and Routes
Form
Concentration
Description
No FDA-approved manufactured product
Not applicable
If a patient-specific hexarelin request is approved after pharmacy review, the route and formulation must be selected by the prescriber and dispensing pharmacy for that named patient. Research-use presentations sold online are not RonanRx preparations.21
Routes used in published literature: subcutaneous, intravenous, intranasal, oral.
Oral hexarelin was studied at higher doses than parenteral routes due to substantially lower bioavailability; comparative dose-equivalence was characterized in the 1994 JCEM route-comparison paper
RonanRx does not publish a consumer dosing schedule for hexarelin. Any request requires a valid patient-specific prescription, supporting clinical rationale, and pharmacist review. Route, strength, dosing interval, monitoring expectations, and dispensing quantity would be determined case by case from the prescriber's documentation and pharmacy feasibility review.
Clinicians whose patients are using research-grade hexarelin obtained outside the regulated pharmacy supply chain should be aware that potency, identity, and sterility of such material are not characterized, and that doses cited in 1990s phase 1 studies cannot be safely extrapolated to material of unknown origin 1232.
Doses listed are literature context, not patient instructions. Dosing decisions are made by the prescribing doctor and tailored to the individual patient.
Safety
Hexarelin Safety
Safety overview
Acute human safety data for hexarelin are limited to the small phase 1 and phase 2 cohorts published in the 1990s. In those studies, single-dose intravenous, subcutaneous, intranasal, and oral hexarelin at doses of approximately 1.5, 2.0 μg/kg parenteral or higher intranasal/oral were generally well tolerated in healthy adults and in children with growth hormone deficiency, with the most commonly reported acute effects being transient mild facial flushing, mild and brief somnolence, and a brief sensation of nasal irritation with intranasal dosing 12. Repeated subcutaneous dosing over 1, 4 weeks produced acute attenuation of the GH response in some protocols, while short-term intranasal or oral dosing in aging adults did not produce comparable desensitization 1326.
Acute hexarelin administration produces modest dose-dependent rises in prolactin, ACTH, and cortisol secretion in addition to GH release 1626. The TRH-induced TSH response is unaffected by hexarelin co-administration 19. The long-term endocrine, metabolic, cardiovascular, and oncologic safety profile of hexarelin in humans has not been characterized in completed phase 3 trials. Preclinical cardiac data showing CD36-mediated effects 2522 have not been translated into completed human cardiovascular safety studies.
Because Physicians may submit patient-specific prescription requests for pharmacy review. Availability is determined case by case. Patients using research-grade hexarelin obtained outside the licensed pharmacy supply chain are exposed to material of uncharacterized identity, potency, sterility, and endotoxin content 32.
Contraindications
Hexarelin has no FDA-approved label and therefore no labeled contraindications. Investigational use in the 1990s typically excluded patients with active malignancy, uncontrolled cardiovascular or cerebrovascular disease, severe hepatic or renal impairment, active proliferative diabetic retinopathy, pregnancy or lactation, and known hypersensitivity to peptide preparations. These exclusions reflect general phase 1/2 GH-axis trial practice rather than a hexarelin-specific safety signal.
Hexarelin is prohibited at all times in competitive sport under WADA section S2; athletes subject to anti-doping testing should not use hexarelin in any form 1236.
Drug interactions
Hexarelin co-administered with GHRH augments the GH response above either agent alone 56. Somatostatin and somatostatin analogs blunt the response 4. Glucocorticoids (hydrocortisone) suppress the GH response; hexarelin partially counteracts this in acromegaly 7. Insulin-induced hypoglycemia and arginine each modify the response in patterns characterized for the broader GHRP class 38. Estrogen status in post-menopausal women does not appear to restore the age-attenuated response 17. None of these are FDA-labeled interactions because hexarelin is not FDA-approved.
Drug-metabolizing enzyme interactions have not been formally characterized. Hexarelin is a small peptide cleared primarily by proteolysis and is not expected to be a substrate or inhibitor of cytochrome P450 enzymes.
Adverse events
Across the small 1990s phase 1 and phase 2 studies, predominantly single-center academic cohorts of healthy adults and pediatric patients with GH deficiency, adverse events reported with hexarelin were limited to transient mild facial flushing, brief somnolence, mild nasal irritation with intranasal dosing, and minor injection-site reactions with subcutaneous dosing 210. Acute changes in prolactin, ACTH, and cortisol were of small magnitude and not labeled as clinically meaningful in the source papers 1626. No serious adverse events were reported in the phase 1 dose-response or comparative-route studies in healthy adults 1.
The cumulative human exposure base is small relative to FDA-approved peptide therapeutics, and long-term cardiovascular, metabolic, and oncologic outcome data are absent. Because Physicians may submit patient-specific prescription requests for pharmacy review. Availability is determined case by case.
Monitoring
Monitoring Hexarelin Therapy
No FDA-labeled monitoring schedule exists. Phase 1/2 research studies of hexarelin in adults and children measured serum GH every 15, 30 minutes for 90, 180 minutes after dosing and assessed prolactin, ACTH, cortisol, and IGF-1 as indicated 129. The diagnostic-utility studies used 90-minute or 120-minute peak GH as the analytic endpoint 26.
Special populations
Hexarelin in Special Populations
Pregnancy
Hexarelin has not been studied in pregnant patients. Phase 1/2 trials excluded pregnant participants. No FDA-labeled pregnancy category exists because the compound is not FDA-approved.
Lactation
Hexarelin has not been studied during lactation. No data are available on transfer into human milk or effects on the breastfed infant.
Pediatric
Hexarelin was studied as a GH-releasing stimulus in children with short stature, obesity, and growth hormone deficiency in small academic cohorts in the 1990s 91012. Reproducibility, sex-steroid modulation, and differential responses across organic and idiopathic GH-deficiency phenotypes were characterized at small scale. These studies did not establish hexarelin as a treatment for pediatric GH deficiency and the compound did not reach FDA approval for any pediatric indication 18.
Geriatric
The GH response to hexarelin is attenuated in older adults relative to younger adults 313. Arginine and GHRH co-administration partially restore the response 3. Short-term (1, 2 week) intranasal or oral hexarelin in aging adults did not produce GHRP-class desensitization at the time points studied 13.
Renal impairment
Hexarelin pharmacokinetics in renal impairment have not been formally characterized. Hexarelin is a small peptide cleared by proteolysis; renal clearance is a minor contributor to overall elimination.
Hepatic impairment
Hexarelin pharmacokinetics in hepatic impairment have not been formally characterized.
Evidence quality
Hexarelin Evidence Quality
The human evidence base for hexarelin consists of approximately a dozen small phase 1 and phase 2 academic cohorts published between 1994 and approximately 2002, conducted predominantly at single Italian centers (Turin, Cagliari/Sardinia, Milan, Brescia), with sample sizes typically 6, 40 participants per study 101826. Endpoints were short-term GH, prolactin, ACTH, and cortisol pharmacodynamics, and, in pediatric cohorts, diagnostic performance for growth hormone deficiency 129. None of these studies were powered for clinical efficacy or long-term safety endpoints.
Mechanistic evidence is stronger. The Howard et al. cloning of GHS-R using hexarelin-related ligands 20 and the subsequent identification of ghrelin as the endogenous ligand 21 situate hexarelin within a well-characterized receptor system 22. The Bodart et al. identification of CD36 as the cardiac receptor for GHRP-family peptides 25 and the supporting preclinical cardioprotection literature establish a biologically plausible second mechanism of action. None of this cardiac biology has been translated into completed human cardiovascular efficacy trials 27.
There is no phase 3 evidence for any clinical indication. No FDA-approved manufactured product exists. Physicians may submit patient-specific prescription requests for pharmacy review. Availability is determined case by case. This brief documents the available evidence for clinician awareness only and should not be interpreted as a clinical recommendation.
Phase 1, single-dose, dose-response of hexarelin in healthy adult men
—
Acute (90, 180 minute GH sampling)
Established dose-dependent GH release after intravenous and subcutaneous hexarelin; defined the 1.5, 2.0 μg/kg parenteral dose range used in subsequent academic studies 1
Phase 1 comparative pharmacology of intravenous, subcutaneous, intranasal, and oral hexarelin in healthy adults
—
—
Characterized relative bioavailability and acute GH-releasing potency across four routes; intranasal hexarelin produced reproducible GH release at ~10-fold the parenteral per-kg dose; oral bioavailability substantially lower 2
Preclinical mechanistic study of hexarelin and GHRP-6 in rats, involving GHRH and somatostatin
—
—
Demonstrated that the GH response to hexarelin and GHRP-6 involves both endogenous GHRH and somatostatin pathways; supports the hypothalamic component of the mechanism 4
Molecular cloning of the growth hormone secretagogue receptor using hexarelin-related ligands as the orphan-receptor probe
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—
Identified the 7-transmembrane GPCR (GHS-R1a) responsible for the pituitary and hypothalamic actions of hexarelin and the GHRP class; foundational paper for the field that subsequently identified ghrelin as the endogenous ligand 20
Preclinical isolated rat heart and in vivo rat ischemia model, including hypophysectomized animals
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—
Hexarelin produced GH-independent cardioprotective effects in the rat; the protective effect persisted in hypophysectomized animals, dissociating the cardiac effect from pituitary GH release 22
Preclinical isolated rat heart model of calcium deprivation/replenishment injury
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—
Hexarelin (but not growth hormone) protected isolated rat heart from calcium-paradox damage; further dissociation from a pituitary-GH-mediated mechanism 24
Preclinical receptor-binding and signaling study identifying the cardiac receptor for GHRP-family peptides
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—
Identified CD36 as the receptor mediating cardiovascular actions of hexarelin and other GHRP-family peptides; established the dual-receptor pharmacology that distinguishes hexarelin from selective GHS-R1a agonists 25
Repeated subcutaneous hexarelin (2 or 3 injections/day) with 24-hour endocrine profiling
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—
Characterized the impact of repeated daily subcutaneous hexarelin on 24-h GH, prolactin, ACTH, and cortisol secretion; documented partial desensitization patterns over short-term repeated dosing 26
Anti-doping mass spectrometry study characterizing urinary metabolites of GHRP-1, GHRP-2, GHRP-6, hexarelin, and ipamorelin after nasal administration
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Established detection methods used in WADA-accredited laboratory practice for hexarelin and other GHRP-class peptides 30
Mechanism detail
Detailed Mechanism of Hexarelin
GHS-R1a is a class A G-protein-coupled receptor identified through cloning work by Howard and colleagues at Merck in 1996 using a hexarelin-related ligand as the orphan-receptor probe 20. The receptor binds the endogenous octanoylated peptide ghrelin (identified by Kojima and colleagues in 1999) and several synthetic small-molecule and peptide agonists including hexarelin, GHRP-6, GHRP-2, ipamorelin, and the orally active non-peptide MK-677 2127. Signaling proceeds principally through Gq/11 with downstream phospholipase C activation, IP3 generation, and somatotrope calcium mobilization; β-arrestin recruitment and Gi/o coupling occur to variable degrees across ligands and contribute to differences in functional selectivity.
In rat in vivo and pituitary cell models, Torsello and colleagues characterized hexarelin as a more potent and longer-acting GH-releasing peptide than GHRP-6, with activity at both pituitary and hypothalamic sites 14. In humans, the GH response to hexarelin is reproducibly larger than that to GHRH alone and is augmented by GHRH co-administration, consistent with a partly hypothalamic mechanism 65. Glucocorticoids blunt the GH response, Giustina et al. 1995 demonstrated that hexarelin partially counteracts hydrocortisone-induced suppression of GH secretion in acromegaly, providing pharmacologic evidence for the somatostatin-opposed model 74.
Acute hexarelin administration also produces modest, dose-dependent rises in prolactin, ACTH, and cortisol secretion that are not observed (or are smaller) with selective GHS-R1a agonists such as ipamorelin and that are interpreted as reflecting either off-target hypothalamic action or partial GHS-R1a-independent effects 1626. Repeated subcutaneous dosing in healthy adults attenuates the GH response over days to weeks (the GHRP-class desensitization phenomenon), although short-term intranasal or oral dosing in aging adults does not produce a comparable reduction across 1, 2 week schedules 1326. Thyrotropin and gonadotropin axes are not appreciably affected by acute hexarelin 19.
CD36 is a class B scavenger receptor with high affinity for thrombospondin, oxidized LDL, long-chain fatty acids, and, as Bodart and colleagues demonstrated in 2002, for hexarelin and structurally related GHRP-family peptides 25. Cardiac CD36 binding by hexarelin is associated with reduced ischemia-reperfusion injury, preserved post-ischemic left-ventricular function, and modulation of cardiomyocyte inflammatory signaling in isolated rat heart and in vivo models. The cardiac CD36 mechanism is GH-independent: Locatelli and colleagues showed that hexarelin's protective effect on the post-ischemic isolated rat heart was preserved in hypophysectomized animals, dissociating the cardiac effect from pituitary GH release 222324. None of this CD36-mediated cardiac biology has been replicated in completed phase 2 or phase 3 human cardiovascular efficacy trials with hexarelin.
Pharmacology
Hexarelin Pharmacokinetics & Pharmacodynamics
Pharmacokinetics
Hexarelin pharmacokinetics in humans were characterized in the 1990s phase 1 program. Bioavailability is high after intravenous bolus, moderate after subcutaneous injection, lower after intranasal administration, and substantially lower after oral administration; the route-comparison paper by Ghigo et al. 1994 provided the principal PK/PD reference for the program 21. The acute GH peak after a single subcutaneous dose of 1.5, 2.0 μg/kg occurs at approximately 30, 60 minutes and resolves over 2, 3 hours; plasma half-life of hexarelin itself is short (approximately 50, 70 minutes after intravenous dosing in the published phase 1 data).
Hexarelin is cleared primarily by proteolytic catabolism. Cytochrome P450 metabolism is not a significant pathway. Renal and hepatic-impairment PK have not been formally characterized.
Pharmacodynamics
Pharmacodynamic effects in humans are dominated by acute GH release from the pituitary somatotrope, with smaller dose-dependent rises in prolactin, ACTH, and cortisol 1626. The TRH-induced TSH response is not affected 19. Repeated daily subcutaneous dosing attenuates the GH response over days to weeks (the GHRP-class desensitization phenomenon), while short-term intranasal or oral dosing in aging adults does not produce comparable desensitization 132622.
Preclinical pharmacodynamic effects relevant to potential cardiac indications, including preservation of post-ischemic left-ventricular function, modulation of cardiomyocyte injury markers, and CD36-mediated signaling, are described in rat models. None of these have been characterized in completed human cardiovascular trials 232425.
Comparative formulations
Comparing Hexarelin Formulations
Hexarelin has no manufactured comparator. Among the broader synthetic GH-secretagogue class, the selective GHS-R1a agonist ipamorelin is the most commonly cited comparator: ipamorelin binds GHS-R1a with similar potency to hexarelin but does not bind CD36 with comparable affinity and produces a smaller prolactin/ACTH/cortisol response 2521. The orally active non-peptide GH secretagogue MK-677 (ibutamoren) achieves chronic GH-axis activation with once-daily oral dosing and was advanced further in clinical development than hexarelin (though also did not reach FDA approval). The FDA-approved oral GH-axis diagnostic agent macimorelin (Macrilen, 2017) supplanted hexarelin and the GHRH-arginine test as the standard pharmacologic GH-deficiency stimulus in adults for diagnostic use.
Storage
Hexarelin Storage and Handling
No FDA-approved manufactured hexarelin product exists and therefore no labeled storage recommendation. Reference standard and research-grade peptide material is typically supplied as lyophilized powder and stored at −20°C with desiccation; reconstituted solutions are not stable at room temperature for extended periods. RonanRx does not stock or compound hexarelin.
RonanRx operations
Hexarelin Compounding & Operations
503A compounding
Physicians may submit patient-specific prescription requests for pharmacy review. For hexarelin, certain preparations may be available now when clinically appropriate, lawfully prescribed, and approved by the dispensing pharmacy. Availability is determined case by case and may depend on patient-specific documentation, ingredient status, source qualification, formulation feasibility, state requirements, and pharmacist judgment. The review starts with the evidence constraint: The evidence base for hexarelin includes endocrine and exploratory cardiovascular research, but it has not matured into an FDA-approved product. The clinical record is too limited for broad consumer claims about performance, recovery, or aging.
This ingredient is part of an evolving FDA review process. RonanRx is monitoring FDA's PCAC process and any subsequent agency action. This ingredient is part of an evolving FDA review process for peptide-related bulk substances used in compounding. Availability may change after FDA review, PCAC discussion, final agency action, or state-board guidance. For hexarelin, RonanRx ties that monitoring to the evidence limits described above and to any patient-specific documentation submitted by the prescriber.
Valid patient-specific prescription required. Supporting clinical rationale may be requested. Compounded medications are not FDA-approved. No consumer self-ordering, no office stock, no bulk dispensing. Requests for hexarelin are reviewed before any preparation is made or released. Patient-specific pharmacy review keeps hexarelin requests attached to a prescriber, an identified patient, and a formulation decision rather than to a direct-to-consumer peptide protocol.
Pharmacist review
For hexarelin, the pharmacist review starts before any preparation is made. Valid patient-specific prescription required. Supporting clinical rationale may be requested. The pharmacist reviews ingredient status, sourcing, formulation feasibility, state requirements, patient-specific documentation, and whether dispensing is appropriate case by case.
Quality and traceability
If a hexarelin preparation is approved after pharmacy review, RonanRx applies source documentation, formulation records, lot traceability, release checks, and storage controls appropriate to the actual dosage form. Research-use vial storage practices do not substitute for pharmacy-assigned storage, beyond-use dating, sterility controls when applicable, or recallable batch records. The patient-specific framework and quality controls are documented in the cited compounding references 3534.
Cold chain
If a hexarelin preparation is approved after pharmacy review, RonanRx applies source documentation, formulation records, lot traceability, release checks, and storage controls appropriate to the actual dosage form. Research-use vial storage practices do not substitute for pharmacy-assigned storage, beyond-use dating, sterility controls when applicable, or recallable batch records.
FAQ
Frequently Asked Questions About Hexarelin
Can physicians request hexarelin through RonanRx?
Physicians may submit patient-specific prescription requests for pharmacy review. Certain preparations may be available now when clinically appropriate, lawfully prescribed, and approved by the dispensing pharmacy. Availability is determined case by case. Compounded medications are not FDA-approved, and no consumer self-ordering, office stock, or bulk dispensing is offered.3233
Is hexarelin FDA-approved?
No. Hexarelin was developed by Mediolanum Farmaceutici in Italy in the 1990s and studied in small phase 1 and phase 2 human trials, but it did not reach FDA approval for any indication. No manufactured hexarelin product is on the U.S 12. market.
How does hexarelin differ from ipamorelin?
Both bind the growth hormone secretagogue receptor GHS-R1a (the receptor for natural ghrelin) 21. Hexarelin also binds CD36, a scavenger receptor expressed on cardiomyocytes and macrophages, and produces dose-dependent rises in prolactin, ACTH, and cortisol that are smaller or absent with the selective GHS-R1a agonist ipamorelin. The CD36 interaction is the principal pharmacologic distinction between hexarelin (and other GHRP-family peptides) and ipamorelin 25.
Why was hexarelin not developed to FDA approval?
Phase 2 clinical development of hexarelin for growth hormone deficiency and for cardiac indications was not advanced to phase 3 in the late 1990s 12. The GH-axis diagnostic space subsequently moved to the GHRH-arginine test and to FDA-approved macimorelin (2017). Hexarelin remained available only as a research-grade peptide.
Is hexarelin allowed in competitive sport?
No. Hexarelin is prohibited at all times under section S2 of the World Anti-Doping Agency Prohibited List (Peptide Hormones, Growth Factors, Related Substances and Mimetics) 36. Routine anti-doping urine assays detect hexarelin and its metabolites 2830.
Clinician resource
Download the Hexarelin Clinical Monograph (PDF)
The full white paper covers every section on this page plus chemical identity, evidence grading, indication-by-indication summaries, research gaps, and reference appendix. Suitable for sharing with prescribing doctors and pharmacist reviewers.
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[ghigo1994] Ghigo E, Arvat E, Gianotti L, Imbimbo BP, Lenaerts V, Deghenghi R, Camanni F. Growth hormone-releasing activity of hexarelin, a new synthetic hexapeptide, after intravenous, subcutaneous, intranasal, and oral administration in man. Journal of Clinical Endocrinology and Metabolism. 1994. PMID 8126144. (accessed 2026-05-11)
[arvat1994] Arvat E, Gianotti L, Grottoli S, Imbimbo BP, Lenaerts V, Deghenghi R, Camanni F, Ghigo E. Arginine and growth hormone-releasing hormone restore the blunted growth hormone-releasing activity of hexarelin in elderly subjects. Journal of Clinical Endocrinology and Metabolism. 1994. PMID 7962341. (accessed 2026-05-11)
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[ciccarelli1996] Ciccarelli E, Grottoli S, Razzore P, Gianotti L, Arvat E, Deghenghi R, Camanni F, Ghigo E. Hexarelin, a synthetic growth hormone releasing peptide, stimulates prolactin secretion in acromegalic but not in hyperprolactinaemic patients. Clinical Endocrinology (Oxford). 1996. PMID 8706295. (accessed 2026-05-11)
[arvat1997] Arvat E, Gianotti L, Broglio F, Maccagno B, Bertagna A, Deghenghi R, Camanni F, Ghigo E. Oestrogen replacement does not restore the reduced GH-releasing activity of Hexarelin, a synthetic hexapeptide, in post-menopausal women. European Journal of Endocrinology. 1997. PMID 9186268. (accessed 2026-05-11)
[maghnie1998] Maghnie M, Spica-Russotto V, Cappa M, Autelli M, Tinelli C, Civolani P, Loche S, Severi F. The growth hormone response to hexarelin in patients with different hypothalamic-pituitary abnormalities. Journal of Clinical Endocrinology and Metabolism. 1998. PMID 9814463. (accessed 2026-05-11)
[arosio1998] Arosio M, Casati G, Biella O, Porretti S, Imbimbo BP, Faglia G. Lack of effect of hexarelin on TRH-induced TSH response in normal adult man. Journal of Endocrinological Investigation. 1998. PMID 9624598. (accessed 2026-05-11)
[howard1996] Howard AD, Feighner SD, Cully DF, Arena JP, Liberator PA, Rosenblum CI, Hamelin M, Hreniuk DL, Palyha OC, Anderson J, Paress PS, Diaz C, Chou M, Liu KK, McKee KK, Pong SS, Chaung LY, Elbrecht A, Dashkevicz M, Heavens R, Rigby M, Sirinathsinghji DJ, Dean DC, Melillo DG, Patchett AA, Nargund R, Griffin PR, DeMartino JA, Gupta SK, Schaeffer JM, Smith RG, Van der Ploeg LH. A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 1996. PMID 8688086. (accessed 2026-05-11)
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How to access
How to Access Hexarelin
Physicians may submit patient-specific prescription requests for Hexarelin for pharmacy review. Availability is determined case by case, and RonanRx is monitoring FDA's PCAC process and any subsequent agency action.
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