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Hexarelin

Hexarelin (His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2) is a synthetic hexapeptide growth hormone secretagogue (a growth hormone-releasing peptide, GHRP) that binds the growth hormone secretagogue receptor (GHS-R1a, the ghrelin receptor) and stimulates pulsatile GH release from the pituitary. Its GH-releasing potency in humans is well documented in small, short-term studies, but it is an unapproved research peptide with no long-term human safety or efficacy data for the physique, anti-aging, or performance uses for which it is taken. The main risks are that it is not GH-selective, also raising ACTH, cortisol and prolactin to a degree comparable to CRH/AVP, and, as a class effect of GH secretagogues, reducing insulin sensitivity and potentially raising blood glucose. It produces an acute cardiac inotropic effect and binds cardiac CD36, which in diseased/atherosclerotic vessels mediates coronary vasoconstriction in animal models. GH/IGF-1 elevation and demonstrated in-vitro cardiomyocyte proliferation raise theoretical concern in anyone with cancer or cardiovascular disease. Repeated dosing causes desensitization. Because the human evidence is limited to acute surrogate-endpoint studies, certainty about real-world safety is low; use should be supervised by a physician with bloodwork.

Clinical readoutPeptide · gh-secretagogue
Hepatic strainNone
CardiovascularNone
HPTA suppressionNone
Half-life
55 min
Route
Studied via intravenous…
Evidence
C
Active
Plasma GH rises within…
55 min1.8 h2.8 h3.7 h4.6 h
Illustrative single-compartment washout · each mark = one half-life · t½ ≈ Approximately 55 minutes after intravenous bolus in healthy adults (single-dose study).
Pharmacology

Mechanism of action

Hexarelin is a synthetic GHRP that acts on the growth hormone secretagogue receptor (GHS-R1a) at both pituitary and hypothalamic levels to stimulate GH secretion. It is thought to work by functionally antagonizing somatostatin tone and by enhancing endogenous GHRH-secreting neuron activity, which is why its GH response is synergistic with GHRH and largely resistant to inhibitory influences that abolish the GHRH response. Its effect is not GH-selective: it also stimulates ACTH/cortisol (via central mechanisms overlapping with vasopressin/CRH) and prolactin release. Beyond the pituitary, hexarelin binds a distinct cardiac receptor, the scavenger glycoprotein CD36, expressed on cardiomyocytes and microvascular endothelium, which mediates GH-independent cardiovascular actions.
Kinetics

Pharmacokinetics

Half-life

Approximately 55 minutes after intravenous bolus in healthy adults (single-dose study).

Active duration

Plasma GH rises within minutes, peaks around 30 minutes, and returns to baseline within about 180-240 minutes after a single dose.

Route

Studied via intravenous and subcutaneous injection; also active intranasally and orally, though oral bioavailability is low. For monitoring/washout planning, not evasion.

Metabolism & clearance

As a small peptide it is presumed to be cleared by enzymatic (peptidase) hydrolysis with partial renal elimination; detailed human metabolism/clearance data are not well characterized. This information is provided for washout and monitoring, not to guide test evasion.

For monitoring and washout planning, not drug-test evasion.

Reported effects

Physiological & performance effects

  • Dose-dependent, reproducible acute rise in serum GH after single doses (0.5-2 micrograms/kg IV), with a near-maximal response around 2 micrograms/kg
  • GH-releasing potency greater than GHRH 1-29 at comparable doses in human studies
  • Concurrent (non-selective) increases in ACTH, cortisol and prolactin
  • Acute, short-lasting positive inotropic effect (increased left ventricular ejection fraction) in healthy men, appearing GH-independent
  • Modest acute increase in appetite reported during HPA-axis testing
  • Alteration of sleep architecture: reduced slow-wave (stage 4) sleep with increased nocturnal GH, ACTH, cortisol and prolactin
  • With repeated/continuous administration, partial desensitization (tachyphylaxis) of the GH and ACTH/cortisol responses
  • No proven long-term benefit for body composition, muscle strength, or anti-aging outcomes in humans
Safety

Adverse effects by system

Cardiovascular

Acute administration produces a short-lasting positive inotropic effect (increased LVEF) without significant change in blood pressure or heart rate in healthy men; transient facial flushing is common. Hexarelin binds cardiac CD36, which in animal hearts mediates dose-dependent coronary vasoconstriction, most pronounced in hypercholesterolemic/atherosclerotic and hypertensive vessels (preclinical). Long-term human cardiovascular safety is unknown.

Hepatic

No human hepatotoxicity data. As a peptide it is not a known direct hepatotoxin; sustained GH/IGF-1 elevation with chronic use is a theoretical, unquantified concern. Evidence is inadequate.

Endocrine / HPTA

Not GH-selective: raises ACTH, cortisol and prolactin comparably to CRH/vasopressin. As a GH-secretagogue class effect, decreases insulin sensitivity and can raise blood glucose. Chronic use raises IGF-1 and causes desensitization of GH and ACTH/cortisol responses. It does not directly act on the gonadal (testosterone) axis.

Reproductive

No human fertility, pregnancy, or lactation data. Modest prolactin elevation could theoretically affect libido or menstrual function if sustained, but this has not been demonstrated. Not documented to be directly gonadotoxic.

Neuropsychiatric

No formal psychiatric adverse-event data. Documented effects on appetite (acute increase) and sleep (reduced slow-wave sleep), which could plausibly affect mood/daytime function, but this has not been studied.

Renal

No human renal toxicity data. Peptide is presumed partly renally cleared; effects in renal impairment are uncharacterized.

Hematologic

No known hematologic effects and no dedicated hematologic safety data; leptin, TNF-alpha and soluble TNF receptors were unchanged in a sleep-endocrine study, suggesting no acute immune/inflammatory signal.

Dermatologic

Transient facial flushing and a sensation of warmth are the most commonly reported acute effects; sweating is described with GHRPs generally.

Recovery

HPTA suppression & recovery

Suppression: Not a direct HPTA (gonadal-axis) suppressant; primary endocrine risks are HPA-axis activation (ACTH/cortisol), prolactin elevation, and reduced insulin sensitivity

Unlike anabolic-androgenic steroids, hexarelin is a GH secretagogue and is not documented to suppress the hypothalamic-pituitary-gonadal (testosterone) axis, so post-cycle SERM therapy is not an established indication here. If gonadal or reproductive symptoms (e.g., low libido, menstrual change, galactorrhea from prolactin elevation) or HPA-axis concerns arise, evaluation and any pharmacologic management (single-agent only, if ever indicated) should be directed by an endocrinologist rather than self-managed. Defer all recovery decisions to a qualified clinician.

Bloodwork & vitals

Monitoring

Recommended labs & checks
IGF-1 (baseline and periodic, given GH-axis stimulation)Fasting glucose and HbA1c (GH-secretagogue class reduces insulin sensitivity)Fasting insulin / insulin sensitivity assessmentMorning cortisol and ACTH (HPA-axis activation)ProlactinLipid panelECG and, if cardiac concern, echocardiography

Cadence: Baseline before any use, then periodic (e.g., every few months) while used and if symptoms develop; all interpretation by a clinician.

Warning signs — seek care
  • Chest pain, palpitations, or exertional breathlessness
  • New or worsening edema
  • Persistent hyperglycemia symptoms (excess thirst, polyuria, blurred vision)
  • Carpal tunnel-type symptoms or joint swelling (GH/IGF-1 excess)
  • Galactorrhea or menstrual changes (prolactin)
  • Severe headache or visual disturbance
  • Any new cardiovascular symptom in someone with known heart disease
Do not use if

Contraindications

  • Active or prior malignancy (GH/IGF-1 are mitogenic; hexarelin stimulated cardiomyocyte proliferation in vitro) - avoid without oncology guidance
  • Diabetes mellitus or impaired glucose tolerance (GH secretagogues reduce insulin sensitivity and can raise blood glucose)
  • Known coronary artery disease, hypercholesterolemia, or significant atherosclerosis (theoretical CD36-mediated coronary vasoconstriction in diseased vessels)
  • Cushing's syndrome or other hypercortisolism (hexarelin raises ACTH/cortisol)
  • Hyperprolactinemia or prolactin-sensitive conditions
  • Pregnancy and breastfeeding (no safety data)
  • Children/adolescents outside supervised endocrinology care
  • Use without physician oversight and baseline bloodwork
Combinations

Interaction profile

  • MajorWith insulin: Metabolic / glucose
  • ModerateWith another GH secretagogue: Metabolic / glucose
  • ModerateWith growth hormone: Metabolic / glucose
  • ModerateWith IGF-1: Metabolic / glucose
  • ModerateWith a GLP-1 / incretin agonist: Metabolic / glucose
  • ContraindicatedWith DNP: Additive cardiovascular strain

Check a specific combination in the interaction checker.

Harm reduction

Reducing harm & when to stop

  • Hexarelin is an unapproved research peptide with no long-term human safety or efficacy data for physique, performance, or anti-aging use - treat any use as experimental and inherently uncertain.
  • Do not use if you have a personal or family history of cancer, active cardiovascular disease, diabetes/prediabetes, Cushing's syndrome, or hyperprolactinemia without a physician's evaluation.
  • Because it raises cortisol, ACTH, prolactin and blood glucose and is not GH-selective, obtain baseline bloodwork (glucose/HbA1c, IGF-1, cortisol, prolactin, lipids) and repeat periodically under clinician supervision.
  • Stop and seek medical care for chest pain, palpitations, breathlessness, new swelling/edema, severe headache or visual changes, galactorrhea, or persistent high-blood-sugar symptoms.
  • Do not combine with other GH-axis drugs, or self-manage any perceived hormonal disruption; direct endocrine questions to an endocrinologist.
  • Repeated dosing causes desensitization; escalating dose to chase an effect increases risk without established benefit.
  • This monograph is for risk awareness and is not an endorsement, dosing recommendation, or guidance on obtaining the substance.
Evidence

Citations (16)

Every clinical claim above is tied to a primary source. Overall evidence grade C — graded to the best available evidence for its core claims.

  1. 01

    Hexarelin is a synthetic hexapeptide GHRP (His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2) that dose-dependently raises GH after single IV doses (0.5-2 micrograms/kg), peaking ~30 min and returning to baseline within 180-240 min, with a half-life of about 55 minutes.

    RCTGrowth hormone-releasing activity of hexarelin in humans. A dose-response study.PMID 7957536 ↗

  2. 02

    GHRPs including hexarelin act on GHS receptors at pituitary and hypothalamic levels, likely by antagonizing somatostatin and enhancing GHRH activity; they are synergistic with GHRH and show partial desensitization with prolonged administration.

    ReviewGrowth hormone-releasing peptides.PMID 9186261 ↗

  3. 03

    Hexarelin's GH-releasing activity is greater than GHRH 1-29 at 1 microgram/kg IV in humans.

    RCTPMID 9364340 ↗

  4. 04

    GH secretagogues are not GH-selective and have prolactin- and ACTH/cortisol-releasing activity as well as cardiovascular and appetite/sleep effects.

    ReviewPMID 11322506 ↗

  5. 05

    Hexarelin significantly increases GH, prolactin, ACTH and cortisol in humans, with GH and ACTH responses varying by age while prolactin and cortisol responses do not.

    CohortPMID 9437229 ↗

  6. 06

    Hexarelin and GHRP-2 raise GH, and also raise prolactin, ACTH and cortisol; flushing was noted among effects.

    RCTPMID 9285939 ↗

  7. 07

    Hexarelin stimulates the HPA axis (ACTH/cortisol) at least in part via arginine vasopressin, and caused a small acute increase in appetite in healthy men.

    RCTPMID 10404825 ↗

  8. 08

    Hexarelin's ACTH/cortisol-releasing activity in humans overlaps with that of vasopressin and is similar to CRH.

    RCTHexarelin, a synthetic growth-hormone releasing peptide, shows no interaction with corticotropin-releasing hormone and vasopressin on adrenocorticotropin and cortisol secretion in humans.PMID 9430449 ↗

  9. 09

    Repeated daily subcutaneous hexarelin augmented 24-h GH secretion but a subsequent IV challenge showed blunted GH and abolished ACTH/cortisol responses (desensitization); IGF-1 was unchanged over the 1-day schedules.

    RCTImpact of two or three daily subcutaneous injections of hexarelin, a synthetic growth hormone (GH) secretagogue, on 24-h GH, prolactin, adrenocorticotropin and cortisol secretion in humans.PMID 11888836 ↗

  10. 10

    Acute hexarelin produced a short-lasting positive inotropic effect (increased LVEF) in healthy men without significant change in blood pressure or heart rate; it raised cortisol and caused flushing; the inotropic effect appeared GH-independent.

    RCTAcute cardiovascular and hormonal effects of GH and hexarelin, a synthetic GH-releasing peptide, in humans.PMID 10342360 ↗

  11. 11

    Hexarelin binds cardiac CD36, and CD36 activation mediates dose-dependent coronary vasoconstriction in perfused hearts, accentuated in hypercholesterolemic/hypertensive (CD36-relevant) models.

    PreclinicalPMID 11988484 ↗

  12. 12

    Hexarelin has direct GH-independent cardiovascular actions mediated by CD36, reviewed as a potential cardioprotective but also vasoactive agent.

    ReviewPMID 25278975 ↗

  13. 13

    Hexarelin (and ghrelin) stimulate H9c2 cardiomyocyte proliferation in vitro, supporting peripheral cardiac effects independent of GH secretion.

    PreclinicalPMID 12379504 ↗

  14. 14

    GH secretagogues are generally well tolerated in short-term studies but decrease insulin sensitivity and can raise blood glucose; long-term safety including cancer and mortality outcomes is not established.

    ReviewThe Safety and Efficacy of Growth Hormone Secretagogues.PMID 28400207 ↗

  15. 15

    Hexarelin reduced slow-wave (stage 4) sleep while increasing nocturnal GH, ACTH, cortisol and prolactin; leptin, TNF-alpha and soluble TNF receptors were unchanged.

    RCTHexarelin decreases slow-wave sleep and stimulates the secretion of GH, ACTH, cortisol and prolactin during sleep in healthy volunteers.PMID 15177700 ↗

  16. 16

    GH secretagogue signaling (ghrelin/hexarelin) intersects with glucose/insulin and PPAR-gamma metabolism, relevant to diabetes and diabetic heart disease.

    ReviewPMID 25645463 ↗

Last reviewed 2026-07-06 · Verified against PubMed · Educational, not medical advice