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Growth hormone axis

Hexarelin

Also known as Examorelin, Hexarelin acetate

Limited human data

Synthetic growth hormone-releasing peptide (GH secretagogue).

Not FDA-approved. Not on FDA's 503A category lists (May 14, 2026). Source, May 14, 2026

Identity. Hexarelin is a synthetic hexapeptide growth hormone-releasing peptide (GHRP) with the sequence His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2 (PMID 7957536). It is distinct from GHRP-6, GHRP-2, ipamorelin and MK-677. The alias Examorelin was not found in a primary pharmacology paper. Receptor-binding studies often use 125I-Tyr-Ala-hexarelin, an octapeptide analog. Do not attribute those results to the hexapeptide. The formulary vial is 2 mg (2,000 mcg), while studies dose in mcg/kg or flat mcg. Check mcg against mg before calculating.

At a glance

These dosages are a helpful guide, not a prescription. Every clinician is expected to do their own due diligence before prescribing.

  1. Start

    1.5 micrograms/kg subcutaneous, single dose1

    Human study

  2. Typical

    1.5 micrograms/kg subcutaneous twice daily (16-week study)2

    Human study

  3. Ceiling

    3 micrograms/kg subcutaneous, single dose (highest SC dose studied)1

    Human study
Frequency
Twice daily (longest studied regimen)2
Route
Subcutaneous1
Course
16 weeks (longest human study)2
Doses are per kg body weight and GH response was already attenuated at week 1 of twice-daily dosing; no label exists.
Calculate this dose

Dosing detail

Human studies

Human study

  • Healthy adult male volunteers, double-blind placebo-controlled rising-dose GH-release study

    0.5, 1 and 2 micrograms/kg (written as micrograms.kg-1 in abstract)3

    Route
    intravenous bolus
    Frequency
    single dose each
    Duration
    single administration
    n
    12
    Design
    Double-blind, placebo-controlled, rising-dose
    Source quote
    Twelve adult male volunteers received single intravenous boluses of 0.5, 1 and 2.micrograms.kg-1 hexarelin as well as placebo.

    Finding. GH rose dose-dependently, peaking about 30 min; the 2 micrograms/kg dose was close to maximal response (ED50 0.50 and 0.64 micrograms/kg).

  • Healthy young volunteers, GH response by route versus GHRH

    1.5 and 3 micrograms/kg1

    Route
    subcutaneous
    Frequency
    single dose
    Duration
    single administration
    n
    12
    Design
    Comparative single-dose study with IV saline and GHRH 1 microgram/kg as references
    Source quote
    We evaluated the GH-releasing activity of hexarelin, a new synthetic hexapeptide, after i.v. (1 and 2 micrograms/kg), sc (1.5 and 3 micrograms/kg), intranasal (20 micrograms/kg), and oral (po; 20 and 40 mg) administration to 12 healthy young volunteers.

    Finding. Dose-dependent GH response (AUC 3180 and 4459 micrograms.min.L). Bioavailability was 77.0% versus IV. 3 mcg/kg is the highest SC dose in the studies reviewed.

  • Healthy young volunteers, GH response by route versus GHRH

    1 and 2 micrograms/kg1

    Route
    intravenous
    Frequency
    single dose
    Duration
    single administration
    n
    12
    Design
    Comparative single-dose study with IV saline and GHRH 1 microgram/kg as references
    Source quote
    We evaluated the GH-releasing activity of hexarelin, a new synthetic hexapeptide, after i.v. (1 and 2 micrograms/kg), sc (1.5 and 3 micrograms/kg), intranasal (20 micrograms/kg), and oral (po; 20 and 40 mg) administration to 12 healthy young volunteers.

    Finding. At 1 mcg/kg, GH AUC was about 2x that of GHRH 1 mcg/kg. 2 mcg/kg gave a further increase.

  • Healthy young volunteers, GH response by route versus GHRH

    20 micrograms/kg1

    Route
    intranasal
    Frequency
    single dose
    Duration
    single administration
    n
    12
    Design
    Comparative single-dose study with IV saline and GHRH 1 microgram/kg as references
    Source quote
    We evaluated the GH-releasing activity of hexarelin, a new synthetic hexapeptide, after i.v. (1 and 2 micrograms/kg), sc (1.5 and 3 micrograms/kg), intranasal (20 micrograms/kg), and oral (po; 20 and 40 mg) administration to 12 healthy young volunteers.

    Finding. Bioavailability was 4.8%. This is not a transferable SC dose, and the route is not used with the formulary vial.

  • Healthy young volunteers, GH response by route versus GHRH

    20 and 40 mg total (not mcg)1

    Route
    oral
    Frequency
    single dose
    Duration
    single administration
    n
    12
    Design
    Comparative single-dose study with IV saline and GHRH 1 microgram/kg as references
    Source quote
    We evaluated the GH-releasing activity of hexarelin, a new synthetic hexapeptide, after i.v. (1 and 2 micrograms/kg), sc (1.5 and 3 micrograms/kg), intranasal (20 micrograms/kg), and oral (po; 20 and 40 mg) administration to 12 healthy young volunteers.

    Finding. Bioavailability was 0.3%. This is not a transferable SC dose, and the route is not used with the formulary vial. 20 mg = 20,000 mcg.

  • Healthy older adults, 16-week chronic dosing; GH response to a single hexarelin injection measured at weeks 0, 1, 4, 16 and 20

    1.5 micrograms/kg BW (written as 'micrograms/kg BW' in abstract)2

    Route
    subcutaneous
    Frequency
    twice daily
    Duration
    16 weeks
    n
    Not stated in this abstract; 12 healthy elderly per the companion report (PMID 10990150)
    Design
    Clinical trial with repeated GH-response testing (PubMed type: Clinical Trial). The abstract does not state a control arm. Population: healthy older adults, who respond less to hexarelin than young adults (PMID 9801989: peak GH 22.4 vs 60.9 micrograms/l).
    Source quote
    We have, therefore, assessed the effects of 16 weeks of twice-daily s.c. hexarelin therapy (1.5 micrograms/kg BW) on the GH response to a single injection of hexarelin, and also the GH response to hexarelin 4 weeks after cessation of hexarelin therapy.

    Finding. GH AUC to a test injection fell from 19.1 (week 0) to 13.1 (week 1), 12.3 (week 4) and 10.5 (week 16) micrograms/L.h. It returned to 19.4 four weeks after stopping. IGF-I and IGFBP-3 were unchanged. The authors judged the biological impact on the GH-IGF-I axis minimal.

  • Companion report of the same 16-week study: attenuation of GH response

    Not stated in this abstract not stated4

    Route
    subcutaneous
    Frequency
    twice daily
    Duration
    16 weeks
    n
    12 healthy elderly
    Design
    Clinical trial, repeated GH-response testing
    Source quote
    The effect of twice-daily subcutaneous injections of hexarelin on GH release was therefore investigated over a period of 16 weeks in 12 healthy elderly individuals.

    Finding. The authors conclude that the attenuation of GH response after long-term hexarelin is partial and reversible.

  • Same chronic regimen; pituitary-adrenal axis and prolactin

    1.5 micrograms/kg body weight5

    Route
    subcutaneous
    Frequency
    twice daily
    Duration
    16 weeks
    n
    Not stated in this abstract
    Design
    Clinical trial, ACTH/cortisol/PRL responses at baseline, 16 and 20 weeks
    Source quote
    Each subject received twice-daily subcutaneous hexarelin therapy (1.5 micrograms/kg body weight) for 16 weeks.

    Finding. Cortisol AUC fell at week 16 and recovered by week 20. Urinary free cortisol and prolactin AUC did not change.

  • Healthy young men, 24-hour intermittent dosing

    1.5 microg/kg (as written in abstract)6

    Route
    subcutaneous
    Frequency
    two or three times daily
    Duration
    24 hours, with an IV hexarelin 1 microg/kg challenge at the end
    n
    6
    Design
    Randomized controlled trial (per PubMed type), 24-h sampling every 20 min
    Source quote
    We investigated the impact of two or three times daily s.c. administration of a short-acting peptidyl GHS, the hexapeptide HEX (1.5 microg/kg) on 24-h GH, PRL, ACTH and cortisol secretion (sampling every 20 min) in six normal young men.

    Finding. Two and three daily injections raised 24-h GH equally. Prior dosing blunted the GH response and abolished the ACTH and cortisol response to the IV challenge.

  • Patients with possible pituitary disease; diagnostic GH-reserve test versus insulin tolerance test

    2 microg/kg (as written in abstract)7

    Route
    not stated in abstract
    Frequency
    single test dose
    Duration
    single administration
    n
    19
    Design
    Within-patient comparison with insulin-induced hypoglycaemia
    Source quote
    The changes in GH and cortisol in response to insulin-induced hypoglycaemia (intravenous human Actrapid 0.15 IU/kg) and hexarelin (2 microg/kg) in 19 patients with possible pituitary disease (5 males, mean age 39 years, range 21-70) were compared.

    Finding. Peak GH was higher after hexarelin than after hypoglycaemia. Hexarelin was not useful as a test of ACTH/cortisol reserve.

  • Children and adults, GH response to the maximal effective dose versus GHRH and GHRH plus arginine

    2 micrograms/kg8

    Route
    intravenous
    Frequency
    single test dose
    Duration
    single administration
    n
    36 (6 prepubertal, 6 pubertal, 12 young adults, 12 elderly)
    Design
    Comparative single-dose study
    Source quote
    We compared the GH response to the maximal effective dose of Hexarelin (2 micrograms/kg i.v.), an hexapeptide belonging to GHRP family, with that of GHRH (1 microgram/kg i.v.) alone and combined with arginine (ARG, 0.5 g/kg i.v.)

    Finding. A powerful GH stimulus in pubertal children and young adults only. The response was weaker in elderly subjects (peak 22.4 versus 60.9 micrograms/l).

  • Patients with dilated (n=8) or ischemic (n=5) cardiomyopathy vs normal and GH-deficient controls; acute LVEF effect

    Not stated in abstract not stated9

    Route
    intravenous
    Frequency
    acute administration
    Duration
    acute
    n
    13 patients (8 dCMP, 5 iCMP) plus 14 controls
    Design
    Comparative study
    Source quote
    Acute hexarelin administration increases LVEF in iCMP patients (as in normals and GHD) but not in dCMP patients in spite of a similar GH releasing effect and basal LVEF.

    Finding. LVEF rose in ischemic cardiomyopathy (peak 26.2%, P<0.05) but not in dilated cardiomyopathy. This shows GH-independent cardiac activity. It gives no evidence on the benefit or safety of chronic SC use.

Clinical practice

Clinical practice

This is not clinician dosing. The cited review states that its table values are self-reported online practice and 'MUST NOT be interpreted as clinically validated, regulatory-approved, or safe for use.' No compounding-pharmacy or prescriber protocol was found. The vendor figures should be checked against the live vendor pages before display. Show only SC rows in any dosing table. IV, intranasal and oral study doses must not be displayed as SC dosing.

Start
Not sourced. No clinician, compounding-pharmacy or professional-education start dose was found.
Titration
Not sourced.
Typical
100-200 micrograms per SC injection, from self-reported online (bodybuilding forum) patterns summarized in a peer-reviewed review. One vendor page states about 100 mcg per injection.
Ceiling
No maximum has been established, and this is not a safety ceiling. The highest SC dose studied in humans was 3 mcg/kg as a single dose (PMID 8126144). The highest IV dose studied was 2 mcg/kg, which gave a near-maximal GH response (PMID 7957536). Flat 100-200 mcg doses exceed 3 mcg/kg in patients under about 67 kg (at 50 kg, 200 mcg = 4 mcg/kg, above any studied SC dose). Conversion at 70 kg: 1.5 mcg/kg = about 105 mcg; 3 mcg/kg = about 210 mcg.
Frequency
Self-reported practice: 1-2 injections per day (review of online forum patterns). Vendor pages disagree (1-3 times daily on one, 2-3 times daily on another). In human data, twice daily SC for 16 weeks was the longest regimen (PMID 9589671). Three times daily was studied for 24 hours only (PMID 11888836, n=6). Frequencies above twice daily have no chronic human data.
Route
Subcutaneous
Timing
On an empty stomach (vendor page). No clinician source.
Cycle
Self-reported practice: 8-12 weeks on, 4 weeks off. Not supported by controlled data. In the only chronic human study (twice daily 1.5 mcg/kg, 16 weeks, PMID 9589671), GH response to a test injection was already lower at week 1 (19.1 to 13.1 micrograms/L.h) and significantly lower by week 4. It recovered 4 weeks after stopping.

Sources

  • Clinical practicePeer-reviewed review10
    Bodybuilding-related forums: 100-200 µg SC 1–2 injections/day; typical cycle: 8–12 weeks on, followed by 4 weeks off

What clinics and vendors publish

These ranges come from clinic and vendor publications, not studies.

Community-reported
  • Community-reportedVendor page11
    ~100 mcg per injection in practice
  • Community-reportedVendor page12
    100-200 mcg per injection

Safety

Serious warnings

  • No FDA label exists, so no formal boxed warning or contraindication has been established. Absence of a label is not evidence that no risks exist.13
  • No long-term safety data exist. The longest human exposure was 16 weeks (n=12 healthy elderly). The trials were physiology studies, not safety trials.10

Contraindications

  • Cautions based on clinical judgment, not label contraindications. Use caution in known or suspected Cushing disease or hypercortisolism (GH secretagogues cause an exaggerated ACTH/cortisol response in Cushing disease, PMID 11322506). Use caution in hyperprolactinaemia or prolactinoma (prolactin-releasing activity). Use caution in significant cardiovascular disease (GHS-R activity in the heart; acute LVEF effects, PMID 11959048). Use caution in diabetes or dysglycaemia (a class effect noted in a review). Use caution in active or recent malignancy (a theoretical IGF-1 mitogenic concern, with no direct clinical evidence). Pregnancy and lactation: no human data were located. Hexarelin is not stated to be contraindicated, so prescriber judgment is required.14

Adverse effects

  • Class-level review: reported adverse effects of GH-axis performance peptides include endocrine and metabolic disturbances (prolactin and cortisol elevations, appetite changes, dysglycaemia), fluid retention, myalgia/arthralgia and injection-site reactions. These are not specific to hexarelin.10
  • Hexarelin-specific: in human studies it activates prolactin release and the corticotropic axis, raising ACTH and cortisol.10
  • Trial-reported: IV hexarelin (1 microg/kg) raised GH, PRL, ACTH and cortisol in six healthy young men. Prior intermittent dosing blunted GH and abolished the ACTH and cortisol rise.6
  • Trial-reported: over 16 weeks of twice-daily 1.5 micrograms/kg SC, the authors concluded that over-stimulation of the pituitary-adrenal axis and prolactin did not occur. The cortisol response fell.5
  • Review table (2026): 'Generally well tolerated with no serious adverse events reported.' It also lists reduced slow-wave sleep, a theoretical mitogenic concern via IGF-1 with no direct evidence of carcinogenesis in clinical studies, and no long-term safety data. Quantitative adverse-event rates were not reported in the abstracts reviewed. The primary sleep study was not located.10
  • Cardiotropic: acute IV hexarelin raised LVEF in ischemic cardiomyopathy but not in dilated cardiomyopathy (PMID 11959048). This shows cardiovascular activity, not clinical benefit or chronic safety.9
  • Chronic SC dosing attenuated the GH response from week 1 (partial and reversible), and IGF-I did not rise. The efficacy of long-term use is unproven.2

Monitoring

  • Review guidance for suspected exposure: for mild hypercortisolemia, consider the GHRP class effect and retest after washout. For mild hyperprolactinaemia, repeat off-cycle before pituitary imaging.10
  • Practice-level suggestion based on the effects above, not a published guideline: baseline and periodic IGF-1, fasting glucose or HbA1c, prolactin and morning cortisol; blood pressure and heart rate; symptom review for sleep disturbance, fluid retention and arthralgia. Do not assume IGF-1 will rise (it did not in the 16-week study).2

Interactions

  • A vendor page advises close monitoring in patients on insulin because GH affects blood sugar. No primary interaction study was found.11

Handling

Reconstitution

A vendor page names bacteriostatic water for multi-use vials. No volume or concentration is given for the 2 mg formulary vial. Follow the dispensing pharmacy's instructions.

Storage before mixing

Beyond a vendor note (refrigerate short term, freeze for storage over 2 months), no source is available. Defer to pharmacy labeling.

Storage after mixing

Vendor page: do not freeze reconstituted solution; use within 28-30 days. This comes from the vendor page only. Defer to the pharmacy beyond-use date.11

Evidence

Human evidence is limited to small physiology studies in healthy volunteers and a few patient groups. These include single-dose IV, SC, intranasal and oral GH-release studies, and a 16-week SC study in 12 healthy elderly adults that showed a partial, reversible loss of GH response. There are no clinical-outcome trials and no FDA-approved product. Practice dosing rests on self-reported online and vendor protocols. The longest human exposure was 16 weeks (n=12, healthy older adults). No long-term safety data exist.

Mechanism

Hexarelin stimulates GH release in vitro and in vivo. In humans, GH rises dose-dependently after injection, peaking at about 30 min, with an IV half-life of about 55 min (PMID 7957536). It also acutely raises prolactin, ACTH and cortisol. GH secretagogues act on the ghrelin/GH secretagogue receptor GHS-R1a, which is also present in cardiovascular tissue (PMID 16309920, a review of ghrelin and synthetic secretagogues in general, not specific to hexarelin).31015

Availability

Amounts offered

  • 2 mg

Custom strengths on request.

References

According to PubMed

  1. 1Growth hormone-releasing activity of hexarelin, a new synthetic hexapeptide, after intravenous, subcutaneous, intranasal, and oral administration in man.J Clin Endocrinol Metab, 1994
  2. 2Growth hormone status during long-term hexarelin therapy.J Clin Endocrinol Metab, 1998
  3. 3Growth hormone-releasing activity of hexarelin in humans. A dose-response study.Eur J Clin Pharmacol, 1994
  4. 4Does desensitization to hexarelin occur?Growth Horm IGF Res, 1998
  5. 5The effect of chronic hexarelin administration on the pituitary-adrenal axis and prolactin.Clin Endocrinol (Oxf), 1999
  6. 6Impact 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.Eur J Endocrinol, 2002
  7. 7Hexarelin as a test of pituitary reserve in patients with pituitary disease.Clin Endocrinol (Oxf), 1999
  8. 8Hexarelin, a synthetic GH-releasing peptide, is a powerful stimulus of GH secretion in pubertal children and in adults but not in prepubertal children and in elderly subjects.J Endocrinol Invest, 1998
  9. 9GH-independent cardiotropic activities of hexarelin in patients with severe left ventricular dysfunction due to dilated and ischemic cardiomyopathy.Eur J Heart Fail, 2002
  10. 10The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration.Front Endocrinol (Lausanne), 2026
  11. 11Hexarelin Injection Dosage & ProtocolPeptide Initiative (vendor/educational site, not a clinic), 2026
  12. 12Hexarelin Dosing Protocols and Administration | Peptide Protocol WikiPeptide Protocol Wiki (commercial-adjacent educational site), 2026
  13. 13Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act (content current as of 05/14/2026)FDA, 2026
  14. 14Biologic activities of growth hormone secretagogues in humans.Endocrine, 2001
  15. 15Effects of ghrelin and synthetic GH secretagogues on the cardiovascular system.Trends Endocrinol Metab, 2005
  16. 16Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (Category 2; content current as of 04/22/2026)FDA, 2026

Last reviewed 2026-10-14. 47 figures checked against their sources. How this works