Hexarelin
A potent 1990s growth hormone releaser that also raised cortisol and prolactin, briefly lifted heart pumping, and lost part of its effect over months of use
Hexarelin is GHRP-6 with one methyl group added: six amino acids that switch on the ghrelin receptor and release growth hormone. In small 1990s studies it released more growth hormone than GHRH, nudged cortisol and prolactin up, and briefly raised the heart's ejection fraction. After 16 weeks of twice-daily injections its growth hormone effect was about 45% smaller, and IGF-1 had not risen. It was never approved; examorelin is its official nonproprietary name.
What is it?
Hexarelin is a synthetic hexapeptide from the growth hormone-releasing peptide family: GHRP-6 with a methyl group added to its D-tryptophan, a change its developers made because 2-methyl-tryptophan is chemically more stable. It acts on the ghrelin receptor, which growth hormone secretagogues use at the pituitary, the hypothalamus and, the heart studies suggest, the heart. Examorelin is its international nonproprietary name, and PubChem files both names under one record.
In people it is a fast, strong growth hormone releaser. In 12 healthy men a 2 µg/kg dose into a vein raised growth hormone to a mean peak of 55 ng/mL about 30 minutes later, close to the maximum response, and in short children it released more than GHRH did. It is not selective. Cortisol and prolactin rose after single doses in several studies, though less than after ghrelin itself, and four doses given through the evening cut deep sleep in seven healthy men.
The heart findings are what keep it in the literature. In two small studies a single dose raised the left ventricular ejection fraction by about seven percentage points within 15 to 30 minutes, including in seven men with growth hormone deficiency whose growth hormone barely moved, which points to an effect that does not run through growth hormone. A 2014 review credits CD36, a receptor on heart cells, with the protective effects seen in animals, where hexarelin preserved heart function after induced heart attacks in mice.
What limits it is repetition. Sixteen weeks of twice-daily injections left the growth hormone response to a test dose about 45% smaller, back to normal four weeks after stopping, with no change in IGF-1, body fat, lean mass or bone density; in beagles given high doses the response rose, then fell below where it started by week six. Hexarelin was never approved anywhere, and it is not among the substances FDA lists for 503A compounding, under evaluation or flagged for safety risks.
Mechanism of Action
Hexarelin works through two receptors. The ghrelin receptor explains the growth hormone and the extra hormones, and that pathway is established in people. The CD36 pathway is the basis of the heart research; it rests on animal work and on two small human studies that measured the heart's pumping for an hour.
Ghrelin receptor: growth hormone
Hexarelin releases growth hormone within 15 to 30 minutes, more than GHRH at the doses tested. With GHRH it is synergistic: in six healthy men the two together released more than the sum of each alone, a boost that disappeared when both were repeated an hour or two later. Growth hormone secretagogue receptors sit in the pituitary and the hypothalamus.
Cortisol, ACTH and prolactin
Single doses also raise ACTH, cortisol and prolactin, less than ghrelin does. The rise is striking in Cushing's disease, which is why hexarelin was tried as a diagnostic test. Repetition dulls it rather than building it up: after 16 weeks of use the cortisol response was lower than at the start, and prolactin was unchanged.
CD36 and the heart
One dose into a vein raised the ejection fraction of healthy men and of men with growth hormone deficiency, without changing blood pressure, heart rate or catecholamines, while growth hormone given directly at a matching level did nothing. A 2014 review names CD36, a scavenger receptor, as a specific cardiac receptor for hexarelin that mediates its protective effects in animals.
Desensitisation
Repeated exposure blunts the response. A second dose two hours after the first produced a lower peak. After a day of two or three injections, a further dose gave a smaller growth hormone rise and no ACTH or cortisol rise. After 16 weeks of twice-daily use the response was about 45% smaller, and it recovered within four weeks of stopping.
Published Research
Our evidence set holds 54 papers that name hexarelin, and 39 name it in their titles, which is what a study card needs. Four were added by hand because the search ranked them below its cut: the first human dose-response study, the two animal studies that measured hexarelin's own half-life, and a 24-hour dosing study. The 17 cards below are 11 human studies, one review and five animal studies. The human studies are all small, the largest 60 children and most 6 to 16 adults, and none tested a clinical benefit; the longest ran 16 weeks and found no change in body composition or bone density.
Dose-response in 12 healthy men
In a double-blind, placebo-controlled rising-dose study, 12 healthy men received single intravenous doses of 0.5, 1 and 2 µg/kg. Growth hormone peaked about 30 minutes later at mean levels of 26.9, 52.3 and 55.0 ng/mL, against 3.9 ng/mL on placebo, then fell with a half-life of about 55 minutes, back to baseline within four hours. The estimated half-maximal dose was 0.5 to 0.64 µg/kg, so 2 µg/kg was close to the maximum response.
Children: stronger than GHRH
Given 2 µg/kg into a vein, hexarelin raised growth hormone promptly in all 45 short but otherwise normal children, peaking at 15 to 30 minutes and exceeding the response to GHRH; testosterone priming raised it further in five boys. Ten obese children responded less, and five people with organic hypopituitarism did not respond at all. Cortisol and prolactin rose slightly and returned to baseline within two hours, and no participant reported side effects.
Synergy with GHRH, and repeat doses
Six healthy men received intravenous hexarelin (1 µg/kg), GHRH or both, with a second bolus 60 or 120 minutes later. Hexarelin's first dose produced a higher peak of growth hormone secretion than GHRH's, and the two together released more than the sum of each. A second hexarelin dose at 120 minutes produced a lower peak, and the synergy with GHRH was lost when the doses were repeated.
16 weeks: a partial, reversible fade
Adults injected 1.5 µg/kg under the skin twice daily for 16 weeks. The growth hormone response to a test dose, measured as area under the curve, fell from 19.1 µg/L·h at baseline to 12.3 at week 4 and 10.5 at week 16, then recovered to 19.4 four weeks after stopping. IGF-1, IGFBP-3, body fat, lean mass and bone density did not change; of the bone markers measured, only one formation marker rose.
16 weeks: cortisol and prolactin
On the same twice-daily regimen, the cortisol response to the morning injection shrank from 1,506 to 1,222 nmol/L·h over 16 weeks and returned to 1,586 four weeks after stopping. ACTH and prolactin responses, basal cortisol, 24-hour urinary cortisol and cortisol-binding globulin did not change. The authors conclude that this regimen did not overstimulate the adrenal axis or prolactin.
A day of two or three injections
Six young men injected 1.5 µg/kg under the skin two or three times in a day, with blood drawn every 20 minutes for 24 hours. Both schedules raised 24-hour growth hormone equally, by enlarging each pulse rather than adding pulses, while IGF-1, prolactin, ACTH and cortisol did not change. A test dose into a vein at the end then produced a blunted growth hormone rise and no ACTH or cortisol response.
Heart pumping in GH-deficient men
Seven men with growth hormone deficiency and nine controls had radionuclide heart scans after intravenous hexarelin. The deficient men barely released growth hormone (peak 1.9 vs 45.7 µg/L), yet ejection fraction rose in both groups, from 50% to 57% and from 63% to 70%, without changes in catecholamines, blood pressure or cardiac output. The authors attribute the short-lived effect to heart receptors rather than growth hormone.
Hexarelin vs growth hormone itself
In seven male volunteers, growth hormone given into a vein and hexarelin raised circulating growth hormone to the same extent, but only hexarelin raised the ejection fraction, from 64.0% to 70.7%. The rise began within 15 minutes, peaked at 30 and lasted up to 60, with no significant change in blood pressure or heart rate. Hexarelin, and not growth hormone, also raised cortisol.
Less deep sleep
Seven young volunteers received four 50 µg doses of hexarelin or placebo, hourly from 10 pm to 1 am. Hexarelin reduced stage 4 sleep in the first half of the night and EEG delta power across the night, raised growth hormone and prolactin all night, and raised ACTH and cortisol in the first half. Leptin, TNF-alpha and its soluble receptors did not change.
Ghrelin released more
In seven young men given 1 µg/kg into a vein, the stomach hormone ghrelin released more growth hormone than hexarelin (mean peak 92.1 vs 68.4 µg/L), and both released more than GHRH (26.7 µg/L). Ghrelin also raised prolactin, ACTH and cortisol more than hexarelin did. Giving hexarelin with ghrelin did not change ghrelin's effects, whereas ghrelin and GHRH together were synergistic.
A test for Cushing's disease
In a randomised, single-blind study of eight alcoholics with pseudo-Cushing's syndrome, six patients with Cushing's disease and nine controls, hexarelin at 2 µg/kg into a vein caused striking ACTH and cortisol rises in Cushing's disease, a slight rise in controls and no significant change in the alcoholics. The authors propose it, like desmopressin, as a way to tell the two conditions apart.
The case for a heart receptor
A concise review of hexarelin's cardiovascular actions notes that the ghrelin receptor it binds is also found in the heart and blood vessels, and that CD36, a separate receptor, has been shown to be a specific cardiac receptor for hexarelin that mediates its protective effects. It describes hexarelin as more chemically stable and more potent than ghrelin, and suggests it may be a promising agent for some cardiovascular conditions.
First results in rats
Swapping GHRP-6's tryptophan for the more stable 2-methyl-tryptophan gave a peptide that strongly released growth hormone in conscious 10-day-old rats. In anaesthetised adult rats, intravenous hexarelin and GHRP-6 were equally effective, both peaking within 10 minutes; given under the skin, hexarelin produced a longer-lasting release and was slightly more effective than GHRP-6.
Half-life and elimination in rats
In rats, hexarelin given into a vein had a half-life of 75.9 minutes, and 64% of a dose given under the skin reached the blood, without accumulating across doses. Most of a radiolabelled dose left in bile (60%), with 22% in urine and 10% in faeces, and 90% of what reached the bile was unchanged hexarelin, which the authors read as resistance to protein-digesting enzymes.
Half-life in dogs
Using a new radioimmunoassay, researchers measured hexarelin in dogs after 1 µg/kg into a vein and 1, 10 and 100 µg/kg under the skin. The terminal half-life after the intravenous dose was 120 minutes. Clearance and volume of distribution stayed constant across the hundredfold range of doses.
Six weeks in beagles
Six beagles received 250 µg/kg under the skin twice daily for six weeks. The growth hormone response to a test dose of hexarelin rose to a peak at week 3, then fell below its starting level by week 6, while the response to GHRH returned to baseline. Hexarelin's acute feeding effect vanished at week 3 and came back by week 6.
One oral dose after a heart attack in mice
Mice given a single oral dose 30 minutes after an induced heart attack had better ejection fraction and fractional shortening, and less lung congestion, in the chronic phase than untreated mice, though deaths in the first 14 days did not differ. Treated mice had lower adrenaline and dopamine and a shift toward parasympathetic nervous activity.
Dosing Data
Hexarelin has no approved dose. The studies used per-kilogram doses: 0.5 to 2 µg/kg once into a vein for testing, and 1.5 µg/kg under the skin two or three times a day for courses. For a 70 kg adult, 1.5 µg/kg is about 105 µg.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
→ Full Hexarelin dosage guide — the community figures, the per-kilogram doses the studies used, and why a fading response shapes how people use it.
Side Effects & Contraindications
Reported Side Effects
These come from the small studies above, which ran from single doses to 16-week courses. Most measured hormones rather than symptoms.
Contraindications & Cautions
No trial defined who should avoid hexarelin. These cautions follow from what the studies measured.
Legal Status
Hexarelin is not approved as a medicine anywhere, under that name or as examorelin. Status as of September 26, 2026.
Frequently Asked Questions
?Is examorelin the same as hexarelin?
Yes. Examorelin is hexarelin's international nonproprietary name, and PubChem files both names, with the development codes EP 23905 and MF-6003, under one record (CID 6918297). This site also has an older examorelin entry, which now says it describes the same molecule.
?How much growth hormone does hexarelin release?
In 12 healthy men, single doses of 0.5, 1 and 2 µg/kg into a vein raised growth hormone to mean peaks of about 27, 52 and 55 ng/mL, against about 4 ng/mL after placebo, with the peak around 30 minutes; 2 µg/kg was close to the maximum. It released more than GHRH in short children and in healthy men, and less than ghrelin in a direct comparison.
?Does hexarelin stop working with repeated use?
Partly. After 16 weeks of twice-daily injections of 1.5 µg/kg, the growth hormone response to a test dose was about 45% smaller than at the start, and it returned to normal four weeks after stopping. IGF-1, body fat, lean mass and bone density did not change over the course. In beagles given high doses for six weeks, the response rose at three weeks and fell below baseline by six.
?What is hexarelin's half-life?
It has not been measured in people in any study we found. Given into a vein, hexarelin had a half-life of about 76 minutes in rats and 120 minutes in dogs. The figure of about 55 minutes often quoted, including on an earlier version of this page, is the half-life of the growth hormone it releases, from a 1994 dose-response study in men.
?Does hexarelin help the heart?
In two small studies a single dose into a vein raised the heart's ejection fraction by about seven percentage points within 15 to 30 minutes, for up to an hour, including in men with growth hormone deficiency. In mice it preserved heart function after induced heart attacks. No study tested it as a treatment in people with heart disease.
?Does hexarelin raise cortisol or prolactin?
Yes, after single doses. In children cortisol and prolactin rose slightly and returned to baseline within two hours; in a sleep study ACTH, cortisol and prolactin all rose overnight. The rises were smaller than after ghrelin. Over a 16-week course the cortisol response fell and prolactin did not change, and a day of two or three injections left 24-hour cortisol and prolactin unchanged.
References
- [pubmed] Imbimbo BP, et al. "Growth hormone-releasing activity of hexarelin in humans. A dose-response study." Eur J Clin Pharmacol, 1994;46(5):421-5. PMID: 7957536.
- [pubmed] Loche S, et al. "The growth hormone-releasing activity of hexarelin, a new synthetic hexapeptide, in short normal and obese children and in hypopituitary subjects." J Clin Endocrinol Metab, 1995;80(2):674-8. PMID: 7852535.
- [pubmed] Massoud AF, et al. "The effect of repeated administration of hexarelin, a growth hormone releasing peptide, and growth hormone releasing hormone on growth hormone responsivity." Clin Endocrinol (Oxf), 1996;44(5):555-62. PMID: 8762732.
- [pubmed] Rahim A, et al. "Growth hormone status during long-term hexarelin therapy." J Clin Endocrinol Metab, 1998;83(5):1644-9. PMID: 9589671.
- [pubmed] Rahim A, et al. "The effect of chronic hexarelin administration on the pituitary-adrenal axis and prolactin." Clin Endocrinol (Oxf), 1999;50(1):77-84. PMID: 10341859.
- [pubmed] Maccario M, et al. "Impact 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;146(3):310-8. PMID: 11888836.
- [pubmed] Bisi G, et al. "Cardiac effects of hexarelin in hypopituitary adults." Eur J Pharmacol, 1999;381(1):31-8. PMID: 10528131.
- [pubmed] Bisi G, et al. "Acute cardiovascular and hormonal effects of GH and hexarelin, a synthetic GH-releasing peptide, in humans." J Endocrinol Invest, 1999;22(4):266-72. PMID: 10342360.
- [pubmed] Frieboes RM, et al. "Hexarelin decreases slow-wave sleep and stimulates the secretion of GH, ACTH, cortisol and prolactin during sleep in healthy volunteers." Psychoneuroendocrinology, 2004;29(7):851-60. PMID: 15177700.
- [pubmed] Arvat E, et al. "Endocrine activities of ghrelin, a natural growth hormone secretagogue (GHS), in humans: comparison and interactions with hexarelin, a nonnatural peptidyl GHS, and GH-releasing hormone." J Clin Endocrinol Metab, 2001;86(3):1169-74. PMID: 11238504.
- [pubmed] Coiro V, et al. "Desmopressin and hexarelin tests in alcohol-induced pseudo-Cushing's syndrome." J Intern Med, 2000;247(6):667-73. PMID: 10886488.
- [review] Mao Y, et al. "The cardiovascular action of hexarelin." J Geriatr Cardiol, 2014;11(3):253-8. PMID: 25278975.
- [pubmed] Deghenghi R, et al. "GH-releasing activity of Hexarelin, a new growth hormone releasing peptide, in infant and adult rats." Life Sci, 1994;54(18):1321-8. PMID: 7910650.
- [pubmed] Roumi M, et al. "Kinetics and disposition of hexarelin, a peptidic growth hormone secretagogue, in rats." Drug Metab Dispos, 2000;28(1):44-50. PMID: 10611139.
- [pubmed] Roumi M, et al. "Radioimmunoassay for hexarelin, a peptidic growth hormone secretagogue, and its pharmacokinetic studies." Peptides, 1995;16(7):1301-6. PMID: 8545255.
- [pubmed] Rigamonti AE, et al. "Six-week treatment with hexarelin in young dogs: evaluation of the GH responsiveness to acute hexarelin or GHRH administration, and of the orexigenic effect of hexarelin." Eur J Endocrinol, 1999;141(3):313-20. PMID: 10474131.
- [pubmed] Mao Y, et al. "One dose of oral hexarelin protects chronic cardiac function after myocardial infarction." Peptides, 2014;56:156-62. PMID: 24747279.
Sources & Citations
Every citation on this page is PubMed-indexed and has been checked against its record. Four cited papers were added to our evidence set by hand because the search ranked them too low: the first human dose-response study, two animal studies that measured hexarelin's own half-life, and a 24-hour dosing study. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.