In healthy people GHRP-6 released about 3 times more growth hormone than GHRH, the natural hormone that does this in the body. Given together with GHRH, it produced almost 8 times more growth hormone than GHRH alone, clearly more than the sum of both effects. In older women it also worked when swallowed, and its strength did not fade after four days of dosing. The half-life of GHRP-6 in the blood is about 2.5 hours. Below we gather the studies in humans, from a single dose to a phase 3 trial from 2026.
What is GHRP-6?
GHRP-6 is a short peptide of six amino acids, and its name means growth hormone releasing peptide. It works through the receptor for ghrelin, the hunger hormone, which is a different route from GHRH. That is why the two groups of peptides can strengthen each other.
GHRP-2, ipamorelin and hexarelin use the same receptor. How these molecules differ from one another is described in the guide on how GHRP-2, GHRP-6 and ipamorelin differ. The general principles of both groups are explained in the guide on how GHRH, GHRP and ghrelin work.
How much growth hormone does GHRP-6 release in humans?
The clearest comparison came from a 1995 study in Belgrade. Eleven healthy people received GHRH, GHRP-6 or both peptides at once, intravenously on three separate days. The researchers measured the total amount of growth hormone over 120 minutes after dosing.
| What was given | Growth hormone over 120 minutes | Compared with GHRH alone |
|---|---|---|
| GHRH 100 µg | 483.7 | 1 time |
| GHRP-6 90 µg | 1434.8 | about 3 times more |
| GHRH and GHRP-6 together | 3771.5 | almost 8 times more |
The values are the area under the curve in micrograms per litre. The result of both peptides together was significantly higher than the sum of each one alone. The researchers called this a clear synergistic action.
In people whose hypothalamus was cut off from the pituitary, GHRP-6 barely worked. The authors concluded that GHRP-6 acts mainly through the hypothalamus, not only directly on the pituitary.
How long does GHRP-6 stay in the blood?
The pharmacokinetics of GHRP-6 were studied in 2013 in Cuba in nine healthy men. They received a single intravenous dose of 100, 200 or 400 micrograms per kilogram of body weight. The researchers measured the peptide level with a special chromatography method with mass detection.
- Distribution phase: half-life of about 7.6 minutes.
- Elimination phase: half-life of about 2.5 hours.
- Dose dependence: the amount of peptide in the blood rose in proportion to the dose.
- After 12 hours: the level fell to the detection limit of the method.
The half-life of GHRP-6 is therefore short compared with long-acting peptides. A comparison for many molecules is given in the guide on how long a peptide stays in the body.
Does GHRP-6 work in older people?
Yes, as researchers in Turin showed in two studies in 1994. With age the pituitary responds less and less to GHRH. GHRP-6 made it possible to partly get around this weaker response.
| Study | Who | Peak growth hormone |
|---|---|---|
| Ghigo, J Endocrinol Invest 1994 | 8 young and 8 older people, GHRP-6 by mouth | young 16.2 µg/l, older 9.9 µg/l |
| Same study | older people, GHRP-6 with 8 g of arginine by mouth | 22.1 µg/l, more than in the young |
| Ghigo, Eur J Endocrinol 1994 | 7 women aged 65 to 82, GHRP-6 by mouth | 10.7 µg/l versus 5.1 µg/l after GHRH into a vein |
| Same study, after 4 days | GHRP-6 twice a day | 16.8 µg/l, response maintained |
In older women GHRP-6 swallowed in a capsule gave a higher growth hormone peak than GHRH given straight into a vein. After four days of taking it twice a day the response did not weaken, and it even tended to rise. IGF-1 did not change significantly after such a short time: 77.1 before and 84.1 µg/l after.
In the arginine study, older people given GHRP-6 with arginine released more growth hormone than the young after any stimulus. In the young, arginine did not change the response.
Does the route of administration matter?
A great deal, as a 1999 study in Munich showed. Young men received GHRP-6 in the evening in three forms, and the researchers measured hormones and sleep recordings through the whole night.
- Into the nose, 30 µg/kg: a significant rise in growth hormone through the whole night.
- Under the tongue, 30 µg/kg: only a trend towards a rise in the first half of the night.
- By mouth in a capsule, 300 µg/kg: no change in growth hormone.
In an earlier study by the same team, GHRP-6 given intravenously raised growth hormone, ACTH and cortisol and lengthened the second stage of sleep. The authors concluded that the effect depends on the dose, timing and route of administration. We write more about peptides and sleep in the guide on growth hormone peptides and sleep.
Where has GHRP-6 been tested in medicine?
The combination of GHRH with GHRP-6 is used as a diagnostic test for growth hormone deficiency in adults. In a 2003 multicentre study it was tested in 50 patients and 100 healthy people. The test had a sensitivity of 94.4 percent and a specificity of 98.8 percent, so it reliably told patients from healthy people.
In 2026 the Cuban phase 3 trial COURAGE-2 was published, in 188 people after acute ischaemic stroke. Treated patients received epidermal growth factor and 5 mg of GHRP-6 twice a day intravenously for 7 days. In the group as a whole the result did not differ from standard treatment. In a subgroup of 27 people with severe stroke, however, those treated had less disability at 6 months and a lower risk of death. In treated patients with stroke in the middle cerebral artery area, the stroke lesion shrank more. None of the serious events were linked to the treatment.
What should you watch for with GHRP-6?
GHRP-6 works through the ghrelin receptor, so it clearly increases appetite. For some this is a drawback, and for people who find it hard to eat a lot of calories it is an advantage. The details are in the guide on which peptides curb appetite and which increase it.
In the Munich study, GHRP-6 given into the nose showed a trend towards a rise in ACTH, the hormone that stimulates the adrenal glands. GHRP-6 is not an approved medicine.
Where to buy GHRP-6 and how much does it cost?
The shop has three 10 mg vials of GHRP-6, all in stock:
- GHRP-6 10 mg Genheal costs 20 EUR,
- GHRP-6 10 mg Bio-Peptide costs 20 EUR,
- GHRP-6 10 mg Nouveaux Ltd. costs 25 EUR.
The synergy with GHRH is used by ready-made blends of GHRP-6 with CJC-1295, a GHRH analogue. The Bio-Peptide blend and the Genheal blend cost 30 EUR each, and the Nouveaux Ltd. blend 35 EUR, on backorder. All variants are gathered on the GHRP-6 and GHRP-6 and CJC-1295 pages. We write about the advantages of such blends in the guide on ready-made blends in one vial. The products in the shop are material for laboratory research, not a medicine.
Frequently asked questions
How much growth hormone does GHRP-6 release?
In a 1995 study GHRP-6 released about 3 times more growth hormone than GHRH in healthy people, measured over 120 minutes after intravenous dosing.
Does GHRP-6 work better with GHRH?
Yes, the two peptides given together produced almost 8 times more growth hormone than GHRH alone, more than the sum of their separate effects.
How long does GHRP-6 stay in the blood?
In healthy men the half-life in the elimination phase was about 2.5 hours, and in the distribution phase about 7.6 minutes.
Does GHRP-6 work in older people?
Yes, in women aged 65 to 82 GHRP-6 by mouth gave a higher growth hormone peak than GHRH into a vein, and the response held after 4 days of dosing.
How much does GHRP-6 cost in the shop?
A 10 mg vial costs 20 EUR from Genheal and Bio-Peptide and 25 EUR from Nouveaux Ltd. Blends with CJC-1295 cost from 30 EUR.
Sources
- Popovic V, Damjanovic S, Micic D et al. Blocked growth hormone-releasing peptide (GHRP-6)-induced GH secretion and absence of the synergic action of GHRP-6 plus GH-releasing hormone in patients with hypothalamopituitary disconnection. Journal of Clinical Endocrinology and Metabolism, 1995, 80(3): 942-947. https://doi.org/10.1210/jcem.80.3.7883854
- Cabrales A, Gil J, Fernández E et al. Pharmacokinetic study of growth hormone-releasing peptide 6 (GHRP-6) in nine male healthy volunteers. European Journal of Pharmaceutical Sciences, 2013, 48(1-2): 40-46. https://doi.org/10.1016/j.ejps.2012.10.006
- Ghigo E, Arvat E, Rizzi G et al. Arginine enhances the growth hormone-releasing activity of a synthetic hexapeptide (GHRP-6) in elderly but not in young subjects after oral administration. Journal of Endocrinological Investigation, 1994, 17(3): 157-162. https://doi.org/10.1007/BF03347707
- Ghigo E, Arvat E, Rizzi G et al. Growth hormone-releasing activity of growth hormone-releasing peptide-6 is maintained after short-term oral pretreatment with the hexapeptide in normal aging. European Journal of Endocrinology, 1994, 131(5): 499-503. https://doi.org/10.1530/eje.0.1310499
- Frieboes RM, Murck H, Antonijevic IA, Steiger A. Effects of growth hormone-releasing peptide-6 on the nocturnal secretion of GH, ACTH and cortisol and on the sleep EEG in man: role of routes of administration. Journal of Neuroendocrinology, 1999, 11(6): 473-478. https://doi.org/10.1046/j.1365-2826.1999.00364.x
- Popovic V, Pekic S, Doknic M et al. The effectiveness of arginine + GHRH test compared with GHRH + GHRP-6 test in diagnosing growth hormone deficiency in adults. Clinical Endocrinology, 2003, 59(2): 251-257. https://doi.org/10.1046/j.1365-2265.2003.01835.x
- Hernández-Bernal F, Subirós-Martínez N, Gutiérrez-Ronquillo JH et al. Phase III open-label, randomized clinical trial of epidermal growth factor and growth hormone releasing hexapeptide in acute ischemic stroke. Journal of Clinical Neuroscience, 2026, 152: 112195. https://doi.org/10.1016/j.jocn.2026.112195