Hexarelin vs GHRP-6: what to choose and for whom
Peptide enthusiasts often argue about what is «better» - hexarelin or GHRP-6. The editorial team suggests looking at the question differently: for what tasks these molecules were studied at all, what of that reached medicine, and which alternatives today have real regulatory status.
How to frame the question «what to choose» correctly
Comparing two drugs makes sense when both are legal treatment options for a specific condition. With hexarelin and GHRP-6 the situation is different: neither has passed registration as a medicine, so the «choice» between them takes place outside the medical system.
In that case, comparison «by efficacy» loses meaning. A person does not know the exact content and purity of the product, has no label with contraindications, and a doctor cannot take responsibility for the use of an unregulated substance.
That is why we examine the topic from three angles: what the aim of the studies of each peptide was, which populations took part in them, and which registered drugs with a similar mechanism exist today.
This approach helps answer the real question that usually lies behind «what to choose»: is there a safe and legal way to achieve the desired result.
What GHRP-6 was studied for
After being described in 1984, GHRP-6 became primarily a tool of fundamental science. It was used to study the regulation of growth hormone secretion and ultimately led to the discovery of the GHS-R1a receptor and the hormone ghrelin.
In clinical endocrinology, GHRP-6 was used in research protocols as a stimulation test, notably in combination with GHRH, to assess the growth hormone reserve of the pituitary. This combination produced a very strong response in healthy people and a weak one in cases of pituitary damage.
Thanks to its pronounced effect on appetite, GHRP-6 was also studied in experimental models as a potential agent against wasting. However, this work did not lead to a registered indication.
Thus, the main «users» of GHRP-6 in science are researchers of the GH axis, not patients with a particular disease. For a healthy person seeking an athletic effect, there is effectively no clinical data.
What hexarelin was studied for
Hexarelin was developed as a more potent and more stable secretagogue. Ghigo et al. (1994) showed that it stimulates GH release by various routes of administration, which made it a promising candidate for the role of a diagnostic or therapeutic agent.
Subsequent studies revealed limitations: with prolonged use the GH response weakened, and the side stimulation of cortisol and prolactin was more noticeable than desired. This reduced interest in hexarelin as a means of long-term therapy.
Instead, the discovery of binding to the CD36 receptor (Bodart et al., 2002) directed research towards cardiology. Cardioprotective effects were studied mainly in animals, and the human data are limited to small samples.
So for hexarelin there is no group of patients for whom an advantage over standard treatment has been proven. Its place is experimental pharmacology.
Approved alternatives with a similar mechanism
The science of ghrelin mimetics did not stop at hexapeptides. The next generation are non-peptide molecules that can be taken orally and that have undergone full clinical trials.
Macimorelin is an oral ghrelin receptor agonist, approved by the FDA in 2017 as a diagnostic test for detecting growth hormone deficiency in adults. Its accuracy was compared with the standard insulin tolerance test (Garcia et al., 2018).
Anamorelin is another oral ghrelin mimetic, studied in cancer cachexia in the randomized Phase III ROMANA trials (Temel et al., 2016). In Japan it is approved for the treatment of cachexia in certain types of cancer.
These examples show that medicine uses the mechanism embodied in GHRP-6 and hexarelin, but in molecules with predictable pharmacokinetics, controlled quality and clear indications.
| Substance | Type | Status | For whom |
|---|---|---|---|
| GHRP-6 | Peptide, injectable | Not approved | Scientific research |
| Hexarelin | Peptide, injectable | Not approved | Scientific research |
| Macimorelin | Non-peptide, oral | FDA-approved (diagnostics) | Adults with suspected GH deficiency |
| Anamorelin | Non-peptide, oral | Approved in Japan | Patients with cancer cachexia |
Who these peptides are definitely not suitable for
Athletes subject to doping control: hexarelin, GHRP-6 and other growth hormone secretagogues are listed directly in section S2 of the WADA Prohibited List and are prohibited at all times.
People with carbohydrate metabolism disorders, since increasing growth hormone and IGF-1 can worsen insulin sensitivity. For GHRP-6, increased appetite is added to this, which complicates weight control.
People with a history of cancer, with hormone-dependent conditions, during pregnancy and breastfeeding - because of the unstudied safety profile and the potential effect of IGF-1 on tissue growth.
If, however, the goal is to improve recovery, body composition or sleep, it is worth starting with proven tools:
- sufficient sleep of 7-9 hours, since the greatest GH peak occurs during deep sleep;
- adequate protein and energy intake;
- structured strength and interval training;
- examination by an endocrinologist if there are symptoms of hormonal disorders.
Editorial conclusions
Between hexarelin and GHRP-6 there is no «right» choice for a healthy person: both are experimental peptides without approved indications. Hexarelin is more potent, but less selective and loses its effect faster; GHRP-6 is weaker and strongly increases appetite.
Medicine already has registered ghrelin mimetics - macimorelin for diagnostics and anamorelin for cachexia - but they are prescribed only for clear indications.
For athletes, both hexapeptides are prohibited, and for everyone else their use is an experiment without quality control.
We also recommend reading our materials «Hexarelin or GHRP-6: what's the difference», on the long-term risks of GHRP-6 and on how to tell a quality peptide from a counterfeit.
References
- Bowers CY, Momany FA, Reynolds GA, Hong A. On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone. Endocrinology. 1984;114(5):1537–1545.
- Howard AD, Feighner SD, Cully DF, et al. A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 1996;273(5277):974–977.
- Kojima M, Hosoda H, Date Y, et al. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 1999;402(6762):656–660.
- Ghigo E, Arvat E, Gianotti L, et al. Growth hormone-releasing activity of hexarelin, a new synthetic hexapeptide, after intravenous, subcutaneous, intranasal, and oral administration in man. J Clin Endocrinol Metab. 1994;78(3):693–698.
- Bodart V, Febbraio M, Demers A, et al. CD36 mediates the cardiovascular action of growth hormone-releasing peptides in the heart. Circ Res. 2002;90(8):844–849.
- Garcia JM, Biller BMK, Korbonits M, et al. Macimorelin as a diagnostic test for adult GH deficiency. J Clin Endocrinol Metab. 2018;103(8):3083–3093.
- Temel JS, Abernethy AP, Currow DC, et al. Anamorelin in patients with non-small-cell lung cancer and cachexia (ROMANA 1 and ROMANA 2): results from two randomised, double-blind, phase 3 trials. Lancet Oncol. 2016;17(4):519–531.
- World Anti-Doping Agency. The World Anti-Doping Code International Standard: Prohibited List. Montreal: WADA; актуальна редакція.
Andriy Melnyk
A strength-sports coach and author of programs for beginner and intermediate levels. Writes about training planning.
