GHRP-2
A synthetic ghrelin mimetic used clinically in Japan as a diagnostic test for growth hormone deficiency. Reliably raises GH; also raises cortisol and prolactin.
Growth Hormone
Hexarelin
The most potent of the classical GHRPs for raising growth hormone, but it desensitises the receptor faster than the others. Also studied for direct cardiac effects.
Overview
Hexarelin produces the largest single growth hormone spike of the older GHRP family. Its problem is tachyphylaxis: the response fades noticeably with repeated dosing over days to weeks, so the effect that makes it attractive is also the shortest-lived. It has a second, separate story — it binds a receptor called CD36 in heart tissue, and animal work suggests protective effects on the heart independent of growth hormone.
A synthetic hexapeptide GHS-R1a agonist, His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2. Produces the highest peak GH response of the classical GHRPs but shows pronounced receptor desensitisation with repeated administration. Distinctly among GHRPs, it binds CD36, a scavenger receptor expressed in cardiomyocytes and macrophages, and preclinical work reports reduced infarct size and improved cardiac function in ischaemia-reperfusion models independent of GH release. Also elevates cortisol and prolactin.
Research areas
Growth hormone axisCardiac protectionCD36 signalling
Dosing reported in the literature
Every protocol below is reproduced from a published study or approved labelling, with its source named. These are records of what was studied — not recommendations, and not a suggestion that any of them is appropriate for any person.
| Protocol as reported | Source |
|---|---|
| Subcutaneous 1.5 mcg/kg twice daily with GH response measured over 16 weeksResponse attenuated over the treatment period, which is the key finding. | Rahim et al., Clinical Endocrinology 1998 |
| Intravenous 2 mcg/kg as a single GH provocation dose | Human GH secretagogue provocation literature |
Trial status
Short and medium-term human pharmacodynamic studies. Cardiac work is preclinical.
Reported safety signals
- Receptor desensitisation with repeated dosing is documented, not theoretical.
- Raises cortisol and prolactin.
- Cardiac effects via CD36 are not characterised in humans and should not be assumed beneficial.
- No long-term human safety data.
Common questions
Why does hexarelin stop working?
Repeated stimulation of the GHS receptor downregulates the response — a 16-week study showed the growth hormone rise falling substantially over the treatment period. That desensitisation is more pronounced with hexarelin than with the other secretagogues.
Primary sources
Medical disclaimer
This page is for informational and research purposes only. Nothing here constitutes medical advice. The compounds discussed are research chemicals. Consult a qualified clinician before starting any protocol.
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