Hexarelin Evidence Guide
Hexarelin has Phase 2 human data on GH release and cardioprotective effects, but its side-effect profile - significant cortisol and prolactin elevation, rapid desensitization - makes it a poor practical starting point compared to ipamorelin. The cardiac GHS-R1a data is scientifically interesting, but the compound's limitations are real. Ipamorelin is a cleaner choice for GH secretagogue research; hexarelin is mainly useful for studying GHRP receptor pharmacology specifically.
Our Take
Hexarelin has Phase 2 human data on GH release and cardioprotective effects, but its side-effect profile - significant cortisol and prolactin elevation, rapid desensitization - makes it a poor practical starting point compared to ipamorelin. The cardiac GHS-R1a data is scientifically interesting, but the compound's limitations are real. Ipamorelin is a cleaner choice for GH secretagogue research; hexarelin is mainly useful for studying GHRP receptor pharmacology specifically.
- Best for
- GHRP receptor pharmacology, cardioprotective GH secretagogue research
- Evidence grade
- Level C
- Confidence
- Moderate
- Starting point
- 100mcg subcutaneous, up to three times daily (short-term only due to desensitization)
Benefits and Evidence
- Growth Hormone Release: Level B, includes human evidence - One of the most potent GH secretagogues studied, producing significant acute GH release in healthy volunteers and GH-deficient patients.
- Cardioprotection: Level C, includes human evidence - Improved cardiac function parameters including ejection fraction and cardiac output in patients with heart failure, mediated through GH-independent CD36 pathways.
- Cortisol and Prolactin Elevation: Level B, includes human evidence - Transient increases in cortisol and prolactin levels observed after administration, generally returning to baseline within a few hours.
Side Effects and Warnings
- Flushing
- Transient cortisol elevation
- Increased appetite
- Water retention
- Tingling and numbness
- Drowsiness
- Not approved for clinical use
- Tachyphylaxis occurs with continuous use - intermittent dosing recommended
Research Dosage References
- <strong>Subcutaneous injection</strong> - 100-200 mcg - 2-3 times daily - Research dosage. Typically administered 30 minutes before meals or exercise for optimal GH release.
- <strong>Intravenous</strong> - 1-2 mcg/kg - Single dose (diagnostic use) - Used in clinical studies as a GH stimulation test. Produces peak GH response within 15-30 minutes.
Mechanism of Action
Hexarelin stimulates growth hormone release through a dual mechanism involving both ghrelin receptor (GHSR1a) activation and a GHSR-independent pathway. It binds to GHSR1a on somatotroph cells in the anterior pituitary, triggering GH secretion through inositol triphosphate and diacylglycerol signaling cascades. The cardioprotective effects of hexarelin appear to be mediated through a distinct mechanism involving scavenger receptor CD36 on cardiac cells. Binding to CD36 activates cardioprotective signaling pathways including PPAR-gamma activation and suppression of cardiac cell apoptosis. These effects are independent of GH release and have been demonstrated in GH-deficient animal models. Hexarelin is one of the most potent synthetic GHRPs, producing robust GH release that is greater than GHRP-6 and comparable to GHRH itself. However, like other GHRPs, it is subject to tachyphylaxis (diminishing response) with continuous administration, likely due to receptor desensitization.
Legal Status
Not FDA approved. Available as a research chemical. Banned by WADA in competitive sports.
Primary Sources
- Hexarelin, a synthetic growth hormone-releasing peptide, has cardioprotective effects in GH-deficient rats. Endocrinology, 1999.
- Cardiac effects of hexarelin in patients with severe heart failure. European Journal of Pharmacology, 2002.