Overview
Hexarelin (His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2) is a synthetic hexapeptide growth hormone secretagogue that ranks among the most potent GH-releasing peptides ever developed. First synthesized by researchers at the Università degli Studi di Milano, Hexarelin produces a GH release approximately 2–3 times greater than GHRP-6 and significantly stronger than Ipamorelin, making it the most powerful peptide GH secretagogue available.
What distinguishes Hexarelin from other GH secretagogues is its unique cardioprotective activity, mediated through binding to the CD36 scavenger receptor on cardiac cells. This cardiac effect is independent of GH release and represents a direct protective mechanism against ischemia-reperfusion injury, cardiac fibrosis, and atherosclerotic plaque formation. No other GH secretagogue demonstrates this dual GH/cardiac activity.
Hexarelin has been studied in multiple human clinical trials, including investigations of its effects on growth hormone deficiency, cardiac function post-myocardial infarction, and body composition in elderly subjects. While it has not received regulatory approval, the clinical dataset for Hexarelin is more extensive than for most peptide GH secretagogues.
This guide reviews Hexarelin's pharmacology, its unique cardioprotective mechanism, clinical evidence, and important considerations regarding its potent GH-releasing effects and tendency to induce desensitization with chronic use.
Quick facts
- Mechanism
- Potent GHS-R1a agonist with CD36-mediated cardioprotection
- Primary use
- Growth Hormone Release & Cardiac Protection
- Evidence
- moderate
- FDA
- Not approved
- Route
- Subcutaneous or intravenous injection
- Typical results
- Robust GH release within 15–30 minutes; cardioprotective effects in clinical studies
Chemical information
Hexarelin (C₄₇H₅₈N₁₂O₆) is a gh secretagogue compound with a molecular weight of 887.06 g/mol. Its structural characteristics underpin its biological activity in growth hormone secretion.
How Hexarelin works
Hexarelin acts as a potent agonist at the growth hormone secretagogue receptor 1a (GHS-R1a) in the hypothalamus and pituitary, stimulating robust GH release through the same receptor targeted by ghrelin. However, Hexarelin's binding affinity and GH-releasing potency exceed those of natural ghrelin, producing GH pulses 2–3 times larger than those achieved with GHRP-6 or GHRP-2.
The cardioprotective effects of Hexarelin operate through an entirely separate receptor system—CD36 (cluster of differentiation 36), a class B scavenger receptor expressed on cardiomyocytes, macrophages, and endothelial cells. Hexarelin's binding to cardiac CD36 activates PPARγ signaling, reduces apoptotic signaling in ischemic cardiomyocytes, and promotes the clearance of oxidized low-density lipoproteins from the vascular wall.
In ischemia-reperfusion models, Hexarelin administered before or during reperfusion significantly reduces infarct size, preserves left ventricular function, and attenuates cardiac fibrosis. These effects have been confirmed in multiple animal models and are reproducible even in GH-deficient animals, confirming that cardioprotection is independent of GH release.
A significant limitation of Hexarelin is its tendency to induce pituitary desensitization with continuous use. Unlike Ipamorelin, which produces consistent GH release over extended periods, Hexarelin's potent GHS-R1a activation can downregulate receptor expression within 4–8 weeks of daily use, resulting in diminished GH response. This necessitates cycling protocols for sustained GH effects.
- GHS-R1a agonism: Most potent peptide activator of the ghrelin receptor, producing robust GH pulses
- CD36 binding: Unique cardioprotective mechanism independent of GH release
- PPARγ activation: Cardiac CD36 binding activates peroxisome proliferator-activated receptor gamma
- Anti-ischemic: Reduces infarct size and preserves cardiac function in ischemia-reperfusion
- IGF-1 elevation: Sustained GH release leads to significant IGF-1 increases
- Desensitization risk: Potent GHS-R1a activation leads to receptor downregulation with chronic use
Pharmacokinetics
| Parameter | Value | Significance |
|---|---|---|
| GH peak | 15–30 minutes post-injection | Rapid, robust GH pulse |
| GH elevation duration | ~2–3 hours | Potent but relatively short GH pulse |
| Half-life | ~70 minutes | Longer than GHRP-6; supports once-daily dosing |
| Desensitization onset | 4–8 weeks of daily use | Necessitates cycling (4 weeks on, 4 weeks off) |
| Cortisol elevation | Moderate (dose-dependent) | Greater cortisol stimulation than Ipamorelin |
Dosing & administration
Hexarelin dosing varies by indication and individual factors. No FDA-approved dosing exists for this compound; protocols in the literature derive from limited clinical or preclinical data and practitioner experience.
Any use should be conducted under qualified medical supervision with appropriate monitoring of safety markers.
Important: These dosing ranges are not FDA-approved. Any use should be under qualified medical supervision.
Side effects & safety
Safety data for Hexarelin is primarily derived from preclinical studies and limited human data. Long-term effects in humans remain incompletely characterized.
Common
- • Increased appetite (ghrelin receptor-mediated)
- • Transient cortisol elevation
- • Flushing and warmth post-injection
- • Water retention
- • Numbness or tingling
- • Mild headache
- • Vivid dreams
Serious / potential risks
- • Prolactin elevation (more pronounced than with Ipamorelin)
- • Cortisol spikes (significant at higher doses)
- • Pituitary desensitization with chronic daily use
- • Potential insulin resistance with long-term GH elevation
Drug interactions
| Medication | Interaction | Recommendation |
|---|---|---|
| Exogenous GH | Additive GH/IGF-1 elevation with increased side effect risk | Generally not combined; choose one GH-elevating approach |
| Insulin | GH antagonizes insulin; may increase glucose levels | Monitor blood glucose; adjust insulin doses accordingly |
| Glucocorticoids | Hexarelin elevates cortisol; additive adrenal effects | Monitor cortisol levels; avoid in Cushing's patients |
| GHRH analogs (CJC-1295) | Synergistic GH release through complementary mechanisms | Well-established combination; use lower doses of each |
Storage & handling
Lyophilized (powder)
- • Store at -20°C to 4°C (freezer or refrigerator)
- • Protect from light and moisture
- • Stable for 12–24 months when stored properly
- • Keep in original sealed container until reconstitution
Reconstituted solution
- • Refrigerate at 2–8°C after reconstitution
- • Use bacteriostatic water for multi-dose reconstitution
- • Typical stability: 14–28 days refrigerated
- • Do not freeze reconstituted solution
Cost & availability
| Source | Cost | Notes |
|---|---|---|
| Research peptide suppliers | $25–$50 per 5mg vial | Standard lyophilized peptide format |
| Compounding pharmacies | $100–$250 per month | Prescription required; higher purity |
The bottom line
Hexarelin is the most potent peptide GH secretagogue with the unique addition of cardioprotective properties via CD36 receptor binding. Its clinical evidence base is solid, particularly for cardiac applications. However, its tendency to desensitize the pituitary with chronic use and its effects on cortisol and prolactin make it less ideal than Ipamorelin for sustained GH therapy.
Best for
- • Short-term GH optimization protocols with cycling
- • Researchers studying cardiac protection via CD36 pathway
- • Individuals with cardiac risk factors under cardiologist supervision
- • Those seeking maximum GH release potency in short-term protocols
Not for
- • Long-term continuous GH therapy (desensitization risk)
- • Individuals with prolactinoma or hyperprolactinemia
- • Those sensitive to cortisol elevation
- • Self-administration without hormonal monitoring
Related compounds
Ipamorelin
More selective GH secretagogue without cortisol/prolactin elevation
GHRP-2
Potent GH secretagogue with intermediate selectivity profile
GHRP-6
Classic GH secretagogue with strong appetite stimulation
MK-677
Oral ghrelin mimetic offering GH elevation without injections
Frequently asked questions
References
- [1] Bisi G, Podio V, Valetto MR, et al.. Acute cardiovascular and hormonal effects of GH and hexarelin, a synthetic GH-releasing peptide, in humans. J Endocrinol Invest (1999). doi: 10.1007/BF03343617 PMID: 10091625
- [2] Bodart V, Febbraio M, Bhatt RK, et al.. CD36 mediates the cardiovascular action of growth hormone-releasing peptides in the heart. Circ Res (2002). doi: 10.1161/01.RES.0000035178.63242.95 PMID: 12065325
- [3] Broglio F, Koetsveld PV, Benso A, et al.. Ghrelin secretion is inhibited by either somatostatin or cortistatin in humans. J Clin Endocrinol Metab (2002). doi: 10.1210/jc.2002-020956
- [4] Locatelli V, Rossoni G, Schweiger F, et al.. Growth hormone-independent cardioprotective effects of hexarelin in the rat. Endocrinology (1999). doi: 10.1210/endo.140.9.6946 PMID: 10465271
- [5] Ghigo E, Arvat E, Muccioli G, Camanni F.. Growth hormone-releasing peptides. Eur J Endocrinol (1997). doi: 10.1530/eje.0.1370006 PMID: 9014756