Met-enkephalin is an endogenous pentapeptide Tyr-Gly-Gly-Phe-Met in the endogenous opioid class and a ligand of delta and mu opioid receptors. Unlike endorphins, which are produced mainly in the brain, met-enkephalin is synthesized widely—in the CNS, adrenals, immune cells, and gut—defining its role as a polysystem neuromodulator. Binding to opioid receptors on immune cells activates them: lymphocyte proliferation, NK cytotoxicity, and interleukin production increase, whereas classic opioid analgesics typically suppress immunity.
That immunostimulatory potential has been studied in oncology: at very low doses, met-enkephalin activates receptors on tumor cells and induces apoptosis while strengthening NK control of tumor progression. Use within low-dose naltrexone (LDN) therapy intersects the enkephalin system—brief opioid receptor blockade by naltrexone triggers compensatory met-enkephalin rise and subsequent immune activation. Via delta receptors, met-enkephalin is also neuroprotective: it reduces glutamate excitotoxicity, modulates dopaminergic and serotonergic transmission, and participates in mood regulation and stress response.
In chronic pain, met-enkephalin provides analgesia through mu and delta receptors with substantially lower habituation risk than synthetic opioids—largely because levels are regulated by physiological feedback and the peptide is rapidly degraded by enkephalinases. Clinical data on high, systematic human doses remain limited; the evidence base is predominantly preclinical and mechanistic.
🛡️ Immune activation (NK cells, lymphocytes): ★★★★☆
🧠 Neuromodulation and mood (delta/mu): ★★★★☆
🔥 Oncology and apoptotic potential (preclinical): ★★★☆☆
✅ Safety: ★★★☆☆ (endogenous molecule; little human data at high doses)
⚠️ Possible sensations and side effects: opioid profile at high doses; individual response
🤝 Combinations (goal → stack)
🛡️ Immune background + oncology support → Met-Enkephalin + Thymosin Alpha 1
🧠 Neuromodulation + neuroprotection → Met-Enkephalin + 9-Me-BC
🔥 Inflammation + immune regulation → Met-Enkephalin + KPV
| CAS number | 58569-55-4 |
| Batch purity | 99.19 % |
Full details in our guide
https://peptideboost.club/guide/met-enkephalin
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