GHRP-6 vs Melanotan II
A neutral, side-by-side comparison of two performance & growth hormone peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
GHRP-6
GHRP-6 is a first-generation synthetic hexapeptide GH secretagogue that strongly stimulates pituitary GH release via ghrelin receptor activation. It is one of the oldest and most well-studied GHRPs, with a large body of research spanning more than three decades. GHRP-6 produces significant GH pulses but is notable for powerfully stimulating appetite — a side effect that can be beneficial for those in a caloric deficit or disadvantageous for those managing body composition.
Full profileMelanotan II
Melanotan II (MT-II) is a cyclic lactam analog of alpha-melanocyte stimulating hormone (α-MSH) that acts as a potent, non-selective melanocortin receptor agonist (MC1R, MC3R, MC4R, MC5R). Developed at the University of Arizona in the late 1980s, it produces eumelanin-driven skin darkening (tanning) via MC1R, sexual arousal and spontaneous erections via MC4R, and appetite suppression via MC3R/MC4R. Bremelanotide (PT-141) — now FDA-approved for female sexual dysfunction — was derived from Melanotan II.
Full profile| GHRP-6 | Melanotan II | |
|---|---|---|
| Category | Performance & Growth Hormone | Performance & Growth Hormone |
| Also known as | Growth Hormone Releasing Peptide-6, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 | MT-II, MTII, Cyclo[Nle4,D-Phe7]-α-MSH |
| Evidence | Preclinical only | Research-stage |
| Dosing range | 100mcg–300mcg mcg, 1–3 times daily, on an empty stomach | 250mcg–1000mcg mcg, Daily during loading phase; 2–3x weekly for maintenance |
| Administration | Subcutaneous injection, Intramuscular injection | Subcutaneous injection (most common), Intranasal (less effective, lower bioavailability) |
| Key side effects | Strong increase in appetite (most common and notable), Elevated cortisol and prolactin at higher doses, Water retention / bloating, Fatigue at high doses | Nausea (most common — especially first 30–60 minutes post-injection), Facial flushing, Spontaneous erections (males — often unwanted at higher doses), Fatigue / yawning post-injection |
| Cited sources | 3 references | 3 references |
Key differences
- Evidence level differs: GHRP-6 is preclinical only, while Melanotan II is research-stage.
- Administration: GHRP-6 — Subcutaneous injection, Intramuscular injection; Melanotan II — Subcutaneous injection (most common), Intranasal (less effective, lower bioavailability).
- Frequency: GHRP-6 is typically 1–3 times daily, on an empty stomach; Melanotan II is Daily during loading phase; 2–3x weekly for maintenance.
How each works
GHRP-6
Human studies confirm GHRP-6 robustly elevates GH within 15–30 minutes of injection, with effects diminishing toward baseline within 2–3 hours. Chronic use increases baseline IGF-1. Research also indicates mild stimulation of cortisol and prolactin, particularly at higher doses. Animal models have shown potential cardioprotective, hepatoprotective, and muscle-sparing effects, though human equivalents are not established.
Melanotan II
Melanotan II's broad melanocortin receptor agonism produces a constellation of effects across multiple systems. MC1R activation in melanocytes upregulates tyrosinase, the rate-limiting enzyme in melanin synthesis, producing UV-independent skin darkening. MC4R activation in the CNS and spinal cord drives sexual arousal and erectogenic effects more potent than most PDE5 inhibitors, and also produces appetite suppression and reduced food intake (the same pathway exploited by weight-loss drugs targeting the melanocortin system). MC3R activation contributes to energy homeostasis effects.
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.