MK-677 (Ibutamoren) vs PEG-MGF
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.
MK-677 (Ibutamoren)
Oral non-peptide growth hormone secretagogue that mimics ghrelin to stimulate GH and IGF-1 release without injection. Long half-life (~24 hours) enables once-daily oral dosing. Widely researched for body composition, sleep quality, and IGF-1 elevation.
Full profilePEG-MGF
PEG-MGF is Mechano Growth Factor (MGF) conjugated to a polyethylene glycol (PEG) polymer chain. The PEGylation dramatically extends the half-life from ~5 minutes (native MGF) to approximately 24–72 hours, allowing less frequent dosing and systemic distribution rather than purely local action. This trade-off — longer duration vs localized intensity — makes PEG-MGF a different tool than native MGF, better suited for systemic muscle recovery support and convenience-focused protocols.
Full profile| MK-677 (Ibutamoren) | PEG-MGF | |
|---|---|---|
| Category | Performance & Growth Hormone | Performance & Growth Hormone |
| Also known as | Ibutamoren, Nutrobal, MK677, L-163,191 | PEGylated Mechano Growth Factor, Polyethylene Glycol-MGF, Long-acting MGF |
| Evidence | Research-stage | Preclinical only |
| Dosing range | 10mg–50mg mg, once daily oral | 100mcg–400mcg mcg, 2x weekly (Monday/Thursday or similar split) |
| Administration | Oral (capsule/liquid) | Subcutaneous injection (preferred for systemic distribution), Intramuscular injection |
| Key side effects | Water retention, Increased appetite, Elevated fasting glucose (long-term), Fatigue (initial, transient) | Hypoglycemia (less pronounced than IGF-1 DES, more than native MGF due to systemic distribution), Generalized fatigue on injection days, PEG accumulation concern with very high doses over long periods (theoretical — not established at research doses), Localized injection site swelling |
| Cited sources | 2 references | 2 references |
Key differences
- Evidence level differs: MK-677 (Ibutamoren) is research-stage, while PEG-MGF is preclinical only.
- Administration: MK-677 (Ibutamoren) — Oral (capsule/liquid); PEG-MGF — Subcutaneous injection (preferred for systemic distribution), Intramuscular injection.
- Dosing units differ: MK-677 (Ibutamoren) is dosed in mg, PEG-MGF in mcg — they operate at different scales.
- Frequency: MK-677 (Ibutamoren) is typically once daily oral; PEG-MGF is 2x weekly (Monday/Thursday or similar split).
How each works
MK-677 (Ibutamoren)
MK-677 binds the ghrelin receptor (GHS-R1a) to stimulate pulsatile GH release and increase circulating IGF-1. Unlike peptide GHRPs it survives oral administration. Clinical trials demonstrate significant increases in GH pulsatility and IGF-1 without suppression of the endogenous GH axis, though long-term use raises glucose metabolism concerns.
PEG-MGF
PEGylation is a validated pharmaceutical strategy for extending peptide half-life (used in Pegasys/interferon, Somavert/pegvisomant, and others). The PEG chain shields the MGF peptide from proteolytic degradation and slows renal clearance. Research in rodent models confirms PEG-MGF preserves the biological activity of native MGF (satellite cell activation, muscle repair) with extended duration. Unlike native MGF which requires precise post-workout injection timing, PEG-MGF can be injected on a scheduled basis and still achieves systemic muscle-wide satellite cell 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.