Ghrelin vs 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.
Ghrelin
Endogenous 28-amino acid peptide secreted primarily by the stomach that functions as both the primary hunger signal and a potent growth hormone secretagogue. The n-octanoyl modification at Ser-3 (acylated form) is required for GHS-R1a receptor binding and GH-stimulating activity. Understanding ghrelin explains the mechanism behind the entire GHRP class of research peptides.
Full profileMGF
MGF (Mechano Growth Factor) is a splice variant of IGF-1 produced locally in muscle tissue in response to mechanical loading (exercise, especially eccentric loading). Unlike circulating IGF-1 which is produced primarily by the liver, MGF is generated within the muscle itself and acts locally to activate satellite cells (muscle stem cells) — the cells responsible for muscle repair, growth, and adaptation. It is considered the primary local anabolic signal generated by resistance training.
Full profile| Ghrelin | MGF | |
|---|---|---|
| Category | Performance & Growth Hormone | Performance & Growth Hormone |
| Also known as | GHRL, growth hormone-releasing peptide endogenous, ghrelinergic peptide, acyl ghrelin | Mechano Growth Factor, IGF-1Ec, Insulin-like Growth Factor splice variant |
| Evidence | Investigational (in trials) | Preclinical only |
| Dosing range | 0.5mcg/kg–2mcg/kg mcg/kg, IV or SC bolus; endogenous levels peak pre-meal | 100mcg–300mcg mcg, Post-workout (within 30–60 minutes of training), 3–4x weekly |
| Administration | Intravenous (research), Subcutaneous injection | Intramuscular injection (into worked muscle — critical for local effect), Subcutaneous injection (produces more systemic distribution) |
| Key side effects | Appetite stimulation, Transient hyperglycemia, Water retention, GH pulse stimulation | Localized muscle swelling at injection site (normal response), Hypoglycemia (less pronounced than IGF-1 DES but present), Very short half-life means side effects are brief, Potential overuse injury if post-workout injection is used consistently without adequate recovery |
| Cited sources | 2 references | 3 references |
Key differences
- Evidence level differs: Ghrelin is investigational (in trials), while MGF is preclinical only.
- Administration: Ghrelin — Intravenous (research), Subcutaneous injection; MGF — Intramuscular injection (into worked muscle — critical for local effect), Subcutaneous injection (produces more systemic distribution).
- Dosing units differ: Ghrelin is dosed in mcg/kg, MGF in mcg — they operate at different scales.
- Frequency: Ghrelin is typically IV or SC bolus; endogenous levels peak pre-meal; MGF is Post-workout (within 30–60 minutes of training), 3–4x weekly.
- Research depth: this profile cites 2 sources for Ghrelin vs 3 for MGF.
How each works
Ghrelin
Ghrelin was discovered in 1999 as the endogenous ligand for the GHS-R1a receptor. Its acylated form activates GH release from the pituitary, stimulates appetite via NPY/AgRP hypothalamic neurons, and modulates energy homeostasis and fat storage. The des-acyl form (majority of circulating ghrelin) lacks GHS-R1a activity but has independent cardiovascular and cellular effects.
MGF
MGF is encoded by the IGF-1 gene but produced via alternative splicing that generates a unique 49-amino acid C-terminal E-peptide (Ec peptide). The Ec peptide has distinct biological activity from the IGF-1 domain — it directly activates satellite cell proliferation through a receptor pathway separate from the standard IGF-1R. Studies in rodents show that local MGF injection produces significant muscle hypertrophy in the injected limb without systemic IGF-1 elevation. MGF expression spikes within 30 minutes of resistance exercise and declines over 24–48 hours — aligning precisely with the post-exercise anabolic window.
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.