Follistatin 344 vs MK-677 (Ibutamoren)
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.
Follistatin 344
Follistatin 344 is a 344-amino acid isoform of follistatin — an endogenous glycoprotein that functions primarily as a myostatin and activin inhibitor. Myostatin (GDF-8) is the body's primary muscle growth suppressor; follistatin binds and neutralizes it with high affinity, removing this brake on muscle protein synthesis. Research and animal data show dramatic increases in muscle fiber size and strength when follistatin is elevated or myostatin is inhibited.
Full profileMK-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 profile| Follistatin 344 | MK-677 (Ibutamoren) | |
|---|---|---|
| Category | Performance & Growth Hormone | Performance & Growth Hormone |
| Also known as | FST-344, Follistatin isoform 344, FST | Ibutamoren, Nutrobal, MK677, L-163,191 |
| Evidence | Research-stage | Research-stage |
| Dosing range | 50mcg–200mcg mcg, Once daily or every other day for 10–30 day cycles | 10mg–50mg mg, once daily oral |
| Administration | Subcutaneous injection, Intramuscular injection (into target muscle — local effect hypothesis) | Oral (capsule/liquid) |
| Key side effects | Potential FSH suppression (reproductive effects in females — may affect menstrual cycle), Accelerated hair follicle cycling (Wnt pathway involvement — theoretical hair loss concern at high doses), Joint discomfort with rapid muscle tissue growth, Limited long-term human safety data | Water retention, Increased appetite, Elevated fasting glucose (long-term), Fatigue (initial, transient) |
| Cited sources | 3 references | 2 references |
Key differences
- Administration: Follistatin 344 — Subcutaneous injection, Intramuscular injection (into target muscle — local effect hypothesis); MK-677 (Ibutamoren) — Oral (capsule/liquid).
- Dosing units differ: Follistatin 344 is dosed in mcg, MK-677 (Ibutamoren) in mg — they operate at different scales.
- Frequency: Follistatin 344 is typically Once daily or every other day for 10–30 day cycles; MK-677 (Ibutamoren) is once daily oral.
- Research depth: this profile cites 3 sources for Follistatin 344 vs 2 for MK-677 (Ibutamoren).
How each works
Follistatin 344
Follistatin's muscle effects were dramatically illustrated when mice and cattle with follistatin overexpression or myostatin knockouts developed 2–3x normal muscle mass. Human follistatin gene therapy trials (AAV-mediated) are ongoing for Becker Muscular Dystrophy, showing sustained myostatin inhibition and improved muscle function over years from a single injection. Follistatin also inhibits activin A and B (involved in muscle wasting during illness), FSH secretion (reproductive effects), and inflammatory cytokines. The 344 isoform has an extended heparin-binding domain that increases tissue retention compared to the shorter FST-288 isoform.
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.
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.