Side-by-side · Research reference
Follistatin-344vsPEG-MGF
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
AHuman-MechanisticHUMAN-REVIEWED4/58 cited
BAnimal-MechanisticHUMAN-REVIEWED2/69 cited
Follistatin-344
Myostatin/Activin Antagonist · Research Use
15–25%FST/MSTN ratio ↑
344 AACirculating isoform
ResearchPhase status
Research · No approved protocol
PEG-MGF
IGF-1Ec Splice Variant · PEGylated
~2 hrHalf-life (PEG)
~7 minNative MGF t½
IGF-1EcSplice variant
SQ · Research Protocol
01Mechanism of Action
Parameter
Follistatin-344
PEG-MGF
Primary target
Myostatin (MSTN/GDF-8) and Activin A
IGF-1 receptor on muscle satellite cells and myocytes
Pathway
FST-344 binds MSTN/Activin → prevents ActRIIB receptor engagement → disinhibits muscle anabolism
IGF-1R → PI3K/Akt → mTOR activation → Satellite cell proliferation & myoblast fusion
Downstream effect
Elevated follistatin/myostatin ratio, increased muscle protein synthesis, attenuated muscle atrophy signalingJeong 2026
Satellite cell activation, muscle fiber repair, localized hypertrophy signaling
Feedback intact?
Yes — indirect antagonist, preserves endogenous regulation
Partially bypassed — does not require hepatic IGF-1 synthesis
Origin
Endogenous glycoprotein, 344-AA isoform lacking heparin-binding domain (vs FST-315)
IGF-1Ec splice variant (exon 4–6) conjugated to polyethylene glycol for extended circulation
Antibody development
Not documented in available trials (endogenous protein)
Unknown — no long-term human immunogenicity data
02Dosage Protocols
Parameter
Follistatin-344
PEG-MGF
Clinical protocol
None — no approved dosing regimen
Follistatin-344 measured as endogenous biomarker, not administered exogenously in cited trials.
—
Research context
Endogenous modulation via exercise + nutrition
Resistance training + EAA intake elevated FST/MSTN ratio by 15–25% in 12-week RCT (older women).
—
Evidence basis
Human observational / biomarker studies
Animal / mechanistic
Half-life
Not established
Circulating isoform; lacks tissue-binding domain of FST-315.
~2 hours (PEGylated)
Native MGF: ~7 min; PEGylation extends circulation.
Research dose range
—
100–200 mcg
Extrapolated from animal models; no validated human protocols.
Frequency
—
Post-training or daily
Timing to match endogenous MGF pulse post-exercise.
Reconstitution
—
Sterile bacteriostatic water
Lyophilized form; store reconstituted at 2–8 °C.
PEG molecular weight
—
Typically 5–30 kDa
Higher MW = longer t½, greater steric hindrance.
Timing
—
Within 30–60 min post-training
Aligns with endogenous MGF window.
03Metabolic / Fat Loss Evidence
Parameter
Follistatin-344
PEG-MGF
Primary target
Muscle mass preservation, not direct lipolysis
Muscle tissue (satellite cells, myocytes) — not adipose-specific
Indirect fat effect
Increased lean mass → elevated resting metabolic rate
Not primary mechanism. Muscle-sparing during deficit.
—
Clinical evidence
Lorcaserin trial (6 mo) showed no MAFI axis changes during fat lossRamirez-Cisneros 2026
Suggests follistatin not primary driver of fat loss in weight-reduction interventions.
—
GLP-1RA studies
Liraglutide (35 days) — no significant MAFI axis modulation despite fat/lean changes
—
Indirect metabolic effect
—
IGF-1 signaling may modulate insulin sensitivity and lipid metabolismRen 2015
Mechanism distinct from direct lipolytic peptides.
Body composition
—
Lean mass preservation / hypertrophy focus
Fat loss evidence
—
No direct human or animal RCT data for PEG-MGF-driven fat reduction
04Side Effects & Safety
Parameter
Follistatin-344
PEG-MGF
Clinical safety data
None — no human exogenous administration trials in literature
—
Theoretical risks
Excessive myostatin inhibition → muscle overgrowth, impaired glucose tolerance
Based on myostatin-null animal models and clinical myostatin inhibitor trials.
—
Endogenous elevation (exercise)
No adverse effects reported in 12-week resistance + EAA trials
—
Cancer risk (theoretical)
Myostatin inhibition may promote tumor growth in malignancy (preclinical data)
—
Regulatory status
Not approved for human use — research peptide only
—
Injection site reaction
—
Erythema, induration (common with SQ peptides)
Hypoglycemia risk
—
IGF-1 axis activation can lower blood glucose
IGF-1R overstimulation
—
Theoretical risk of aberrant cell proliferation with chronic supraphysiological exposure
Fluid retention
—
Possible with IGF-1 pathway activation (dose-dependent)
PEG accumulation
—
Chronic high-dose PEGylated proteins may accumulate in tissues; clearance slower in renal impairment
Antibody formation
—
PEGylated proteins can elicit anti-PEG antibodies (neutralizing potential unknown)
Cancer risk
—
IGF-1 axis stimulation contraindicated in active malignancy
Human safety data
—
Absent — no published human trials for PEG-MGF
Absolute Contraindications
Follistatin-344
- ·Active malignancy
- ·No approved protocol — research use only
PEG-MGF
- ·Active malignancy or history of cancer (IGF-1R proliferative signaling)
- ·Known hypersensitivity to PEGylated compounds
- ·Pregnancy / lactation (no reproductive toxicity data)
Relative Contraindications
Follistatin-344
- ·Insulin resistance / Type 2 diabetes (monitor glucose)
- ·Pregnancy / lactation (unknown safety profile)
PEG-MGF
- ·Diabetes (monitor glucose closely)
- ·Renal impairment (PEG clearance reduced)
- ·Retinopathy (IGF-1 axis effects on vascular proliferation)
05Administration Protocol
Parameter
Follistatin-344
PEG-MGF
1. Regulatory status
Follistatin-344 is not approved for human administration. All cited studies measure endogenous serum follistatin as a biomarker, not as an exogenous therapeutic agent.
Add 1–2 mL bacteriostatic water to lyophilized vial. Swirl gently — do not shake. Solution should be clear to slightly opalescent.
2. Endogenous modulation
Resistance exercise combined with essential amino acid (EAA) supplementation elevated the follistatin/myostatin ratio by 15–25% in 12-week randomized trials. Protein intake (1.2–1.5 g/kg/day) synergizes with training to upregulate endogenous follistatin.
Subcutaneous — abdomen or thigh. Rotate sites to avoid lipodystrophy. Avoid areas with scar tissue or active inflammation.
3. Measurement context
Serum follistatin and follistatin/myostatin ratio are used diagnostically in sarcopenia screening and as biomarkers of muscle anabolic balance in clinical trials.
Post-training preferred (within 30–60 min) to align with endogenous MGF expression window. Alternatively, daily morning dose on non-training days.
4. Research consideration
Gene therapy and recombinant follistatin delivery are under preclinical investigation for muscular dystrophy and sarcopenia. No human safety or efficacy data for exogenous FST-344 administration.
Lyophilized: room temperature, light-protected, desiccated. Reconstituted: refrigerate 2–8 °C, use within 14–21 days.
5. Needle
—
29–31G insulin syringe, 8–12 mm length. Pinch skin fold, insert at 45° angle for subcutaneous delivery.
06Stack Synergy
Follistatin-344
+ BPC-157
Multi-pathwayFollistatin-344 (myostatin antagonist) and BPC-157 (tissue repair peptide) address complementary pathways in muscle recovery. FST-344 promotes muscle protein synthesis by disinhibiting myostatin signaling, while BPC-157 accelerates healing of tendons, ligaments, and microtears via angiogenesis and collagen synthesis. Combined, they may support both hypertrophy and structural repair during high-volume training or injury recovery.
- Follistatin-344
- No approved protocol — endogenous modulation via resistance exercise + EAA
- BPC-157
- 250–500 mcg SQ · twice daily · near injury site or systemic
- Duration
- 4–8 weeks
- Primary benefit
- Muscle hypertrophy + accelerated soft tissue repair
+ TB-500
ModerateTB-500 (thymosin beta-4 fragment) promotes cell migration, angiogenesis, and anti-inflammatory signaling in muscle and connective tissue. Follistatin-344's anabolic signaling may synergize with TB-500's regenerative effects during muscle damage or overtraining, particularly in older adults where both myostatin inhibition and tissue repair are rate-limiting.
- Follistatin-344
- Endogenous upregulation (resistance training + protein)
- TB-500
- 2–5 mg SQ · twice weekly · loading phase 4 weeks, then maintenance
- Frequency
- Twice weekly TB-500, daily training stimulus for FST
- Primary benefit
- Enhanced recovery, reduced inflammation, muscle growth support
PEG-MGF
+ BPC-157
ModerateBPC-157 promotes angiogenesis and tendon/ligament repair via VEGF and growth factor modulation, while PEG-MGF targets satellite cell activation and myocyte proliferation. Complementary pathways for comprehensive tissue repair post-injury or intensive training. BPC-157's systemic stability and oral bioavailability contrast with PEG-MGF's localized IGF-1R signaling.
- PEG-MGF
- 100–200 mcg SQ post-training
- BPC-157
- 250–500 mcg SQ or oral, twice daily
- Duration
- 4–6 weeks (injury-dependent)
- Primary benefit
- Accelerated muscle and connective tissue repair, enhanced recovery
+ TB-500
StrongTB-500 (Thymosin Beta-4 fragment) upregulates actin polymerization, cell migration, and anti-inflammatory pathways, while PEG-MGF drives satellite cell proliferation via IGF-1R/mTOR. Synergistic for muscle regeneration: TB-500 mobilizes progenitor cells, PEG-MGF stimulates their differentiation into myocytes. Both have overlapping but distinct repair cascades.
- PEG-MGF
- 100–200 mcg SQ post-training
- TB-500
- 2–5 mg SQ, 2× per week (loading), then weekly
- Timing
- Stagger injections by 6–12 hours
- Primary benefit
- Maximal satellite cell recruitment and myogenic differentiation, injury repair