Follistatin 315 vs SS-31 (Elamipretide)
Side-by-side comparison of key properties, dosing, and research.
Anabolic & IGF
Follistatin 315Anti-Aging & Longevity
SS-31 (Elamipretide)- Summary
- Follistatin 315 is a splice variant isoform of follistatin produced by alternative mRNA processing. Unlike Follistatin 344 which is tethered to cell surfaces via heparan sulfate proteoglycans, FST-315 circulates freely in the bloodstream and has broader systemic distribution. It is the predominant circulating form and exerts systemic myostatin inhibition as well as FSH suppression, making it relevant to both muscle growth and reproductive endocrinology.
- SS-31 (Elamipretide) is a synthetic mitochondria-targeting tetrapeptide that concentrates in the inner mitochondrial membrane and protects cardiolipin from oxidative damage. It is one of the most promising mitochondrial longevity compounds, studied in clinical trials for heart failure, renal disease, and age-associated mitochondrial dysfunction.
- Half-Life
- ~3–5 hours (longer systemic circulation vs FST-344)
- ~2–5 hours
- Admin Route
- SubQ, IM
- SubQ
- Research
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- Typical Dose
- No established human dosing protocol
- 5–10 mg
- Frequency
- Research use only
- Daily to several times per week
- Key Benefits
- Systemic myostatin inhibition for whole-body muscle growth
- Freely circulating — broader tissue distribution than FST-344
- Strong FSH-suppressive activity useful in certain hormonal protocols
- Potential for greater anabolic effect across multiple muscle groups simultaneously
- May be more relevant to reproductive endocrinology applications
- Studied in gene therapy approaches for muscular dystrophy
- Restores mitochondrial function and ATP production
- Protects inner mitochondrial membrane cardiolipin
- Reduces mitochondrial reactive oxygen species (ROS)
- Improves exercise capacity and reduces fatigue
- Cardioprotective — studied in heart failure trials
- Renoprotective — reduces ischemic kidney injury
- Anti-aging via mitochondrial preservation
- Potential in neurodegenerative disease prevention
- Side Effects
- Systemic FSH suppression — significant concern for fertility
- Greater potential for off-target effects vs FST-344 due to systemic distribution
- Limited human safety data
- Potential cardiac hypertrophy with prolonged high-dose exposure
- Injection site irritation
- Nausea (rare)
- Generally well-tolerated in clinical trials
- Stacks With
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