Follistatin 315 vs Sermorelin
Side-by-side comparison of key properties, dosing, and research.
Anabolic & IGF
Follistatin 315Growth Hormone PeptidesAnti-Aging & Longevity
Sermorelin- 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.
- Sermorelin is a bioidentical synthetic peptide comprising the first 29 amino acids of naturally occurring GHRH. It is FDA-approved for diagnostic use and widely prescribed off-label for anti-aging, stimulating growth hormone production in a natural pulsatile pattern that mimics the body's own rhythm.
- Half-Life
- ~3–5 hours (longer systemic circulation vs FST-344)
- 10–20 minutes
- Admin Route
- SubQ, IM
- SubQ
- Research
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- Typical Dose
- No established human dosing protocol
- 200–500 mcg
- Frequency
- Research use only
- 5–7 days 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
- Increases energy and vitality
- Improves body composition (more muscle, less fat)
- Enhances skin thickness and elasticity
- Strengthens immune system
- Improves sleep quality and REM sleep
- Supports bone density
- Enhances mental clarity and focus
- Safer than exogenous HGH — respects natural feedback loops
- FDA-approved for GH diagnostic use
- 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
- Flushing
- Headache
- Dizziness
- +2 more
- Stacks With
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