Follistatin 315 vs Thymalin
Side-by-side comparison of key properties, dosing, and research.
Anabolic & IGF
Follistatin 315Immune SupportAnti-Aging & Longevity
Thymalin- 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.
- Thymalin is a polypeptide complex isolated from calf thymus glands (developed by the Russian Gerontology Institute), shown to restore immune function, extend lifespan, and reverse thymic involution. Clinical studies demonstrate improved immune parameters and up to 40% reduction in mortality in elderly patients.
- Half-Life
- ~3–5 hours (longer systemic circulation vs FST-344)
- Not well characterized as a complex extract; individual peptides have varying kinetics
- Admin Route
- SubQ, IM
- SubQ, IM
- Research
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- Typical Dose
- No established human dosing protocol
- 10 mg IM or SC daily
- Frequency
- Research use only
- Once daily
- 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 thymic function and T-cell immunity
- Extends healthy lifespan (documented in long-term studies)
- Reduces infectious disease incidence in elderly
- Normalizes immune parameters in immunodeficiency
- Anti-tumor immune surveillance
- Improves vaccine response in elderly
- Reduces cardiovascular mortality (40% in landmark Russian study)
- Normalizes neuroendocrine function
- 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
- Very well tolerated in decades of Russian clinical use
- Mild injection site reactions
- Rare: mild allergic reaction (natural extract)
- Transient flu-like symptoms on initiation (immune activation)
- Stacks With
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