Follistatin vs P21
Side-by-side comparison of key properties, dosing, and research.
Anabolic & IGF
FollistatinCognitive EnhancementAnti-Aging & Longevity
P21- Summary
- Follistatin is an endogenous glycoprotein that acts as a potent inhibitor of myostatin and activin, two proteins that limit muscle growth. By binding and neutralizing myostatin, follistatin removes the primary brake on skeletal muscle hypertrophy, enabling significant muscle growth beyond normal physiological limits. It is distinct from its isoforms Follistatin 315 and Follistatin 344 in tissue distribution and binding affinity.
- P21 is a synthetic peptide derived from CNTF (ciliary neurotrophic factor) that promotes hippocampal neurogenesis, enhances memory and spatial learning, and may reduce amyloid-beta pathology. It is used as a neurogenic and cognitive enhancer with potential anti-Alzheimer's applications.
- Half-Life
- ~3–5 hours (endogenous form)
- Not well characterized; likely short, but neurogenic effects persist long after administration
- Admin Route
- IM, SubQ
- SubQ, Intranasal
- Research
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- Typical Dose
- 50–100 mcg per injection site
- 100–500 mcg
- Frequency
- Every other day or 2–3x per week
- Once daily
- Key Benefits
- Potent myostatin inhibition enabling supraphysiological muscle growth
- Increases skeletal muscle mass and fiber size
- May accelerate recovery from muscle injury
- Potential benefits in muscular dystrophy and sarcopenia
- Synergistic with IGF-1 and growth hormone in anabolic protocols
- Animal studies show dramatic increases in muscle mass
- Reduces muscle fibrosis in dystrophic models
- Promotes hippocampal neurogenesis
- Enhances spatial memory and learning
- Increases BDNF expression
- Reduces amyloid-beta plaque formation (animal models)
- Anti-tau pathology potential
- Cognitive enhancement without stimulant effects
- Potential therapeutic for Alzheimer's and cognitive aging
- Side Effects
- Potential for excessive muscle growth if doses are not controlled
- FSH suppression with implications for fertility in women
- Theoretical risk of cardiac hypertrophy with prolonged high-dose use
- Limited human safety data available
- +1 more
- Generally well tolerated in animal studies
- Limited human clinical data
- Injection site reactions
- Potential mild fatigue at initiation
- Stacks With
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