Follistatin: Side Effects & Safety

Part of the Follistatin Complete Guide

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Overall Safety Profile

Follistatin's safety profile for injectable research use is poorly characterized. Gene therapy studies (AAV-follistatin) in muscular dystrophy have shown a generally acceptable safety profile, but these use a fundamentally different delivery method. Injectable follistatin-344 lacks formal safety evaluation.

Potential Side Effects

  • Reproductive effects: Follistatin inhibits activin, which regulates FSH — reproductive hormone disruption is possible
  • Injection site reactions: Common with protein injections
  • Immune response: Possible antibody formation against exogenous protein

Critical Limitations

No clinical trials of injectable follistatin for muscle growth in healthy humans exist. Long-term effects of chronic myostatin inhibition are unknown. TGF-β signaling has complex, context-dependent roles in cancer — both tumor-suppressive and tumor-promoting. Myostatin also has roles in cardiac tissue.

Potential Contraindications

  • Active cancer (TGF-β pathway involvement)
  • Cardiac conditions (myostatin affects cardiac tissue)
  • Fertility concerns (activin/FSH disruption)
  • Pregnancy and breastfeeding

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Peptides Insider Editorial Team

Our content is reviewed for accuracy and grounded in peer-reviewed research where available. We do not provide medical advice. Always consult a qualified healthcare professional.