What it is
Follistatin is an activin-binding protein that neutralizes myostatin (GDF-8), a negative regulator of muscle growth. By sequestering activin and myostatin, follistatin shifts the balance toward muscle hypertrophy. It exists in three isoforms (FST-288, FST-315, FST-344) that differ in heparin-binding and cellular localization.
Evidence boundary
Preclinical and early-phase research only. Gene-therapy follistatin (a single administration) is a different modality from the recombinant peptide and is not a research-vial protocol.
Trial evidence
- Recombinant follistatin protein has been studied in preclinical muscle-hypertrophy models; gene-therapy forms are in early human trials for muscle-wasting indications.
Preparation and measurement
Reconstitution: 1 mg vial + 1 mL BAC = 1 mg/mL.
Concentration matches.
Reference schedule
| Phase | Dose | Draw / measure | Frequency | Weekly total |
|---|---|---|---|---|
| Conservative start | 100 mcg | 10 U (0.1 mL) | Once daily | 0.7 mg/week |
| Standard research | 200 mcg | 20 U (0.2 mL) | Once daily | 1.4 mg/week |
Conservative start
- Dose
- 100 mcg
- Draw / measure
- 10 U (0.1 mL)
- Frequency
- Once daily
- Weekly total
- 0.7 mg/week
Standard research
- Dose
- 200 mcg
- Draw / measure
- 20 U (0.2 mL)
- Frequency
- Once daily
- Weekly total
- 1.4 mg/week
Weekly totals apply only during the active phase.
Titration rules
- Recombinant protein range: 100–200 mcg SC daily for 10–30 day cycles.
- Cycles commonly run 10–30 days with a break of similar length.
- Shorter cycles, longer breaks — follistatin’s hypertrophic signal is slow to appear and persistent.
- Do not confuse with gene-therapy protocols (single administration, 6 × 10^11 vg/kg per leg) — those are experimental gene therapy, not a peptide vial.