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GH SecretagogueSubcutaneous
Follistatin-315
Also known as: FST-315 · FS-315 · Circulating Follistatin
Longer isoform of follistatin — the major circulating form. Binds and inhibits myostatin and activin A like FST-344 but lacks the heparin-binding domain, so it circulates rather than binding to cell surfaces. Different pharmacokinetic profile but same downstream muscle-growth effect.
At a glance
- Half-life
- 24 hours
- Common route
- Subcutaneous
- Typical dose range
- 100–300mcg
- Stability (reconstituted)
- 14days refrigerated
Best timing
Daily or every other day in 10-day cycles. Comparative human data versus FST-344 is limited.
Contraindications
- Active cancer
- Pregnancy
- Cardiac disease (myostatin regulates cardiomyocyte mass)
- Limited human safety data
Watch symptoms
- Injection site reactions
- Tendon strain risk if muscle hypertrophy outpaces connective tissue
- Theoretical cardiac hypertrophy
- Limited human pharmacokinetic data
Citations