This page describes pharmacological agents that may have legal restrictions, side effects, and drug interactions in your jurisdiction. Information is for educational research only — consult a clinician before considering any compound.

High-risk compound

Surface here is educational only; do not use without medical supervision. Our editorial verdict is SKIP-FOR-NOW — current cost / risk / redundancy puts it below the line.

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Follistatin

Emerging Research

Myostatin Inhibitor | TGF-β Antagonist for Muscle Research

Aliases (6)

FST · FST-344 · FST-315 · ACE-083 · ACE-031 · FS344

TYPICAL DOSE

100-200 mcg (anecdotal only)

Daily

ROUTE

Subcutaneous injection

Subcutaneous / IM

CYCLE

10-30 days

Typical duration

STORAGE

-20°C (lyophilized)

Refrigerated

Overview

What is Follistatin?

Follistatin is an endogenous glycoprotein and potent myostatin inhibitor produced in many tissues. As a research peptide (often follistatin-344), it is investigated and used off-label for muscle growth and tissue regeneration.

Key Benefits

Reported muscle hypertrophy beyond natural genetic ceiling, fat loss, recovery enhancement, and joint repair. Used off-label by physique athletes. Distinct from anabolic steroids — works through myostatin pathway.

Mechanism of Action

Binds and neutralizes myostatin (GDF-8) and activin, removing the negative regulator of muscle growth. Loss of myostatin signaling allows uncontrolled muscle satellite cell proliferation and hypertrophy.

▸ Reconstitution Lyophilized peptide

Reconstitute lyophilized peptide with bacteriostatic water (BAC) using sterile technique. Calculator below converts vial mg + diluent mL into syringe units.

Steps

1 Wipe BAC water vial + peptide vial stoppers with isopropyl alcohol.
2 Draw the planned diluent volume into a 1 mL syringe.
3 Inject diluent slowly down the inside wall of the peptide vial — do NOT spray onto powder.
4 Swirl gently (do not shake) until fully dissolved. Solution should be clear.
5 Label vial with date reconstituted; refrigerate 2-8 °C.
6 Use within 30 days for most peptides (BPC-157 / TB-500 ~ 60 days at 4 °C).

Open dose calculator for Follistatin

Research Indications

Most Effective

Myostatin (GDF-8)

the muscle-mass negative regulator. Knockout myostatin mice ("Schwarzenegger mice"), Belgian Blue cattle, and the documented German hyper…

Effective

Activin A

broader TGF-β superfamily ligand involved in muscle, gonadal function (FSH regulation, ovarian folliculogenesis, spermatogenesis), and in…

Peptide Interactions

Other anabolic agents (AAS, SARMs, GH, IGF-1, MK-677):

Avoid

Compound cardiac hypertrophy risk, compound tendon-mismatch risk, compound HPG suppression.

ARBs/ACE inhibitors:

Avoid

Theoretical interaction via shared cardiac remodeling pathways — no human data but caution flag.

IGF-1 LR3

Compatible

Both promote muscle growth through different pathways. Theoretical synergy but no studies on combination. Increased anabolic signaling may compound risks.

BPC-157

Compatible

Different mechanisms - BPC-157 promotes tissue repair while follistatin inhibits growth suppressors. No interaction data available.

TB-500

Compatible

Both involved in tissue regeneration through different pathways. No published studies on combination effects.

CJC-1295

Compatible

Some protocols combine follistatin with GH secretagogues. Different mechanisms but no safety data on combinations.

HGH

Monitor

Both promote anabolic effects. Theoretical additive muscle growth but combined use increases risk of excessive growth factor stimulation. No clinical data.

Testosterone/Androgens

Monitor

Androgens increase muscle mass through androgen receptors while follistatin inhibits myostatin. Combined use studied in some animal models but human data lacking.

ACE-031

Avoid

Both target myostatin pathway. ACE-031 was discontinued due to vascular side effects. Combining myostatin inhibitors may increase adverse event risk.

Other Myostatin Inhibitors

Avoid

Stacking multiple myostatin inhibitors provides no proven benefit and may increase risk of off-target TGF-β pathway disruption.

Quality Indicators

Extremely limited human peptide data

Most research involves gene therapy, not injectable peptide

Very short half-life (~90 minutes)

Native follistatin rapidly cleared from circulation

WADA banned substance

Prohibited in sports since 2019

✗

Excessive dosing risk

Vision impairment reported at 10x dose. Never exceed 200mcg/day

What to Expect

Day 1-7
Injection / administration protocol established. Tolerability check.
Week 2-4
Early onset of effect — subtle in most users, noticeable in responders.
Week 4-8
Peak benefit window for most peptide cycles.
Week 8+
Cycle decision point: continue, taper, or break.

Side Effects & Safety

Common (>10% in clinical trials): Nosebleeds, telangiectasias (skin spider veins), injection-site reactions for local delivery, transient muscle pain.
Less common (1-10%): Headache, fatigue, GI upset, joint pain.
Rare-serious (<1% but worth knowing):
- Cardiac hypertrophy concern — animal data suggests ActRIIB pathway blockade can drive pathological cardiac hypertrophy (the heart is muscle and responds to myostatin signaling). This was not definitively demonstrated in human trials but it's why the FDA + Acceleron program chose narrow indications.
- Vascular endothelial concerns — telangiectasias and nosebleeds suggest off-target action on vascular bed, possibly via BMP9/10 pathway interaction. Unknown long-term implications.
- Reproductive axis disruption — activin A regulates FSH secretion; chronic activin neutralization could theoretically suppress FSH → impaired spermatogenesis (males) or anovulation (females). Animal data shows this; human trials weren't long enough to rule it out.
- Tendon/connective-tissue mismatch — rapid muscle hypertrophy without proportional tendon adaptation = tear/strain risk. Documented in myostatin-knockout animal models.
Specific watch periods: First 4 weeks (vascular/nosebleed signal would emerge), 12 weeks (cardiac echo if used), 6 months (gonadal axis labs).