Follistatin
FLGR242, modified follistatin fragment
Follistatin (FLGR242, modified follistatin fragment) is a gh & growth research compound. Follistatin binds and neutralises myostatin, the brake on muscle growth. Full-length follistatin also binds ACTIVIN, and activin blockade is where several myostatin-pathway drug programmes ran into vascular and bleeding side effects. FLGR242 is sold as a fragment engineered NOT to bind activin — the intent being myostatin inhibition without the activin liability.
Follistatin quick facts
| Reported research dose | 100-300mcg per administration |
| Route | Subcutaneous |
| Frequency | Undefined |
| Half-life | Unpublished for this construct |
| Forms | Injectable |
| Evidence level | Theoretical — no published trial of this construct in any species |
**This is not Follistatin 344 and should not be dosed as if it were** — the Vault carries that separately. The selectivity claim is the entire premise of the molecule and it comes from the manufacturer, not from a published paper. Worth knowing before anyone reasons from FST-344 data.
How Follistatin works
Follistatin binds and neutralises myostatin, the brake on muscle growth. Full-length follistatin also binds ACTIVIN, and activin blockade is where several myostatin-pathway drug programmes ran into vascular and bleeding side effects. FLGR242 is sold as a fragment engineered NOT to bind activin — the intent being myostatin inhibition without the activin liability.
Proposed benefits
Myostatin inhibition for muscle growth, engineered to skip the activin blockade that derailed earlier drugs in this class.
Human clinical evidence
- No completed randomised human trials, but this is a compound where that is a statement about the calendar rather than about the molecule — human work is underway and the position may change.
📊 Correlative data
- Follistatin biology in humans comes almost entirely from the full-length protein and from gene-therapy work, not from this construct. A small follistatin gene-therapy study in Becker muscular dystrophy reported improved walking distance in a handful of patients — an uncontrolled trial, a different molecule, and a different delivery route.
- Do not import Follistatin 344 data onto this. The Vault carries FST-344 separately for exactly that reason.
🧪 How the mechanism reads
- Myostatin restrains muscle growth; follistatin binds and neutralises it. Humans and cattle with loss-of-function myostatin mutations are visibly, heritably more muscular, so the target is real and the direction is not in doubt.
- The selling point of this construct is what it does NOT bind. Full-length follistatin also neutralises activin, and activin blockade is where several pharmaceutical myostatin programmes ran into trouble — including bleeding and vascular events that ended at least one late-stage programme. A fragment that spares activin would, in principle, keep the muscle effect and drop that liability.
- That selectivity claim originates with the manufacturer. There is no published characterisation of FLGR242's binding profile, potency, or half-life to check it against — so the central premise of the molecule is currently an assertion, not a finding.
These tiers tell you how much human evidence exists — not how well something works. This is the research space, and most of what’s in here is new rather than disproven. Something sitting at “theoretical” usually means nobody has funded the trial, not that the trial was run and failed.
The trap runs the other way too: something can be clinically validated and still do very little for you specifically. A statistically significant result in a study population is not a promise about your body.
- ✅ Clinically validated — human randomised trials or meta-analyses support it. The strongest footing available.
- 📊 Correlative — observational or epidemiological data. Suggestive, and genuinely useful for direction, but it cannot establish cause.
- 🧪 Theoretical / mechanistic — the mechanism is understood and often demonstrated in cells or animals, and the human trial doesn’t exist yet. Unproven is not the same as ineffective. Plenty of what’s standard practice today sat here five years ago.
✗ is a safety flag, not a grade. Where you see it, the concern is harm — not a disappointing trial. A compound tested for one purpose and found not to help there can still be worth studying somewhere else, so a negative result never gets rendered as a cross. It sits alongside the tier, because something can be both well-studied and genuinely risky.
My job is to tell you which one you’re looking at, and let you make the call. Grading something low isn’t me dismissing it — it’s me refusing to oversell it. This is the research space, and being able to reason forward from a mechanism matters as much as waiting for the trial.
Follistatin — safety, predicted from mechanism
Much of this compound class has never been through a human safety trial. Rather than say nothing — or print a generic warning — this is what its known mechanism predicts could go wrong, and what you can do about it. Predictions are labelled as predictions.
What the mechanism predicts
Derived from what this molecule does, not from a trial.
- These inhibit myostatin or activin signalling — the brake on muscle growth. Removing a brake the body installed deliberately is the whole premise, and the predicted problems follow from that.
- Myostatin and activin are not muscle-only signals. The same TGF-β family regulates tendon and connective tissue, and the concern that follows is muscle gaining force capacity faster than tendon adapts — predicting tendon and joint injury rather than muscle injury.
- Activin signalling also has roles in reproduction and inflammation, so systemic inhibition has predicted consequences well beyond the muscle the user is aiming at.
What has actually been reported
- Trials of myostatin-pathway drugs have repeatedly shown the dissociation that matters: muscle mass increases without a proportional increase in strength or function. That result recurs across programmes and is the main reason several were discontinued.
- Bimagrumab produced muscle gain and fat loss in trials alongside diarrhoea and muscle spasms.
- YK-11 has no human trial data at all. It is frequently described as a myostatin inhibitor on the strength of a single cell-culture study.
How to reduce the risk
Each of these follows from the same mechanism as the prediction.
- If tendon lags muscle, the answer is loading tendon deliberately — slow heavy resistance work — and not adding load as fast as the new muscle allows.
- Treat rapid strength gain as a reason to be more conservative with progression, not less.
What it does to your bloodwork
A fact about the assay, not a guess about the drug.
- Liver function, especially for the oral compounds in this group. Creatine kinase if you are getting unusual soreness or spasm.
Don't run this if
- You have a history of tendon injury, or you are progressing loading aggressively already.
The honest unknown
- Almost everything. No compound in this group has established long-term human safety, and the consistent trial finding is that mass gained this way has not translated into function.
Not medical advice. If you take prescription medication or have a diagnosed condition, check this with a pharmacist or doctor.
Where to get Follistatin
Buy Follistatin at Biolongevity Labs →Follistatin — interference & stacking
Predicted from mechanism, not from an interaction study. There are no trials of these combinations — what follows is what the biology implies, so treat it as a reason to watch something, not as a finding.
What Follistatin moves on your bloodwork
These are the markers this compound is expected to move, and which direction. Knowing that in advance is mostly about NOT panicking: some of these moving is the compound working.
- IGF-1 (Insulin-like Growth Factor 1) — ↑ expected to rise
This is the point. IGF-1 rising is the compound doing its job — it is the stable downstream readout of a GH pulse.
What to do: Test it before you start and again at 6–8 weeks. It is the only number that tells you whether the product was real and the dose was enough. - Growth Hormone, Serum — ✕ unreliable here
A random GH level is close to meaningless here. GH is secreted in pulses during deep sleep and sits undetectable between them, so a daytime draw catches a trough almost every time — including when the compound is working perfectly.
What to do: Do not use GH to judge a secretagogue. Read IGF-1 instead. - Fasting Insulin — ↑ expected to rise
GH is a counter-regulatory hormone: it opposes insulin. Fasting insulin and glucose drifting up is the predicted trade-off, not a surprise.
What to do: Check fasting insulin and HbA1c at baseline and again at 8–12 weeks. This is the marker that decides whether you keep running it. - HbA1c (Hemoglobin A1c) — ↑ expected to rise
Same mechanism, longer window — a slow drift rather than a jump.
What to do: Pair it with fasting insulin; either alone can mislead. - Free T4 (Thyroxine) — ↓ expected to fall
GH accelerates the peripheral conversion of T4 to T3, so free T4 can fall while free T3 holds or rises. Read alone it looks like new hypothyroidism, and it usually isn't.
What to do: Run a full thyroid panel rather than TSH alone before concluding anything.
- Which compounds push the same lever, and why the dose adds up faster than people count
- What blunts it — the stacks that waste your money
- What compounds the risk, so a side effect arrives sooner than any one of them suggests
- Coach Cam's read on running it alongside the rest of your protocol
Get the complete breakdown for Follistatin — inside the Academy alongside the full interactive Vault.
Unlock in the Academy — $10/mo →Everything above follows from one fact: these raise GH and therefore IGF-1. Nothing here needs a trial of the specific molecule.
- How to work up to it, and when not to
- When to take it, and why that window
- Cycle length
- Time off between cycles
- Fasted or fed, and when in the day
- Needle gauge and injection site
- Coach Cam's personal notes
Get the complete breakdown for Follistatin — inside the Academy alongside the full interactive Vault.
Unlock in the Academy — $10/mo →Bloodwork to run alongside Follistatin
Run these before you start, and again after 8–12 weeks. A baseline you didn’t take is one you can never go back for.
| Marker | What it’s watching for |
|---|---|
| IGF-1 (Insulin-like Growth Factor 1) | The number that actually tracks your GH exposure — dose by this, not by feel |
| Fasting Insulin | GH raises insulin resistance; this moves before glucose does |
| HbA1c (Hemoglobin A1c) | The slower confirmation that the insulin change is real |
| Comprehensive Metabolic Panel (CMP) | Fasting glucose, and liver and kidney at baseline |
The Running GH Peptides or MK-677 panel covers these in one order — 9 markers, $132.30 with the discount applied.
Check results you already have → · All 102 markers A–Z
Follistatin — frequently asked questions
What is Follistatin?
Follistatin (FLGR242, modified follistatin fragment) is a gh & growth research compound. Follistatin binds and neutralises myostatin, the brake on muscle growth. Full-length follistatin also binds ACTIVIN, and activin blockade is where several myostatin-pathway drug programmes ran into vascular and bleeding side effects. FLGR242 is sold as a fragment engineered NOT to bind activin — the intent being myostatin inhibition without the activin liability.
Is the full Follistatin protocol on this page?
The reported research dose is on this page, along with how Follistatin works and the evidence behind it. The protocol — how to work up to it, frequency, cycle length, time off, what not to stack it with and Coach Cam's notes — is inside the Academy.
What is the half-life of Follistatin?
Follistatin has an approximate half-life of Unpublished for this construct, which is part of what determines how often it's dosed.
What's the evidence behind Follistatin?
Current evidence level: Theoretical — no published trial of this construct in any species. Follistatin is offered for research purposes only and is not an approved medicine.
Want Coach Cam's exact Follistatin protocol?
Dosing schedules, stacking, cycle timing and my personal notes live inside the Academy — plus the full interactive Vault of 237 compounds & 350 supplements.
Join the Academy — $10/mo →