Follistatin 344: Benefits, Dosage & Side Effects

Jay Campbell

By Jay Campbell

December 1st, 2022


When I wrote about the best muscle-building peptides in existence, there were two peptides which I talked about but hesitated to make a recommendation on.

One of them was Follistatin 344, a peptide I had written about in an email many years ago but have forgotten about ever since.

But there’s been a renewed interest in this compound from my audience and in the underground fitness community as a whole.

However, what really piqued my attention was the growing focus on muscle wasting:

And if you know anything about building more muscle, it is the secret to fully optimized health and transcends vanity 100 times over.

Back to the main question at hand: I

s Follistatin 344 the muscle-building peptide we’ve been ignoring this entire time, or is it all bark and no bite?

Keep reading and you’ll get my definitive answer (for now).

What is Follistatin 344?

Follistatin 344 (a.k.a. FST344) is a naturally occurring peptide in your body whose initial discovery is far removed from anything to do with building muscle.

In fact, Follistatin comes in many forms within your body:

“Follistatin (FS) is a secreted glycoprotein, which is found in many tissues and organs (e.g. pituitary, bone marrow, ovary, kidney, liver, blood vessels)… Due to alternative splicing of the FS-gene, two main FS isoforms exist in humans, namely “FS315” (“FS344”) and “FS288” (“FS317”).

“FS315” and “FS288” refer to the total number of amino acids, the alternative names “FS344” and “FS317” to the last amino acid of the unprocessed protein, which consists of 344 amino acids. However, after translation the N-terminal signal peptide containing the first 29 amino acids is cleaved off. While FS315 is the main isoform circulating in blood, FS288 is mostly found in tissues”

Follistatin was first isolated in December 1987 from porcine ovarian follicular fluid and its discovery was significant due to its selective inhibition of follicle-stimulating hormone (FSH):

“The isolated molecule j(Mr 35,000) is highly enriched in cysteines and is composed of a single polypeptide chain. In addition, it has no sequence homology with the previously characterized follicular fluid inhibins, which are heterodimeric proteins of Mr 32,000 with follicle-stimulating hormone release-inhibiting activity.

This protein specifically inhibits the basal secretion of follicle-stimulating hormone, but not that of luteinizing hormone, in the rat anterior pituitary monolayer culture system with a half-maximal effective dose of 2.5-6.0 ng/mL”

It wasn’t until 2001 where the first probable link was made between follistatin and muscle growth through the inhibition of a compound known as myostatin (more on that later):

“Myostatin is a transforming growth factor-β family member that acts as a negative regulator of skeletal muscle mass. To identify possible myostatin inhibitors that may have applications for promoting muscle growth, we investigated the regulation of myostatin signaling…Binding of myostatin to Act RIIB could be inhibited by the activin-binding protein follistatin and, at higher concentrations, by the myostatin propeptide.

…we generated transgenic mice expressing high levels of the propeptide, follistatin, or a dominant-negative form of Act RIIB [activin type II receptors] by using a skeletal muscle-specific promoter. Independent transgenic mouse lines for each construct exhibited dramatic increases in muscle mass comparable to those seen in myostatin knockout mice. Our findings suggest that the propeptide, follistatin, or other molecules that block signaling through this pathway may be useful agents for enhancing muscle growth for both human therapeutic and agricultural applications.”

The idea is quite simple on the face of it: More follistatin = less myostatin = more muscle growth!

What Does Follastin 344 Do?

Follistatin 344 interacts with myostatin in several ways, all of which contribute to accelerated muscle growth:

“Follistatin has been shown to be capable of binding directly to myostatin and inhibiting its activity in receptor binding and reporter gene assays in vitro.

Moreover, follistatin also appears to be capable of blocking endogenous myostatin activity in vivo, as transgenic mice overexpressing follistatin specifically in skeletal muscle have been shown to exhibit dramatic increases in muscle growth comparable to those seen in Mstn-knockout mice.

Finally, mice homozygous for a targeted mutation in the Fst gene have reduced muscle mass at birth, consistent with a role for follistatin in inhibiting myostatin activity during embryonic development”

Myostatin’s role in building muscle was known as early as 1997, thanks to the pivotal discovery of scientist Se-Jin Lee:

“He had been identifying and characterizing new members of the TGF-β family of signaling proteins that he called growth/differentiation factors (GDFs) and had knocked out various GDFs in mice, including GDF8. “When we knocked it out, it turned out to have this hypermuscular phenotype,” says Lee

Lee renamed GDF8 “myostatin,” and over the next two decades his laboratory went on to elucidate how it works. Lee has even sent myostatin-knockout mice to the International Space Station to see how microgravity would affect them.

Lee’s work has shown that myostatin blocks muscle growth and its absence dramatically increases skeletal muscle mass. By targeting TGF-β signaling in muscles, Lee has generated mice that had four times more muscle mass than normal.

In addition, he reported the identification of naturally occurring myostatin mutations in double-muscled breeds of cattle, as well as in a heavily muscled child.”

If you’re thinking of those Internet memes with the ridiculously muscular cows, then you’ve already seen myostatin inhibition in action:

Belgian Blue - Cattle International Series

The most popular “double muscled” breed is known as the Belgian Blue, and these cows are very specifically bred for the purpose of being as muscular as possible:

Double-muscled cattle refers to breeds of cattle that carry one of seven known mutations that limits and reduces the activity of the myostatin protein.

Normally, myostatin limits the number of muscle fibers present at birth, and interfering with activity of this protein causes animals to be born with higher numbers of muscle fibers, consequently augmenting muscle growth. Additionally, these mutations reduce the superficial and internal fat deposits, causing the meat to be less marbled and lower in fat content.

Animals homozygous for myostatin mutation (inheriting a mutant copy of myostatin from both sire and dam) also have improved meat tenderness in some cuts of meat. The enlarged muscles of dam and calf at birth leads to increased difficulty of calving, and in some breeds frequently necessitates birth by cesarean section.”

As with everything else in life, there are tradeoffs:

Some of the risks faced by double-muscled cows include higher susceptibility to respiratory illnesses and thinner/shorter bones.

Let’s see if these laboratory observations can be applied to the real world.

Follistatin 344 Benefits: Muscle, Muscle, and More Muscle!

While there may be some fringe benefits of Follistatin 344 use, nothing has been more extensively studied and profiled more than its connection to building inhuman levels of lean muscle mass.

So with whatever evidence is available to us, I’m going to divide it into three separate groups…

Biohacker Testimonials

These are all the brave anonymous souls who tried to procure Follistatin 344 through the black/grey market and try the peptide on themselves.

I can’t put every testimonial on the Internet here, but have a look at some of the more transformative ones.

Reddit user luciferjk: “I had gained a pound and a half this morning and I looked leaner. Probably too soon to say, but their follistatin seems to be real, I’ve felt flu like symptoms just like you’d expect with tagged follistatin, and the effect on my muscles is PROFOUND.

…the sides were shitty but I gained 4 pounds in a week and I leaned out at got dryer so I believe it was all lean mass. Be warned tho, the muscle you inject into gets SORE like when I did my legs I was strait up hobbling everywhere” forum user Cauthen96: He took a different approach by overloading with 1mg to start, followed by 100mcg bilaterally every day for 20 days straight (alongside other drugs such as CJC-1295 DAC and Tesamorelin), claiming lean muscle gains from 25lbs to 50lbs in ~2 months forum user Mike Arnold: Claims to have used one high-quality batch at 100-200 mcg per day, starting he gained 17 pounds in 21 days without any changes to his diet or anabolic steroid usage (although not exactly clear how much of it was muscle versus fat) forum user knucklehed: “I got stronger and I am still stronger then ever. My weight was up to 218-220 5 days post folli and I was full and tight.
But its hard to measure gains in lean mass… But I feel bigger and stronger…”

Animal Studies

At this stage, the majority of evidence does not involve directly injecting the Follistatin 344 peptide directly.

Instead, an adeno-associated virus (AAV) carrier is used:

“Follistatin was first isolated from the ovary and is known to suppress follicle-stimulating hormone. This raises concerns for potential adverse effects on the hypothalamic–pituitary–gonadal axis and possible reproductive capabilities.

In this review we demonstrate a strategy to bypass off-target effects using an alternatively spliced cDNA of follistatin (FS344) delivered by adeno-associated virus (AAV) to muscle.

The transgene product is a peptide of 315 amino acids that is secreted from the muscle and circulates in the serum, thus avoiding cell-surface binding sites. Using this approach our translational studies show increased muscle size and strength in species ranging from mice to monkeys”

This is what allows for a more selective approach in producing more follistatin without also having its undesired effects.

There have been numerous animal studies done — here are my favorites:

In this 2018 study, mice were injected with a nanoparticle mRNA delivery system that would produce follistatin — or a placebo — once every 72 hours:

“The therapy is based on nanoparticle-mediated delivery of follistatin messenger RNA (mRNA) to the liver after subcutaneous administration. The delivered mRNA directs hepatic cellular machinery to produce follistatin, a glycoprotein that increases lean mass through inhibition of negative regulators of muscle mass (myostatin and activin A).

… mRNA-loaded nanoparticles enter systemic circulation following subcutaneous injection, accumulate and internalize in the liver, where the mRNA is translated into follistatin… After eight weeks of repeated injections, the lean mass of mice in the treatment group was ~10% higher when compared to that of the controls”

But it doesn’t just stop at mice, because we also see Follistatin 334’s effects in trout:

“Transgenic rainbow trout (Oncorhynchus mykiss) overexpressing follistatin, one of the more efficacious antagonists of myostatin, were produced to investigate the effect of this protein on muscle development and growth. P1 transgenics overexpressing follistatin in muscle tissue exhibited increased epaxial and hypaxial muscling similar to that observed in double-muscled cattle and myostatin null mice.

The hypaxial muscling generated a phenotype reminiscent of well-developed rectus abdominus and intercostal muscles in humans and was dubbed “six pack”…  The increased muscling was due almost exclusively to hyperplasia as evidenced by a higher number of fibers per unit area and increases in the percentage of smaller fibers and the number of total fibers… It remains to be determined whether the double muscling in trout is due to inhibition of myostatin, other growth factors, or both.”

How about pigs? Turns out Follistatin 344 can do them too:

“Here, we describe transgenic Duroc pigs that exogenously express [Follistatin] specifically in muscle tissue. The transgenic pigs exhibited an increased proportion of skeletal muscle and a reduced proportion of body fat that were similar to those reported in myostatin-null cattle. The lean percentage of lean meat was significantly higher in the F1 generation of [transgenic] pigs (72.95 ± 1.0 %) than in [wild-type] pigs (69.18 ± 0.97 %) (N = 16, P < 0.05)…. 

…Moreover, no cardiac muscle hypertrophy or reproductive abnormality was observed. These findings indicate that muscle-specific Fst overexpression in pigs enhances skeletal muscle growth, at least partly due to myofiber hypertrophy”

Human Trials

This is where the story for myostatin inhibition may come to an end.

While clinical trials were initially successful in Phase I and Phase II, ultimately Follistatin 344 (with or without an AAV carrier) did not produce the desired results and neither did its competitors.

The fundamental reason comes down to how differently myostatin is expressed in mice vs humans:

“The differential growth of skeletal muscle in the pre- and post-natal environment is important to this story because proof of concept efficacy of myostatin inhibition in animal models of DMD [Duchenne muscular dystrophy] was initially proven through MSTN knockout (KO), which manipulates both pre- and post-natal hyperplastic and hypertrophic muscling.

This is in stark contrast to drug inhibitors of myostatin, which can only manipulate the post-natal hypertrophic growth of muscle. It might be that myostatin inhibition is much more influential on global muscle mass when applied from the earliest muscle growth during embryogenesis—this explains the phenomenal impact of MSTN [myostatin] mutations in mice, larger order animals (dogs, sheep, cows, horses) and humans”

But rest assured, nobody has 100% given up on targeting myostatin just yet.

It may just be the case that we have to critically look at other compounds Follistatin 344 interacts with and their respective role in the building and maintenance of skeletal muscle mass.

Follistatin 344 Dosage

The consensus about the best Follistatin 344 dose for muscle growth is the following:

100 mcg injected subcutaneously once a day for a 10-30 day cycle, followed by a 3-4 week break before resuming another cycle if needed.

I will say that due to the highly experimental nature of the Follistatin 344 peptide, there remains some uncertainty about what is most optimal for dosing:

  • Some people are unsure of timing (i.e. fasted in the morning, before/after training, nighttime, etc.)
  • Others insist Follistatin 344 has to be injected intramuscularly into the muscle you want to grow (in which case you need to split your injections bilaterally into the muscle)
  • It seems as if beyond 200 mcg a day, you don’t see an additional improvement in results

I’m afraid I don’t have much else to offer outside of this sparse intel for dosing Follistatin 344.

But as with any peptide, make sure you follow the proper protocols for peptide reconstitution and storage so you don’t end up injected something degraded into your body.

Follistatin 344 Side Effects

Follistatin 344’s side effects are almost nowhere to be seen in the medical literature save for a few human studies.

No surprise to me — very few people have been brave enough to even attempt procuring and using this peptide.

Some of the common side effects from Follistatin 344, as reported by anonymous bodybuilders, are as follows:

* Many testimonials are tainted by people who are running other compounds alongside Follistatin 344 (HGH, insulin, anabolic steroids, SARMS, testosterone, etc.), eating well above their maintenance caloric intake,

** A protein tag is “a useful and convenient tool for improving the solubility of recombinant proteins, streamlining protein purification, and allowing an easy way to track proteins during protein expression and purification” (Source, more info here and here).

At the same time, there is enough clinical data to suggest there are legitimate concerns associated with using Follistatin 344:

But even putting all of the above aside, Follistatin 344 has been a BANNED substance by the World Anti-Doping Association (WADA) since 2019:

“S4 Hormone and Metabolic Modulators… 4. Agents preventing activin receptor IIB activation including, but not limited, to: 

Myostatin inhibitors such as: Agents reducing or ablating myostatin expression; Myostatin-binding proteins (e.g. follistatin, myostatin propeptide); Myostatin-neutralizing antibodies  (e.g. domagrozumab, landogrozumab, stamulumab).”

Not to mention modern drug tests are exceedingly good at detecting black market Follistatin 344 and can easily differentiate between exogenous Follistatin 344 (i.e. injected into your body) and endogenous Follistatin 344 (i.e. naturally produced by your body).

And to really put the nail in the coffin, Follistatin 344 alone is an unsuitable drug candidate due to its poor half-life of 90 minutes and how easily it gets cleared by the liver.

Several studies (such as here and here) have and are continuing to pursue Follistatin 344 analogues that are more resistant to degradation, have a lower clearance rate and are more selective for myostatin inhibition.

In short: Follistatin 344 is FAR from a perfect therapeutic peptide, and I cannot comment any further as I have not used it in any capacity and ASSUREDLY never will (at least in its current form and fashion).

It will be up to any interested scientists and guinea-pig biohackers to determine Follistatin 344’s true safety and effectiveness.

Where to Buy Follistatin

I’m going to cut straight to the chase: I do not recommend buying the Follistatin 344 peptide for several reasons. 

First, at least half of the Follistatin 344 vials sold on the black market are garbage.

Follistatin 344 molecules stuck together, all the vials containing “tagged” Follistatin 344, presence of growth-hormone releasing peptides (GHRPs) in some vials, etc.

So there’s a good chance the product you’re receiving isn’t the real thing… IF your vial even contains any Follistatin 344 at all.

Second, the prices for a single cycle of Follistatin 344 are ludicrous.

One published study looking at black market prices for doping drugs found Follistatin 344 at £62-100 for every 5mcg (~76-122 in USD for 50% of a SINGLE dose)!

And we’re just talking about pure Follistatin 344, NOT the adeno-associated virus used to produce more Follistatin in the human body:

“Do realize how much real follistatin costs? Try over $4500 for 1mg… I’m not doubting you have something that is helping with your gains but I don’t believe any of these pep companies are selling real follistatin.

Here is a link to real follistatin from an actual biotech company (read: not a BBing ‘research chemical’ company)… as you can see, 1mg of Human Recombinant Folli is more than $4600.

The adeno-associated virus used to deliver follistatin runs about $500 on it’s own”

Combined with numerous complaints about product quality and unwanted side effects from vendors previously thought to be reputable, there’s really no point in wasting your money on Follistatin 344 right now.

If you REALLY want to dish some cash on a peptide for lean tissue gain, read my article on muscle-building peptides and go with either CJC-1295/Ipamorelin or 5-Amino 1MQ.

All three of those peptides should be sourced from no other place on the planet than Limitless Life Nootropics.

Use code JAY15 at the checkout cart for 15% off!

Conclusion: Stay Away From Follistatin 344 (For Now)

Follistatin 344 is a therapeutic muscle-building peptide I’ve been hounded about yet ignored for a long time, and not by accident.

I don’t deny it has great potential and its underlying mechanism is sound… but the lack of solid clinical evidence combined with many unanswered questions leaves me skeptical.

This compound deserves its heyday in the spotlight but it has to be earned, just like the ones I use in my peptide stack for fully optimized health.

I’ll leave you with three additional reading resources if you’re interested in learning more about Follistatin 344…

This website appears to be the closest thing to an official hub for Follistatin 344, complete with information about the peptide’s history and background. 

This Medium article I came across does a great job of summarizing the current state of myostatin inhibitors

And last but certainly not least, anybody brand new to the therapeutic peptides space needs to read my FREE “Top 10 Mistakes People Make When Starting Therapeutic Peptides” PDF!


You need to read this book thoroughly before using my most highly recommended peptides… let alone something highly experimental and unknown such as Follistatin 344.

Make sure you read the email sequence you get after opting in thoroughly as well, because hidden somewhere is a discount code for saving 50% on my premium Therapeutic Peptides Course.

As always…

Raise Your Vibration To Optimize Your Love Creation!

PS – Want to know about ALL the therapeutic peptides I’m taking an interest in, even if I never use them or mention them in public? If so, join The Fully Optimized Health Private Membership Group.

It’s your greatest opportunity to fully optimize your health and gain total access to me and my network of high-level men and women living their highest and best life.

Zoom with Jay

Schedule your call to talk one-on-one with Jay Campbell via Zoom.

Schedule Call