Follistatin 344 Guía & Tabla de Dosis

What is Follistatin 344?

Follistatin 344 (often written FS-344) is a specific version — scientists call it an isoform — of a naturally occurring protein called follistatin. Your body already makes follistatin on its own. The "344" refers to how many amino acid building blocks make up this particular form of the protein.

In research settings, FS-344 is studied mainly because of its ability to block a molecule called myostatin — a natural brake your body puts on muscle growth. Researchers are curious: what happens to muscle tissue when that brake is loosened?

It's worth knowing upfront that no approved pharmaceutical version of follistatin 344 exists anywhere in the world right now.^[5] Any FS-344 you come across is an unapproved, research-grade compound. The World Anti-Doping Agency (WADA) lists follistatin as a prohibited substance under section S4 of its banned list.^[5] This page is for educational and research reference only — not medical advice.

How Follistatin 344 Works

Think of muscle growth like a car with both a gas pedal and a brake. Growth signals are the gas. Myostatin is the brake — it tells your muscles "that's enough, stop growing." Follistatin 344 works by binding tightly to myostatin and essentially holding the brake pedal up, allowing muscle-building signals to keep working longer and harder.

More precisely, FS-344 is what scientists call a binding protein. It latches onto myostatin (and a few related proteins in the same family) and stops them from activating their usual signaling pathway. That pathway runs through proteins called Smad2 — and research in transgenic pigs found that muscle-specific follistatin expression significantly reduced Smad2 activity, while also boosting another growth-promoting signal called AktS473.^[4] The result, at least in animal models, is bigger muscle fibers — a process called myofiber hypertrophy.^[4]

What the Research Shows

Most of the solid data on FS-344 comes from animal studies, with some human case reports adding important safety context.

Animal studies: muscle and body composition

A 2017 study created transgenic pigs that expressed human follistatin-344 specifically in their muscle tissue. The results were striking. These pigs had meaningfully more skeletal muscle and less body fat than normal pigs. Their lean meat percentage averaged about 73%, compared to roughly 69% in regular pigs — a statistically significant difference. Researchers also saw larger individual muscle fibers in a key back muscle. Importantly, the scientists found no heart muscle enlargement or reproductive problems in these animals.^[4]

What's actually in black-market products?

Anti-doping researchers in Europe bought 17 black-market products labeled "follistatin 344" and tested every one. Only 9 of the 17 actually contained follistatin at all. The others contained different peptides — including muscle-growth compounds like MGF and GHRP-2 — or nothing useful. Every product that did contain follistatin had a laboratory tag called a His-tag still attached (a manufacturing artifact not meant for use in living systems), and most contained large clumps of the protein called oligomers.^[5] A subsequent correction and update to that work was published in 2020.^[1] The takeaway: product quality and authenticity in unregulated markets is deeply unreliable.

Human safety signals

A retrospective case series from a hospital ophthalmology department reported 11 male bodybuilders who developed a serious eye condition called central serous chorioretinopathy (CSCR) after injecting high-dose follistatin-344. CSCR causes fluid to build up under the retina, leading to blurred or distorted vision. In the 8 patients who had injected only once, the fluid resolved on its own over about 2 months. In 3 patients who had injected multiple times, the condition recurred.^[3] This is a meaningful safety signal that researchers and clinicians take seriously.

A 2026 review in Sports Medicine summarized the state of the evidence for unapproved peptides including FS-344, noting that while some compounds show favorable results in animal models, rigorous human safety data remain scarce and the potential for serious harm is real.^[2]

What Follistatin 344 Is Being Studied For

• Muscle mass and myostatin inhibition — the core research question, based on animal model evidence^[4]
• Body composition changes — the pig study showed increased lean mass alongside reduced fat^[4]
• Athletic performance and doping detection — anti-doping labs have developed urine and serum tests to detect it^[5]
• Musculoskeletal injury and recovery — mentioned as an area of interest in sports medicine research^[2]

How Follistatin 344 Is Dosed in Research

Because FS-344 has no approved clinical use, there are no standardized dosing protocols validated in humans. The dosage chart on this page summarizes the dose ranges that appear in preclinical literature and researcher reports — use it as a reference point alongside the calculator to explore how volumes and concentrations relate to one another. Always note that the human safety profile of this compound is not well established, and the black-market case series involved a 1 mg single-dose injection that was associated with serious eye side effects in multiple individuals.^[3]

Mixing and Storing Follistatin 344

Follistatin 344, like most research peptides, comes as a freeze-dried (lyophilized) white powder in a sealed vial. To use it in a lab setting, researchers reconstitute it — that means dissolving the powder — typically using bacteriostatic water. Bacteriostatic water contains a small amount of benzyl alcohol that slows bacterial growth and extends the usable life of the reconstituted solution. Add the water slowly down the side of the vial; do not shake the vial, as this can damage the protein structure. Gently swirl or roll instead. Once mixed, the solution should be stored in a refrigerator (around 2–8 °C / 36–46 °F) and used within a few weeks. Unmixed powder can typically be stored longer at freezer temperatures. Always check the specific storage instructions from your supplier and discard any solution that appears cloudy or discolored.

Sources

1. Detection of black market follistatin 344. — Drug testing and analysis, 2020. PMID 33460286.
2. Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance. — Sports medicine (Auckland, N.Z.), 2026. PMID 41966639.
3. Central serous chorioretinopathy associated with high-dose follistatin-344: a retrospective case series. — International ophthalmology, 2020. PMID 32671599.
4. The transgenic expression of human follistatin-344 increases skeletal muscle mass in pigs. — Transgenic research, 2017. PMID 27787698.
5. Detection of black market follistatin 344. — Drug testing and analysis, 2019. PMID 31758732.