Follistatin-344
Follistatin-344 is a form of the natural protein follistatin, which binds and inhibits myostatin and related TGF-beta family ligands that limit muscle growth. It is marketed to bodybuilders for rapid muscle gain based on dramatic myostatin-knockout animal phenotypes. There are no controlled human trials of the injectable research peptide, and it is a large protein poorly suited to the crude subcutaneous dosing used.
01 Overview
Follistatin is an endogenous glycoprotein that sequesters myostatin (GDF-8) and activins, releasing the brake on muscle growth. Animal models with follistatin overexpression or myostatin loss show striking muscle hypertrophy, which drives intense interest in follistatin as a muscle-building agent. Follistatin-344 refers to a specific isoform sold as a research peptide.
02 Mechanism
Binds and neutralises myostatin (GDF-8) and activins, removing their inhibition of muscle satellite cell activity and protein synthesis, thereby permitting hypertrophy.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Anecdotal | 100–300 mcg/day | SubQ | Forum protocols run in short cycles. No validated dosing; systemic bioavailability of injected protein is questionable. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Muscle hypertrophy via myostatin inhibitionMyostatin blockade produces marked hypertrophy in animals; human effect from injected peptide unproven. | Large in animal models; unquantified in humans | Preclinical | |
| Claimed rapid muscle gainBodybuilding claims unsupported by controlled human data. | Unquantified | Anecdotal |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Injection-site reactionsLocal irritation at the injection site. | Mild | Common | Anecdotal | |
| Off-target TGF-beta effectsBecause follistatin also binds activins, systemic use could disturb reproductive and other TGF-beta-regulated axes; unstudied in this context. | Moderate | Uncharacterised | Unconfirmed |