Follistatin 344
Follistatin isoform FST-344 (recombinant human follistatin, 344 amino acids)
Human data is very limited. Most evidence comes from case reports or observational studies.
A naturally occurring protein that blocks signals limiting muscle growth. A gene therapy version showed promise for Becker muscular dystrophy in a small clinical trial. The injectable form available through unregulated sources has no controlled human evidence and quality cannot be guaranteed.
This entry is a cited research summary, not an established treatment reference. Dosing language is included as source context, not as medical instruction.
Safety Summary
Safety data is extremely limited for injectable recombinant follistatin. No consistent side-effect profile for direct FS344 peptide use has been established. The most controlled data comes from AAV gene therapy trials: the Phase 1/2a BMD trial (6 patients) reported no adverse effects (PMC5240576; PMC4426808), and the sIBM trial (3 patients at low dose) reported no adverse events (PMC5240576). Minicircle's gene therapy program (500+ patients) reported the most common side effect as a slight LDL increase (~8 mg/dl) in roughly one-third of patients, which they describe as not clinically significant (minicircle.io). Community reports of injectable use include flu-like symptoms from a single online communities user, and weakened ligaments/tendons from bodybuilding community reports (SelfHacked). These effects may be attributable to product impurities rather than follistatin itself, given that only 9/17 tested products contained actual follistatin (PMID 31758732). Myostatin is expressed in cardiac tissue, and chronic inhibition raises theoretical cardiovascular concerns, but no long-term human data addresses this (peptidesunleashed.com). Black-market adulteration remains a separate and substantial safety concern (PMID 31758732).
Clinical check-in
If real-world use or exposure is being considered, review potential interactions, contraindications, and monitoring needs with a licensed clinician rather than relying on summary copy alone.
Sources: [1-10]