Black market Follistatin 344 is often fake, contaminated with GHRP-2, and contains traceable His-tags
Background
Follistatin is a myostatin-inhibiting protein sought for its muscle-building potential, leading to its inclusion in the WADA Prohibited List under S4 (Hormone and Metabolic Modulators). Despite having no approved pharmaceutical formulations, products labeled "follistatin 344" (FS344) and "follistatin 315" are widely available on the black market for performance enhancement. The authenticity, purity, and composition of these unregulated products are completely unknown, posing risks to users and creating challenges for anti-doping authorities who need reliable methods to detect their use and distinguish them from the body's natural follistatin.
Study Design
Researchers analyzed 17 black market products labeled as Follistatin 344. They developed and validated a detection method for FS344 in both serum and urine. The method involved an immunomagnetic purification step using immunoprecipitation (IP) with a polyclonal anti-follistatin antibody. This was followed by SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) and Western blotting for detection. Two different monoclonal antibodies were evaluated for the Western blot: an anti-His antibody and an anti-follistatin antibody. The study also assessed various commercially available follistatin standards.
Results
Of the 17 black market products tested, only 9 actually contained follistatin. Several of the fraudulent products contained other growth-promoting peptides, such as Mechano Growth Factor (MGF) and Growth Hormone Releasing Peptide-2 (GHRP-2). A surprising and critical finding was that 100% of the 9 legitimate FS344 products contained His-tagged follistatin, along with a high degree of its oligomers (polymers). The presence of these synthetic His-tags allows for unambiguous differentiation from endogenous, naturally occurring follistatin.
The newly developed detection method demonstrated high sensitivity, achieving a limit of detection (LOD) of approximately 0.1 ng/mL in a 10 mL urine sample and 5 ng/mL in a 100 μL serum sample.
Key Findings
- Only 9 out of 17 tested black market follistatin products actually contained the substance.
- Contaminants in fake products included other growth-promoting peptides like MGF and GHRP-2.
- All 9 genuine products contained His-tagged Follistatin 344, distinguishing them from endogenous follistatin.
- The detection method achieved a limit of detection of ~0.1 ng/mL in urine and 5 ng/mL in serum.
- A high degree of follistatin oligomers was present in the genuine black market samples.
Why It Matters
This research provides a crucial tool for anti-doping agencies to identify the use of black market follistatin. The discovery that all tested genuine products contain His-tags is a game-changer for testing, as it provides a clear, synthetic marker that separates illicit use from natural physiological levels. For users, this study is a stark warning: nearly half of tested follistatin products were fake, and some contained entirely different, unlabeled peptides like GHRP-2, creating unpredictable risks and effects. The high prevalence of oligomers also suggests potential issues with product quality and stability. This method makes it significantly easier to enforce the WADA ban on follistatin.
