Follistatin inhibits myostatin, which limits muscle growth — the mechanism is real and fascinating. The famous "super-muscled" whippet dogs and cattle breeds are genuine myostatin-deficiency cases. But the human evidence for injectable follistatin is essentially a single gene therapy study in boys with muscular dystrophy, not healthy athletes. Follistatin has a complex regulatory role beyond muscle (it affects reproductive hormones, bone, and adipose tissue). Injecting it without understanding those systemic effects isn't biohacking — it's experimental gene pharmacology without a protocol.