IGF1
IGF1 — the molecular target that 1 compounds in the wiki act on.
In one line: The powerful muscle-and-tissue growth signal that growth hormone works through.
IGF-1 is a growth factor — one of the body's strongest signals to build muscle and repair tissue. Much of growth hormone's effect actually happens through IGF-1, which the liver releases in response. Some athletes inject a long-acting version directly for its potent muscle-building effect.
The double edge is sharp: the very same "grow" signal that builds muscle can also feed tumours and drop blood sugar dangerously — which is why injected IGF-1 is high-risk and why growth-factor drugs carry cancer cautions.