What it is
Peptides acting on it
Evidence
[educational]U-shaped IGF-1↔mortality in humans (too-low and too-high both raise mortality; animal models: lower IGF-1 → longer life). Each +38 ng/mL IGF-1 ≈ +8–18% risk for most cancers (GH/IGF-1 feed existing cancer, don’t cause it). — GH selection guide