Satellite Cells

Androgen Receptor

The receptor every anabolic-androgenic steroid is designed to hit. Binding moves it into the nucleus where it switches on genes for muscle protein synthesis, and in other tissues for hair loss, prostate growth and oil production.

Myonuclei

The nuclei inside a muscle fibre, each running a patch of it. Androgens add them, and animal work shows the added ones persist for a long time after the drug is gone. This is the cell-level reason a past cycle is never entirely undone.

Myostatin Signalling

The body's own brake on muscle growth. Lowering it removes a ceiling rather than adding a push, which is a different kind of effect from raising protein synthesis.