Hormonal

Testosterone administration in eugonadal men produces a dose-dependent increase in fat-free mass, muscle volume, strength, and power, following a single linear dose-response relationship without evidence of receptor saturation at supraphysiological levels.

If you are a healthy young man with normal testosterone, adding exogenous testosterone will increase your muscle mass and strength in direct proportion to the dose, even at levels far above what your body naturally produces. You do not need to train harder or eat more protein than normal to see these gains, as the hormonal driver is the primary factor. However, higher doses bring higher risks for side effects like acne and negative lipid changes.