When some guys get much bigger from weight training and others don’t, it’s not because the big responders have more of these male hormones inside their muscles — both groups have about the same levels, so something else must be causing the difference.

Some people who lift weights and end up with more of a certain protein in their muscles tend to grow bigger muscles, but not everyone sees this link—some people with lots of the protein don’t grow much, and others with less do.

If you're a young, fit guy who already lifts weights, doing more weight training for 12 weeks won't change how many androgen receptors are in your muscles—but the number you started with can tell you how much bigger your muscles will get.

When young guys who don’t work out start lifting weights, their muscles grow more because of changes inside the muscle itself—like more hormone sensors and activation signals—rather than because of hormones floating in their blood.

If you're a young, fit guy who lifts weights, having more androgen receptors in your muscles might mean you gain more muscle size and strength after 12 weeks of training compared to others.

Even after a super hard workout, the body’s baseline testosterone level doesn’t stay high the next day — it goes back to normal quickly.