if you take steroids and masturbate a lot, would you dick get bigger since you are "working out a muscle"?
<span style="color: red">~~Don't make someone a priority when you're only an option~~</span>
The penis is NOT a muscle; it is erectile tissue. There is a small amount of muscle tissue at the very base, but it does little to nothing.
Meaning: the tissue reacts to blood flow alone
Steroids themselves will actually lead to a decrease of various hormones including testosterone (meaning you'll have a lower sex drive, VERY small testicles etc) and when you get off the 'roids, you could have a life-long imbalance of those hormones.
The penis is mostly spongy tissue. It can only get bigger by absorbing blood.