They prematurely signal bones to stop growing. When the steroids are used at a young age, it increases the sex hormone levels. These levels signal to the bones that growth is no longer needed.
This can lead to a shorter than average stature. Many take steroids to increase their muscles, but they consume it without regard to the effects the steroids can have to the other parts of the body. Steroids can cause acne, impacting their skin. It can also create a male user to grow unwanted breasts. Worst of all, steroids can lead to incurable cancer.