Typical Age Range
This stage starts when the adolescent growth spurt slows down to childhood rates or less and ends when growth in height stops. On average it starts around age 15 but can start as early as 12 or as late as 18. It typically lasts about two years.
Characteristics and Changes During Stage 4:
Growth begins to slow, though an additional inch to three inches will be gained. It is the slowing down of the growth rate that is the primary marker for the start of stage 4.
The scrotum distinctly hangs and takes on a darker color. The testes are between 1 1/2 to 1 3/4 inches (4.1 to 4.5 cm) long measured along the long axis or measured in volume they are 12 to 20 ml.
The penis continues to grow, but mostly in width. The glans at the end of the penis widens and develops a distinct corona. If ejaculation of semen hasn’t happened earlier, it will begin in this stage.
Pubic hair is pigmented and curly, spreading across the groin. A strip of hair forms from the groin up to the navel. Hair under the arms becomes denser.
Facial hair develops on upper lip, chin, and near ears. Continues to spread across the face as this stage continues.
Voice continues to crack at times and deepens.
Acne breaks out on face and body.
If breasts stand out, they begin to disappear. Nipples stick out and become both harder and more sensitive to touch.
Muscles begin to develop.
Shoulders begin to widen to give a typical male physique. The trunk region grows, but it is at a slower rate than the growth of the legs in stage 3.
Still tends toward extremes in mood, though this settles down a bit.