FAQs

I have two boys who are 11 and 12 years old. Can you tell me about the physical changes that happen in boys at puberty?

Answer

The major growth spurt in males is controlled by both testosterone and the growth hormone, with virtually every muscle and bone in the body affected, including the genitals.

o Stage 1 pre-adolescence
Penis, testes and scrotum are of similar size and proportion as in early childhood.
o Stage 2 age 10-13 years
Scrotum and testes enlarge; one testicle usually hangs lower than the other; the scrotum becomes baggier, slightly furrowed and reddened and sperm development (spermatogenesis) begins within the testes. At this time a boy may begin to notice 'wet dreams' or nocturnal emission. This is the involuntary ejaculation of semen experienced by boys and men during sleep.
o Stage 3 age 11-14 years
Testicles and scrotum grow larger; penis starts to lengthen, and becomes broader; sparse pubic hair develops; facial hair appears on upper lip and cheeks; thicker body hair starts to appear on limbs and trunk.
o Stages 4 age 13-17 years (major growth spurt ;)
Further enlargement of the testes and scrotum; scrotum darkens and becomes more furrowed; penis continues enlarging; pubic and body hair become even thicker and more widespread, with hair growing around the base of the penis.
o Stage 5 age 17-19 (Adult stage)
Genitals fully matured; pubic hair extends up the abdominal midline; facial hair extends to lower lip and chin.

The over-riding message from all this is that everyone develops at their own pace. Those who start earlier usually stop earlier as well. The size of the average adult male penis, particularly the erect penis, actually doesn't vary all that much from man to man.

http://www.fpnsw.org.au/sex-matters/faq/penis_20020703.html