Puberty in Boys
Puberty is the stage during which people reach full reproductive ability and develop the adult features of their sex. In boys, puberty usually occurs between the ages of 10 and 14 years. However, it is not unusual for puberty to begin as early as age 9 or to continue until age 16.
The hypothalamus and pituitary gland, which are in the brain, initiate puberty. The hypothalamus secretes luteinizing hormone-releasing hormone, which stimulates the pituitary to secrete luteinizing hormone and follicle-stimulating hormone. Luteinizing hormone causes the testes to produce testosterone. Follicle-stimulating hormone (plus testosterone) causes the testes to produce sperm. Testosterone is responsible for the development of secondary sex characteristics, features that stimulate male development (including characteristics that are not part of the reproductive system, such as facial hair growth and voice change).
Sexual development occurs in a set sequence:
Enlargement of the scrotum, and testes
Lengthening of the penis (around age 11½ to 13 years)
Enlargement of seminal vesicles and prostate gland
Growth of pubic hair
Growth of hair on face and in the underarms (about 2 years after pubic hair growth starts)
Ejaculation becomes possible (usually in mid-adolescence, around age 12½ to 14 years)
Fertility is not attained until later in adolescence. Breast enlargement (gynecomastia) on one side or both may occur among young adolescent boys and usually disappears within a year.