Puberty in Boys

ByIrvin H. Hirsch, MD, Sidney Kimmel Medical College of Thomas Jefferson University
Reviewed/Revised Feb 2023

    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.

    • At puberty, the testes increase testosterone production.

    • Testosterone causes reproductive organs to mature, muscle and bone to grow, facial and pubic hair to appear, and the voice to deepen.

    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 of 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.

    Milestones in Sexual Development

    During puberty, sexual development occurs in a set sequence. However, when the changes begin and how quickly they occur vary from person to person. For girls, puberty begins at age 8 1/2 to 10 years and lasts about 4 years. The chart shows a typical sequence and normal range of development for the milestones of sexual development.

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