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between 9 and 14 years for girls and between 10 and 17 years for boys (Marshall & Tanner,
1986).[3]
Puberty begins when the pituitary gland begins to stimulate the production of the male sex
hormone testosterone in boys and the female sex hormonesestrogen and progesterone in girls.
The release of these sex hormones triggers the development of
the primary sex characteristics, the sex organs concerned with reproduction (Figure 6.9 "Sex
Characteristics"). These changes include the enlargement of the testicles and the penis in boys
and the development of the ovaries, uterus, and vagina in girls. In addition,
secondary sex characteristics (features that distinguish the two sexes from each other but are not
involved in reproduction) are also developing, such as an enlarged Adam’s apple, a deeper voice,
and pubic and underarm hair in boys and enlargement of the breasts, hips, and the appearance of
pubic and underarm hair in girls (Figure 6.9 "Sex Characteristics"). The enlargement of breasts is
usually the first sign of puberty in girls and, on average, occurs between ages 10 and 12
(Marshall & Tanner, 1986). [4] Boys typically begin to grow facial hair between ages 14 and 16,
and both boys and girls experience a rapid growth spurt during this stage. The growth spurt for
girls usually occurs earlier than that for boys, with some boys continuing to grow into their 20s.
Figure 6.9 Sex Characteristics