Puberty is the period of physiological and anatomical development when the organs of sexual reproduction mature and become functional. This is not to be confused with adolescence, which is a socially defined period of psychological development that is sociocultural. Puberty may or may not coincide with adolescence and in some cultures adolescence does not exist. In females, the onset of menstruation and the development of the breasts mark this maturation. In males, the biological markers of puberty are the enlargement of the external genitalia and the production of semen. In both sexes, the development of these primary sexual characteristics is accompanied by the onset of a variety of secondary sexual characteristics. In males, these include the appearance of facial and other body hair, including in the pubic area and in the armpits, as well as the deepening of the voice tone. In females, hair develops in the pubic area and in the armpits, and the hips begin to broaden. For both sexes this is also a period of rapid development of the sweat glands. Generally, these changes prepare the body for sexual reproduction, but they also have important social and emotional aspects.

Among boys, puberty tends to begin at about age 13, but may not start until 16 years of age. Puberty tends to begin earlier in females, often two years earlier than boys. However, the commencement of puberty varies among girls no less than among boys, and may not begin until age 14 or 15. Heredity can influence the onset of puberty, as can psychological and physical health. Some studies have shown that earlier-maturing individuals achieve better social adjustment to puberty than do later-maturing individuals. This may be due to anxiety about being different from one's peers and accompanying social pressure for conformity common during the adolescent years. Conversely, some youths undergo a peculiarly early pubescent transition, a condition called pubertus praecox. The functioning of the anterior pituitary, adrenals, or the gonads causes this condition.

The beginning of puberty is controlled by the release of growth hormone by the pituitary gland. This biochemical substance produces rapid growth, which is characteristic of puberty. Girls most commonly begin a rapid growth period between the ages of 12-14 years, but some start this growth spurt as early as age nine. By the time they are 14, most girls have reached their adult height. Menstruation generally begins about three-fourths of the way through this rapid growth period. Breast changes and the growth of body hair precede the beginning of menstruation by about one year. The pattern for boys is somewhat different. The period of rapid adolescent growth for boys begins after age 12 and continues for about four years. The onset of the various features of puberty for boys occurs throughout this period. Boys commonly do not reach their adult height until several years after girls and may continue to grow and to develop secondary sex characteristics, such as chest hair, well into the late teen years. Other hormones also shape pubescence. In boys, androgen and in girls, estrogen sparks the development of secondary sex characteristics.

Puberty is a time of physical, emotional, and social exploration and self-discovery. Associated with the physical changes that characterize puberty is a growth in sexual interest. For most youths, this involves increased attentiveness to the opposite sex or heterosexual attraction; for others it involves an enhanced same-sex interest or homosexual attraction. Because of social disapproval, young people who find themselves sexually attracted to members of their own sex may undergo considerable emotional distress, isolation, and sexual guilt. However, the onset of bodily changes (at different times and at different rates among different youths), the beginnings of sexual interest and incipient romantic attractions, and the lack of a clear social role can contribute to uncertainty and confusion among both heterosexual and homosexual youths. Feelings of sexual attraction are part of the search for self-understanding and part of the normal developmental process called puberty.

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