Table of Contents
Definition of Puberty
The transition from childhood to the sexual and reproductive maturity that marks adulthood. Puberty occurs under the influence of hormonal shifts. The path of puberty tends to start and end about two years earlier for girls than for boys.
Puberty in most industrialized parts of the world begins between ages 10 to 15 and concludes between ages 17 to 19.
Puberty begins with hormonal changes the hypothalamus and the pituitary gland initiate that stimulate the gonads (ovaries in women and testicles in men) to begin producing gonadotropins (sex hormones)—estrogens and androgens. The pineal gland, which regulates the body’s circadian rhythms, also appears to play a role.
Researchers do not know what triggers these changes. Because external factors such as nutritional status and illness can influence the timing of puberty, researchers suspect body mass (height and weight) may somehow signal the endocrine system. Chromosomal disorders involving the sex chromosomes, such as Turner’s syndrome, which affects girls, and Klinefelter’s syndrome, which affects boys, alter or prevent natural puberty.
In both sexes, the first indication of puberty is the growth of hair under the arms and around the genitalia. At first the hair is light and fine; as puberty progresses the hair darkens and thickens. Hair on the legs also darkens and becomes more dense.
There is usually an accompanying growth spurt, which in boys particularly may amount to six inches or more of height within a year. Boys begin to broaden at the shoulders and girls at the hips during this surge of growth. The remaining changes that occur with puberty are gender specific.
Puberty in Girls
Breast buds, firm bumps that form beneath the nipples, mark the onset of estrogen-driven changes occurring in the girl’s body. In most girls breast budding occurs simultaneously with the development of pubic and axillary hair though one set of events may precede the other.
Over the course of one to three years the breasts continue to grow and take form and the girl’s body takes on a womanly appearance. Generally, about the time the pattern of body hair becomes adult-like the girl begins to menstruate, indicating her ovaries are mature and functional.
Puberty concludes in girls when the menstrual cycle is regular and predictable. External factors that can influence the start of menstruation (menarche) include obesity, which tends to cause earlier menarche, and intense physical activity such as athletic competition, which tends to cause later menarche. Both are within the range of normal.
Puberty in Boys
Enlargement of the scrotum and testicles marks the onset of testosterone-driven changes occurring in the boy’s body. The boy’s voice lowers in register and deepens. Growth continues at a rapid rate. Over the course of one to three years the penis thickens and elongates, and the testicles begin producing sperm.
Sexually stimulated erection and nocturnal emission (“wet dreams”) are common. Toward the conclusion of puberty hair on the arms may also become darker, longer, and more dense, and hair begins to grow on the chest.
Puberty concludes in boys when the genitalia reach adult proportions, which occurs at age 15 to 19.
Occasionally disturbances of hormonal function may result in early, or precocious, puberty, which doctors define as the onset of puberty before age 8 in girls and age 9 in boys. Treatment for precocious puberty depends on the underlying cause of the hormonal disturbance when the doctor can identify it; a common cause is pituitary adenoma (noncancerous tumor in the pituitary gland).
Often the cause remains unknown (idiopathic precocious puberty), in which case the doctor may administer gonadotropin-releasing hormone (gnrh) to regulate the pituitary gland’s release of luteinizing hormone (lh), the hormone that stimulates estrogen and testosterone. There are usually no adverse effects of idiopathic precocious puberty.
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