Puberty

The process of physical growth and sexual maturation that signals the end of childhood and the advent of adolescence. (Also, the period during which this process takes place.)

The word puberty is derived from the Latin pubertas, which means adulthood. Puberty is initiated by hormonal changes triggered by a part of the brain called the hypothalamus, which stimulates the pituitary gland, which in turn activates other glands as well. These changes begin about a year before any of their results are visible. Both the male reproductive hormone testosterone and female hormone estrogen are present in children of both sexes. However, their balance changes at puberty, with girls producing relatively more estrogen and boys producing more testosterone.

Most experts suggest that parents begin short and casual discussions about puberty with their children by the age of seven or eight. Offering the child reading materials about puberty can impart information to the young person without the awkwardness that may characterize the parent-child conversations. Parents can then offer their children opportunities to ask questions or to discuss any aspects of puberty and sexuality that may arise from their reading.

The first obvious sign of puberty is a growth spurt that typically occurs in girls between the ages of 10 and 14 and in boys between 12 and 16. Between these ages both sexes grow about nine inches. The average girl gains about 38 pounds, and the average boy gains about42. One reason for the awkwardness of adolescence is the fact that this growth spurt proceeds at different rates in different parts of the body. Hands and feet grow faster than arms and legs, which, in turn, lengthen before the torso does, all of which create the impression of gawkiness common to many teenagers. In addition, there can be temporary unevenness of growth on the two sides of the body, and even facial development is disproportionate, as the nose, lips, and ears grow before the head attains its full adult size. The growth spurt at puberty is not solely an external one. Various internal organs increase significantly in size, in some cases with observable consequences. Increases in heart and lung size and in the total volume of blood give adolescents increased strength and endurance for athletics and for recreational activities such as dancing. (During puberty, the heart doubles in size.) Teenagers' ravenous appetites are related to the increased capacity of the digestive system, and the decrease in respiratory problems (including asthma) is associated with the fact that the lymphoid system, which includes the tonsils and adenoids, actually shrinks in adolescence. Yet another change, the increase in secretions from the sebaceous glands, triggered by the growth hormone androgen, is responsible for acne, which affects about 75% of teenagers. The excess oil from these glands clogs pores, and they become inflamed, causing the reddening and swelling of acne.

Following the beginning of the growth spurt, the sexual organs begin to mature and secondary sex characteristics appear. In girls, the uterus and vagina become larger, and the lining of the vagina thickens. The first visible sign of sexual maturation is often the appearance of a small amount of colorless pubic hair shortly after the growth spurt begins. Over the next three years, the pubic hair becomes thicker, darker, coarser, and curlier and spreads to cover a larger area. Hair also develops under the arms, on the arms and legs (sufficiently so that most girls start shaving), and, to a slight degree, on the face. Around the age of 10 or 11, "breast buds," the first sign of breast development, appear. Full breast development takes about three or four years and is generally not complete until puberty is almost over. The single most dramatic sign of sexual maturation in girls is menarche, the onset of menstruation, which usually occurs after a girl's growth rate has peaked. In virtually all cases it occurs between the ages of 10 and 16, with the average age in the United States being 12.8 years. The first menstrual periods are usually anovulatory, meaning that they happen without ovulation. Periods remain irregular for a while, and for at

HORMONE SURGE TRIGGERS PUBERTY

A point in child development known as adrenarche—the beginning of adrenal androgen activity—may represent the beginning of the process of puberty. Two University of Chicago researchers, Dr. Martha K. McClintock and Dr. Gilbert Herdt, believe that puberty is triggered by dihydroepiandrosterone (DHEA), a hormone produced by the adrenal glands. According to data the two gathered from three separate studies, DHEA levels begin to increase at around the age of six and reach a critical level around age ten. The researchers characterize these hormonal changes as triggering a number of cognitive, emotional, and social changes in around fourth or fifth grade. Students in these grades begin to engage in boy-girl teasing, exhibit a significant increase in abstract reasoning skills, and experience vulnerability to embarrassment. The three studies also gathered data on subjects' (who were mostly in their mid 30s) first recollected feelings of sexual attraction. The mean age reported by the subjects was around 10 or 11. This finding has led the researchers to postulate that sexual development moves along a continuum, beginning with attraction, progressing to desire, and leading to the willingness and readiness to act on the desire. McClintock, quoted in the New York Times, noted: "Our culture regards middle childhood as a time of hormonal quiescence. Freud called it 'latency.' But actually a great deal of activity is going on."

least a year after menarche young women's fertility levels are very low, and they are prone to spontaneous abortions if they do conceive.

In boys, as in girls, the first outward sign of sexual maturation is often light-colored pubic hair around the time the growth spurt begins. The testes and scrotum begin to grow, and the scrotum darkens, thickens, and becomes pendulous. About a year after the testes begin to increase in size, the penis lengthens and widens, taking several years to reach its full size. Sperm production increases, and ejaculations—the male counterpart to menarche in girls—begin, occurring through nocturnal emission, masturbation, or sexual intercourse. (It takes from one to three years until ejaculations contain enough sperm for a boy to be really fertile.) Boys' pubic hair, like that of girls, gradually becomes thicker and curlier and covers a wider area, and facial hair appears, first in the mustache area above the upper lip and later at the sides of the face and on the chin. As a boy's larynx grows and the vocal cords lengthen, his voice drops (roughly an octave in pitch) and changes in quality. Although girls' voices also become lower, the change is more dramatic (and less controlled) in boys, whose voices occasionally break, producing an embarrassing high-pitched squeak.

The sequence and age range of the developmental changes associated with puberty can vary widely. Although most children begin puberty between the ages of 10 and 12, it can start at any age from 8 to 16. The most obvious determining factor is gender; on average, puberty arrives earlier for girls than boys. Heredity also appears to play an important role. Compared to an overall age range of nine to 18 for menarche, the age difference for sisters averages only 13 months and for identical twins, less than three months. Body weight is a factor as well: puberty often begins earlier in heavier children of both sexes and later in thinner ones. The onset of menstruation, in particular, appears to be related to amounts of body fat. Girls with little body fat, especially athletes, often start menstruating at a later-than-average age. Over the past 100 years, puberty has tended to begin increasingly early in both sexes (a phenomenon called the secular trend). In 1997, the results of a study led by Dr. Marcia E. Herman-Giddens of University of North Carolina at Chapel Hill School of Public Health provided evidence that the average age of menarche was declining. Instead of occurring between the ages of 12 and 14, as is typical in the late 1990s, girls' first menstrual periods commonly appeared between the ages of 15 and 17 in the 19th century. Puberty in boys usually didn't begin until the ages of 15 or 16 (in the late 18th and early 19th centuries, boy sopranos in their mid-to-late teens still sang in church choirs). Explanations for this pattern have ranged from evolution to better health, especially as a consequence of improved nutrition.

An important aspect of puberty is the development of body image. Teenagers are often critical of their bodies during this period, either because they feel they are maturing too early or too late, or because they fail to match the stereotyped ideals of attractiveness for their sex (i.e., tall and muscular for men, fashionably thin for women). Girls who mature early have a hard time initially because they feel self-conscious and isolated, but they adjust well and even gain in status once their peers begin to catch up. Some research even suggests that girls who mature early may ultimately be better off than those who mature late because the turmoil of their early teenage years helps them develop coping skills that stand them in good stead later on. For boys, the relative positions of early and late maturers is reversed. Those who are already tall and athletic in junior high school feel better about themselves than those who remain short and skinny. Researchers have linked late physical maturation in boys to the development

of both positive personalitytraits (humor, perceptiveness, flexibility, creativity, and leadership skills) and negative ones (restlessness and lack of poise). In most cases, adolescents gradually become more accepting of their bodies in the years following junior high school.