What are puberty and adolescence?

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Puberty is the onset of the natural biochemical (hormonal) and physical changes that occur in children as they are transformed into sexually mature individuals; adolescence is the period of years during which these transformations take place.
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Causes and Symptoms

The development period known as adolescence encompasses a host of biochemical, physical, and psychological changes in an individual that result in maturation as an adult capable of sexual reproduction. Collectively, the biochemical changes that lead to sexual maturity are called puberty. The process occurs over several years, and its time of onset is difficult to detect because the initial physical changes are quite subtle. For boys and girls in the United States and Western Europe during the last half of the twentieth century, the average age at which the onset of puberty occurred was between eight and thirteen years in girls, and nine and fourteen years in boys. Medical researchers are noting an earlier onset of puberty for many children around the world, but the reasons for this shift are not yet well understood.

One of the most dramatic physical changes that occurs in puberty is a tremendous growth spurt. The rate of height increase per year doubles as compared with height gain prior to puberty. On the average, girls gain approximately 3 inches of height during this period, and boys grow by about 8 inches. The bulk of this growth is accounted for by an elongation of the thigh bones, followed by growth in the trunk. During this time, the thighs become wider, and shoulder width also increases. Both sexes accumulate fat during early puberty. Boys frequently appear rather chubby early in adolescence, but they generally lose this excess fat during their growth spurt. Most of this accumulated fat in girls is redistributed on their bodies and results in the typically curved silhouette. The average girl gains approximately 25 pounds during the adolescent period, while boys gain about 40 pounds, most of which is in the form of muscle.

Additional physical changes that occur during adolescence include changes in the facial bones, especially an elongation of the jawbone. Muscle size and strength increase during puberty, with a boy’s development in this area extending years past the end of muscle strength increase in the typical girl. Prior to puberty, muscular strength is equivalent in both sexes, but the increase stops at the time of the first menstrual period in girls. Each of the major organs of the body, including the digestive tract, liver, kidneys, and heart, increases in size for both sexes during puberty. The size and activity of various glands adjust to reflect their increasing or decreasing role in the maturing individual.

Both girls and boys experience a characteristic increase in the distribution of hair on their bodies. Axillary (armpit) hair and pubic hair increase in density and coarseness, finally achieving the characteristic adult pattern. Boys also develop facial hair, beginning with a fine fuzz on the upper lip and eventually progressing into a full beard. Sweat glands increase in size as well. Boys undergo an increase in the size of the larynx (voice box), and this change leads to the normal, although psychologically painful, “cracking” of the adolescent male’s voice.

Major alterations in the reproductive systems of boys and girls occur during puberty. In girls, the vagina enlarges and undergoes changes in chemical composition and cellular structure, and it begins producing typical adult secretions. Menarche, the first menstrual period, takes place even though ovulation (the maturation and release of an egg by the ovaries) may not occur for many months. The ovaries increase in size, and chemical changes prepare them to ovulate on a monthly basis. Breasts evolve from the preadolescent form to that of adult women. Boys undergo enlargement of the testicles, which are experiencing biochemical changes that prepare them for the continuous process of sperm production, as well as enlargement of the penis.

Because of the complexity of the many physical changes that occur during puberty, as well as the wide variation in the normal age of onset of this period, physicians have adopted a “sex maturity rating” scale to aid in their assessment of normal adolescent development. For both sexes, a rating of 1 (least mature) to 5 (most mature) is used to rank information collected by the visual observation of secondary sexual characteristics. For girls, breast and pubic hair development are the physical traits assessed. Boys are ranked based on the appearance of their genitals (penis and testicles) and the amount and distribution of their pubic hair.

All these physical changes are the direct result of global biochemical changes occurring in the adolescent’s body. Just prior to puberty, a hormone called luteinizing hormone-releasing factor (LHRF) is produced by a portion of the brain called the hypothalamus. The LHRF travels to another structure in the brain, the pituitary gland. Upon receiving this hormonal signal, the pituitary gland produces two additional hormones called gonadotropins. The gonadotropins stimulate the development and enlargement of the ovaries in girls and the testicles in boys. As a result of the stimulation of the gonadotropins, the gonads produce sex hormones; the ovaries produce estrogen, and the testes produce testosterone. Females also produce a small amount of testosterone in the adrenal glands, which are located above the kidneys. These sex hormones enter the bloodstream and signal the start of the physical changes associated with puberty.

Examples of the effects of these hormones include the development of axillary hair in both boys and girls, which is initiated and maintained by testosterone. Breast development in girls is triggered by the estrogen produced by the ovaries. Maturation of the larynx in boys is accomplished by the action of testosterone. The other physical changes noted above are the result of sex hormones working alone or in concert with each other and of hormonal action on the genetic information of the individual.

The psychological changes that take place during puberty, although normal, may be dramatic. Thinking and cognitive skills mature during this period, accompanied by a tendency to analyze the rules and values of families, friends, and society. Frequently, this is a period of rebellion against parents and other authority figures. The confusion frequently associated with the rapid changes in adolescents’ bodies and minds and their changing perceptions of their role in the world, coupled with the beginnings of adult responsibility, can lead to problems with self-esteem, anxiety, and depression. Critical and unreasonable self-assessment of appearance and abilities may lead to psychological illness. Socialization and self-identity come into prominence in the adolescent’s life and can result in additional confusion, feelings of rejection, and experimentation with alcohol and drugs.

Sexual feelings are awakened in the adolescent and can be particularly challenging to understand and channel in an appropriate and responsible manner. Discovery of a sexual orientation contrary to heterosexual interests can create severe psychological problems for the adolescent because of fear of rejection by family and society. The possibilities of pregnancy or fatherhood or the contraction of a sexually transmitted disease may add gravity to early sexual explorations. Many groups argue that adolescents should have access to accurate and nonjudgmental information on contraception and disease prevention.

Complications and Disorders

A number of medical disorders can result from abnormalities in the biochemical processes that mediate puberty. Other, less serious varieties of physical afflictions are natural and temporary side effects of the normal changes that accompany adolescence. Psychological disturbances may be associated with the extensive upheaval in the physical, mental, and social aspects of an adolescent’s life, and in most cases they do not reach severe proportions. In some instances, however, professional intervention is indicated.

If the onset of puberty is not evident by age thirteen in girls or age fourteen in boys, or if puberty is initiated but little progression is observed for six to twelve months, detailed medical evaluation of the situation is recommended. Oral histories and a complete physical examination are conducted, and the individual’s sex maturity rating is determined. The level of the gonadotropic hormones will first be assessed in order to determine if the delay of puberty is caused by a lack of the gonad-stimulating hormones produced by the brain or if the sex hormone production by the gonads is deficient.

A permanent deficiency in the amount of gonadotropic hormones produced by the pituitary gland prevents the sex organs from maturing and producing the sex hormones estrogen (in girls) and testosterone (in boys). This syndrome is referred to as hypogonadotropic hypogonadism and can be caused by a variety of central nervous system abnormalities. Congenital defects (abnormalities present at birth) in the pituitary gland can inhibit the production of gonadotropins. Likewise, tumors at certain positions in the brain, including the pituitary gland, may block hormone production. Deficiency in another hormone, human growth hormone, results in short stature and delayed puberty. Other conditions, such as genetic abnormalities, chronic disease, pathologies of the thyroid gland or its functions, malnutrition, and excessive exercise, can also be the root cause of delayed puberty.

Delayed puberty can also be caused by failure of the ovaries or testes to mature despite normal levels of gonadotropins produced by the brain. In the vast majority of cases, the root cause of this syndrome, hypogonadotropic hypogonadism, is linked to defects in the normal chromosomal complement of the individual; that is, it is a genetic defect. Usually, it is caused by the presence of abnormal sex chromosomes and is diagnosed by examination of the chromosomes by a procedure called karyotyping.

A third category of delayed puberty is termed “constitutional delay in puberty.” At the latest extreme of what is classified as the “average” age of onset of puberty, the individual’s stature may be short, menarche may be delayed in girls, and the sex maturity ranking for both sexes would be low. In reality, these individuals are merely slightly beyond the age of onset considered “normal” and will, without medical intervention, proceed through normal puberty and develop into fully mature adults of normal height. Patience and close observation of changes are the best course of action in cases of constitutional delay in puberty.

True cases of precocious puberty—that is, puberty with an extremely early onset because of physical or biochemical abnormalities—are extremely rare, occurring in about one in every ten thousand children. In these cases, there is usually a defect in one or more of the glands producing the hormones that initiate puberty. Skilled medical diagnosis is indicated in these cases. When puberty begins much earlier than expected, the physician will check for a number of potentially serious problems such as adrenal gland disorders, reproductive system cysts, nervous system disorders, and thyroid abnormalities. Early pubertal onset is considered to be prior to eight and one-half years in girls or nine and one-half years in boys.

Acne, or pimples and blackheads on the skin of the face and upper back, commonly appears during adolescence. This skin disorder is a by-product of the hormones produced at puberty, which also stimulate the production of oil in the glands of the face and back. Acne may be treated with over-the-counter remedies and frequent washing of the skin, and it usually disappears as the individual approaches adulthood. In some severe cases, however, in which infection and scarring are distinct possibilities, medical intervention is recommended.

Preoccupation with personal appearance, difficulties with self-esteem, and a host of other psychological factors connected with the upheavals experienced during adolescence can lead to eating disorders. Anorexia nervosa is a syndrome characterized by extremely low food intake, preoccupation with losing weight, maintaining a weight that is more than 15 percent below a normal level for age and height, disturbed perception of personal weight (seeing oneself as obese when one is pathologically thin), and (in girls) skipping three or more sequential menstrual periods. This is a serious disorder and is fatal for approximately 5 percent of affected individuals. Death is related to the extremely poor nutritional state of these patients; it may occur from heart failure or kidney failure, among other causes, and is associated with diseases afflicting the entire body. A physician’s supervision, psychological counseling, and behavioral modification are very successful in the improvement of patients with this disorder.

Bulimia nervosa is characterized by “binge-purge” cycles of rapid, uncontrolled eating followed by self-induced vomiting, the use of laxatives, and extreme dieting. For a diagnosis of bulimia, these episodes must occur at least twice a week for three months. In contrast to anorectics, bulimics are of normal to slightly above normal weight, so are not as often suspected of having an eating disorder. Bingeing and purging usually occur in private. Severe medical consequences of the behavior include cardiac arrest, rupture of the esophagus (the tube that runs from the mouth to the stomach), eroding of tooth enamel, and severe dehydration. As with anorexia, medical intervention and psychological counseling are necessary to control and defeat this harmful behavioral pattern.

There are other common physical complaints for adolescents during this period. “Growing pains” are a very real phenomenon during the rapid growth period of puberty. Sharp pains, especially in the legs, may sometimes awaken the sleeping adolescent. This discomfort is best treated with massage or a mild over-the-counter pain reliever. Pain associated with menstrual periods is common in adolescent, as well as adult, females. In most cases, over-the-counter medications provide relief, but in severe cases, or when pain is associated with heavy menstrual flow, a physician’s intervention is recommended.

Depression, a feeling of gloom and hopelessness about the present and the future, is a disorder that may afflict the adolescent. Many factors can provoke or heighten depression, including rejection by peers and/or parents, chronic illness, economic turmoil, severe family problems, and stress associated with school. Frequently, the situation quickly resolves itself, but if depression occurs for an extended period (for days or weeks, depending on the teenager), medical intervention and psychological counseling are recommended. Untreated depression can lead to eating and sleeping disorders, a desire to escape problems through the abuse of drugs or alcohol, severe behavioral problems, or psychosomatic disorders such as headaches, chest pains, stomach problems, and fatigue. Anxiety, unfocused fear that sometimes leads to extreme situations including panic attacks, is another psychological disorder sometimes associated with puberty. The most severe outcome of depression and/or anxiety is suicide. Any indication that a teenager is considering suicide, no matter how seemingly inconsequential, must be taken seriously; medical and psychological intervention must be obtained at once.

Perspective and Prospects

Extensive historical evidence dating back as far as the time of Aristotle (384-322 b.c.e.) suggests that the onset of puberty in modern times occurs much earlier than at most other periods of recorded history. Nevertheless, there are many exceptions to this trend. During times of severe stress—for example, in Western Europe during World War II—the age of onset of puberty was several years later than in calmer political times.

Many factors are responsible for the earlier onset of adolescence in Western societies, including improved nutrition and elevated economic status. Improved public health, in terms of immunizations to prevent and treatment to cure childhood diseases, likewise contributes to the improved health of the individual and onset of puberty at an earlier age. Modern society, however, creates stresses that in some cases delay the age of pubertal onset. These factors include poverty, the divorce and remarriage of parents, separation from siblings, and increasing responsibilities assigned to children whose parents are unavailable to the child for much of the day.

In cases of delayed puberty attributable to deficiencies in gonadotropin production or a failure of the gonads to mature despite adequate levels of gonadotropins, medical intervention can compensate for the resulting physical immaturity. Boys can be given increasing doses of testosterone over a period of time, which will lead to the development of the external physical traits characteristic of puberty. Girls initially may be given oral doses of estrogen and then be given a combination of estrogen and another sex hormone, progesterone, as therapy progresses. These hormones lead to normal external pubertal development in most cases.

Some individuals with delayed puberty are deficient in human growth hormone and also experience greatly shortened stature as compared with the normal range of heights for other individuals in their age group. Until the 1980’s, human growth hormone was isolated from cadavers, and its cost was prohibitively high for most people. With the revolution in recombinant DNA technology, human growth hormone is synthesized quite cheaply and is available to individuals who need it. Unfortunately, the accessibility of this drug creates the possibility of its abuse by parents who want their normal children to be exceptionally large and strong.

In the latter third of the twentieth century, psychologists and other health professionals began to recognize an increase in the rate of disturbed behavior exhibited by adolescents. These behavioral anomalies included alcohol and drug abuse, promiscuity (with the accompanying risk of infection with sexually transmitted diseases and/or pregnancy), depression, and suicide. Educators, health professionals, and concerned adults recognize these syndromes and address them through counseling, medication when indicated, outreach programs, and peer counseling programs, among other efforts. As the medical and psychological communities gain further understanding of the physical, psychological, and social consequences of puberty, additional interventions will be developed to smooth out this turbulent period of human development.


Adams, Gerald R., and Michael D. Berzonsky, eds. Blackwell Handbook of Adolescence. Malden, Mass.: Blackwell, 2006. A professional guide to this topic in the Blackwell series of developmental psychology titles.

Garrod, Andrew, et al. Adolescent Portraits: Identity, Relationships, and Challenges. 6th ed. Boston: Pearson/Allyn & Bacon, 2008. Stories written by teens survey myriad social issues that impact adolescents in the United States and illustrate theories of adolescent development. Topics include eating disorders, sexuality, family relationships, self-image, and dealing with illness.

Greydanus, Donald E., ed. Caring for Your Adolescent: Ages Twelve to Twenty-One. New York: Oxford University Press, 1997. An excellent resource for those interested in the physical and psychological changes that occur during adolescence. Included are chapters on compassionate parenting as well as specifics on the diseases and challenges commonly encountered during this period.

Kimmel, Douglas C., and Irving B. Weiner. Adolescence: A Developmental Transition. 2d ed. New York: John Wiley & Sons, 1995. A text on adolescent psychology that addresses the changes that come with puberty. Includes a bibliography and indexes.

Kroger, Jane. Identity Development: Adolescence Through Adulthood. 2d ed. Thousand Oaks, Calif.: Sage, 2007. Provides guidance on the many facets of development of self-image and personal identity through the teen years and beyond.

Santrock, John W. Adolescence. 13th ed. Boston: McGraw-Hill, 2010. A text that covers all aspects of adolescent development.

Steinberg, Laurence, and Ann Levine. You and Your Adolescent: A Parent’s Guide for Ages Ten to Twenty. Rev. ed. New York: HarperInformation, 1997. Designed as a parents’ guide to children aged ten to twenty, this clearly written book covers the physical aspects of puberty as well as the social, psychological, and health issues confronting adolescents.

Stepp, Laura Sessions. Our Last Best Shot: Guiding Our Children Through Early Adolescence. New York: Riverhead Books, 2001. Stepp shows readers the intricacies of teens’ lives, schools, friends, and families through case studies of twelve children in Los Angeles; Durham, North Carolina; and Ulysses, Kansas. This book is recommended for teachers, parents, and adults in the community.

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