Puberty in Adolescents


Puberty has been defined as "the biological changes of adolescence" (Steinberg, 1996) and "Biological developments [which] change boys and girls from physical immaturity to biological maturity" (Cole & Cole, 1993).

What changes occur during Puberty?
There are five main physical occurrences from puberty:

  1. Growth occurs
  2. Body composition begins to change.
  3. The circulatory and respiratory systems begin to change
  4. The primary sex characteristics develop
  5. The secondary sex characteristics develop

There is a great amount of variation in the rate of changes that may occur. Some adolescents may experience these signs of maturity sooner or later than others.  It is important to remember that these changes happen at different times for everyone.  Being smaller or bigger than other girls or boys is normal as each child experiences puberty at his/her own time. The following are the average ages when puberty changes may occur:  

Age of puberty: Females Age of puberty: Males
8 to 13 years of age 9.5 to 14 years of age



Physical Effects of Puberty

There are specific stages of development that both boys and girls go through when developing secondary sexual characteristics.  The following is a brief overview of the changes that occur in a girl: 

  • The start of puberty is signalled by the development of breast buds - medically termed thelarche. A small mound is formed by the elevation of the breast and papilla (nipple). The areola (the circle of different skin around the nipple) also starts to increase in size
  • Pubic hair begins to grow - medically termed adrenarche. The initial growth is soft hair covering  a small area around the genitals
  • There is a growth spurt - with the feet, arms, legs, and hands sometimes growing faster than the rest of the body. This may cause an adolescent girl to experience a time of feeling clumsy
  • The overall body shape begins to change as the hips get wider and the waist relatively smaller. There may also be an increase in fat in the buttocks, legs, and stomach
  • An increase in oily skin, sweating and acne may develop
  • The breasts continue to enlarge.   Eventually, the nipples and the areolas will elevate again, forming another projection on the breasts
  • Menstruation begins, medically termed menarche. The girl is now a young woman as she can become pregnant
  • Hair growth continues to increase, not only the pubic area, but also under the arms and on the legs.  Most young woman start to shave the later areas
  • The breasts reach their full adult state, only the nipple remains erect

The following chart shows the variations of physical changes at puberty, and the age range within which that change typically occurs:

Characteristics Age of Occurrence Characteristics Age of Occurrence
Sudden rapid body growth in height and weight 9˝ - 14˝ years Sudden rapid body growth in height and weight 11 - 16 years
Breasts start budding (first visible sign of puberty) 8 - 13 years Testes and scrotal sac grow 10 - 13 years
Pubic hair develops(shortly after breast development) 8˝ - 14 years Pubic hair develops 10 - 15 years
Menarche occurs 10 - 16˝ years Penis growth 11 - 14˝
Underarm hair grows About 2 years after pubic hair Underarm and facial hair About 2 years after pubic hair
Oil/Sweat glands develop Around time of underarm hair Oil/Sweat glands develop Around time of underarm hair
    Voice breaks (larynx grows) Around the same time as penis growth


Puberty and the teenage years are also termed adolescence.  During this time, the teenager will see the greatest amount of growth in height and weight. Adolescence is a time for growth spurts and puberty changes.  An adolescent may grow several inches in several months followed by a period of very slow growth, then have another growth spurt.  Changes with puberty may occur gradually or several signs may become visible at the same time.  The growth spurt triggers the legs to grow, followed by the body's trunk, and ending in the shoulders and chest.  Bones become harder and denser, while muscle and fat contribute to an adolescent increase in weight. 

The growth spurt usually occurs in girls about two years before boys and in many countries the average height of a 12-year old girl is similar or taller than the average 12-year old boy. 

Physiological Changes
During puberty, the body undergoes considerable changes in its composition, and in its circulatory and respiratory systems:

  • Girls develop breasts, acquire hips, and have a higher ratio of fat to muscle. Females are healthier, live longer, and are able to tolerate more long-term stress than males.
  • Boys develop wider shoulders, a more muscular neck, and lose fat during adolescence. Males develop larger hearts and lungs, have higher blood pressure, and lower resting heart rates than females.  Overall, males can exercise longer and with greater force than females.

The physical development of girls during puberty is described in the Tanner model:

The following diagram compiles several studies to show the average age at which American girls go through the various stages of puberty:

A UK study suggests that British girls are perhaps six months later, but conversely a South African study suggests that girls in that country are up to a year earlier.  The regional differences mean very little given a consistent finding that locally boys lag girls through puberty by one to two years.


Waist and Hips
One the most visually obvious changes at puberty is the hormone induced differentiation of the previously similar waist and hip shapes of boys and girls.

The Androgenic Body Form (genetically XY and passed through a testosterone dominant puberty) typically has:
  • Increased subcutaneous fat deposition along the abdomen and flanks
  • Narrow pelvic brims (see figure A below)
  • Lower body fat than estrogenic forms
  • A waist-to-hip ratio (WHR) of 0.85 to 0.95 for men of normal weight
  • The buttocks area has a ‘flatness’ or concavity (see figure C below)

The Estrogenic Body Form (genetically XX and passed through an estrogen dominant puberty) has:
  • A greater proportion of fat deposited on the buttocks and hips
  • Wider pelvic brims (see figure B above)
  • 10% more body fat compared to androgenic forms
  • A waist-to-hip ratio (WHR) of 0.65 to 0.80 for women of normal weight
  • The buttocks have a ‘fuller’ round shape (See figure D above)


Sexual Development

The sexual and other physical maturation that occurs during puberty results from hormonal changes. As the adolescent nears puberty, a gland in the brain called the pituitary gland increases the secretion of a hormone called follicle-stimulating hormone (FSH). This hormone then causes additional effects.  In girls, FSH activates the ovaries to start producing oestrogen. In boys, FSH causes sperm to develop.

Sexual development involves enlargement, maturity, and the reproduction of the primary sex organs.  The male testes produce sperm cells and the prostate gland produces semen.  Males are can ejaculate the semen, which contains the sperm.  The female ovaries release the mature ova into the fallopian tubes. Menstruation occurs if conception does not.

As the primary sex organs mature, the secondary sex characteristics distinguish males from females.

Female Sexual Development
Girls experience puberty as a sequence of events, but their pubertal changes usually begin before boys of the same age.  Each girl is different and may progress through these changes differently. 

Figure 1:
Changes during puberty, in girls.  (A) shows a typical girl before the onset of puberty; in (B) the breasts are beginning to develop and there is the beginning of pubic hair. There is also increased height and body fat. (C) shows a fully developed female figure at about age 16 or 17.

In girls, the first physical signs of sexual development are the budding of breasts, usually between ages 8 and 13.  Not uncommonly, one breast may begin to develop before the other, or the breasts will be asymmetrical.  While this may seem a cause for concern, it usually is not a sign of abnormality. Breasts are seldom exactly the same size, and by adulthood they have usually evened out, so the differences are barely noticeable.  If the breasts remain markedly asymmetrical or, in rare instances, one fails to develop, it can be a source of embarrassment and sensitivity.  A visit to a physician may assure a girl with asymmetrical breasts that she does not have a disease, and that the problem can be surgically corrected.

At the same time as the breasts develop or shortly thereafter, pubic and other body hair begins to grow.  As puberty progresses, girls experience an adolescent growth spurt and begin to accumulate body fat in an adult female pattern: rounded hips and buttocks and a further filling out of the breasts - during puberty the typical girl will add about 35 pounds (15kg) of "reproductive fat".  At the same time, vaginal discharge may increase, a sign of impending menarche, or the onset of menstruation.  By the time menstruation is established, the growth spurt is largely completed, although some girls add an inch or two in height after menstruation begins.

The average age of menarche in the United States and other Western countries is now about 12.5 years, although menarche at any time between the ages of 8 and 16 is considered normal. While the age of menarche has been declining by about 8 months per generation since the turn of the century, this decline appears to have largely ceased.  The reasons for the younger age of menarche are unclear, but improved nutrition is believed to be a major factor. Studies have found that when a girl of average height reaches about 105 pounds, menstruation shortly follows. The percentage of body fat is also believed to be a factor, presumably because a certain amount of fatty tissue is needed for the hormonal changes initiating menstruation. The fact that ballet dancers, long-distance runners, and other girls with low percentages of body fat generally experience menarche at a somewhat later than average age supports this theory.

The onset of menstruation does not necessarily coincide with the beginning of ovulation.  Many teenage girls experience irregular and/or very heavy periods for the first year or two—possible signs of absent or irregular ovulation.  This is not abnormal but a sign that while enough female sex hormones are being produced to cause a proliferation and shedding of the uterine lining, not enough pituitary stimulating hormone (FSH and LH) is being secreted to result in regular ripening and release of an egg from one of the ovaries. Within 1 or 2 years of menarche, however, most girls ovulate with some degree of regularity.

Male Sexual Development

Figure 2: Changes during puberty, in boys.  (A) shows a boy at about age 9 before the onset of puberty. In (B) secondary sex characteristics are beginning to develop; e.g., the beginning of pubic hair and enlargement of the penis and testes. There is also increased height and muscle development. (C) shows a fully developed male at about age 18.

Boys generally enter puberty about a year later than girls, i.e. between the ages of 10 and 14.  The first physical signs are growth of the testes and penis, accompanied or shortly followed by the appearance of pubic and other body hair.  About two years after puberty begins there is significant growth spurt - many 12-13 year-old girls are similar in size and weight to boys of the same age, but are then rapidly overtaken.  During the growth spurt, breast tissue may develop in up to two-thirds of adolescent boys, but this usually disappears in about 6 months (although in some it may persist for a year or longer).

The torrent of 'male' testosterone hormones on the pubertal boy trigger significant changes to their larynx, causing a deepening of the voice and the growth of an "Adam's apple".  There is stimulation of facial hair that begins with a moustache and within a few years extends over most of the lower face.  The rising testosterone levels also causes an increase in muscle mass - in particular the biceps, shoulder and thigh muscles all grow larger and stronger than in girls.

Ejaculations generally begin sometime between the ages of 11 and 15, although anytime between the ages of 8 and 21 is considered normal.  Ejaculation may occur during sleep or in response to masturbation or a sexual fantasy.

Although the major events of adolescence in boys are usually completed by the age of 17 or 18, growth may continue (albeit at a slower rate) until the age of 20 or 21.

Hormones and Adolescents

What are Hormones?
Hormones are a specific organic product of living cells that, transported by body fluids, produces a specific effect on the activity of cells remote from its point of origin. 

The human endocrine system consists of glands (adrenal, thyroid, pituitary, pancreas, ovaries, testes) that manufacture & release hormones into the bloodstream.  Hormones are vital chemical messengers that instruct target organs to perform or cease to perform actions that are vital to life, e.g., normal growth, proper metabolism, spermatogenesis (in men), periodic ovum release (in women).  The endocrine system produces, moves, and adjusts levels of hormones in the body. Hormones are very specific substances secreted by one or more endocrine glands.  Because receptors in our cells respond to some hormones and not to others, the action of each hormone is unique.  Hormones influence organs throughout the body, and regulate growth and many other aspects of normal body function. 

Maddie Whitley started taking oestrogen hormones when age 14 and was soon "wearing a really big sweatshirt all the time to hide my new boobs".  Pictured age 17 after transition.

Androgens are a class of hormone, found mainly in males although also in females, of which testosterone is the most important.  Manufactured in the testes of men (and in the adrenal cortex & ovaries of women), testosterone is responsible for the differentiation of male & female primary sex characteristics at about the 7th week of foetal life.

Oestrogens are thought of as female hormones and androgens are thought of as male hormones, both types are present in each sex, but in different amounts.  Hormonal activation may influence excitability, arousal, or emotionality.  These in turn may influence how individuals behave.

The hypothalamus responds to the levels of sex hormones within an adolescent's body.  When the endocrine system levels of oestrogen and androgen fall, the hypothalamus stimulates the pituitary gland to release sex hormones through the gonads.  The gonads are the ovaries in females and testes in males.  The sex hormones stimulate the females' ovaries to produce oestrogen and progesterone.  This stimulation triggers the release of mature ova from the ovaries to allow for future reproduction.  These hormones also stimulate the testes and adrenal glands among males.  This stimulation produces the hormone testosterone for producing sperm.  Puberty begins when the hypothalamus is signalled, and the pituitary gland is activated. 

levsl in Women

Testosterone levels
in Men

The changes in hormone levels at puberty are dramatically different between boys
and girls, unsurprisingly this results in dramatically different physical changes.

Males and Hormones:
A young transsexual girlAt puberty a boy's testes start releasing large quantities of the androgen testosterone, which leads to muscle growth, body and facial hair, and other male sex characteristics.  Testosterone also contributes to gains in body size.  The production of hormones is associated with emotionality, specifically aggressive behaviour in boys.  These effects may be greatest when the endocrine system is being turned on.

Testosterone is responsible for the differentiation of the central nervous system (mainly the hypothalamus) into male and female types with regard to the different reproductive cycles and functions.  Males also receive major surges of testosterone at puberty so that the task of sex differentiation can be completed - oestrogen surges occur at that time in females.

Testosterone is responsible for the development of secondary sex characteristics in males such as pubic & facial hair, deepening of the voice, & ability to ejaculate sperm-laden semen.

Androgens are also responsible for baldness. 

Females and Hormones
Oestrogen is responsible for menarche & breast development.  Oestrogen released by a girl's ovaries cause the breasts, uterus, and vagina to mature and the body to take feminine proportions.  In addition, oestrogens contribute to regulation of the menstrual cycle.  Girls also are affected by androgens secreted by the kidneys for their growth spurt, underarm and pubic hair.  The production of hormones is associated with emotionality, both depressive and aggressive affects in girls.  These effects may be greatest when the endocrine system is being turned on.

A young girlHow do Hormones affect adolescents and his/her transition into adulthood?
Despite the advance of feminisism and sexual equality, there is still (correctly or incorrectly) often perceived to be a great difference between the role of boys and girls, in the so called "Western Societies"  For boys, puberty is believed to expand role possibilities into the realm of work and achievement.  Girl's roles are believed to be confined, even on the eve of the 21st century a writer suggested: "Boys are classified as Doing and girls are classified as Being".  Girls may be more vulnerable to problems with autonomy, a sense of oneself as a separate self-governing individual, than boys may.  Girls have been characterized to be more emotionally focused and less individualized the identity status of self-chosen values and goals, from their mothers than boys do.  Girls are more interpersonal, intimate, and relationally focused.  Girls tend to be more intimate while boys may develop intimacy problems or become more salient at Puberty.  Emotional health, depression, conduct disorders, and eating disorders are all linked to gender.

A young transsexual girlA common belief is that pubertal change has something to do with adolescent moodiness and the desire for greater physical and emotional separation from parents.  Indeed, higher hormone levels are suspected to be related to greater moodiness, in the form of anger and irritability for males and anger and depression for females, between nine and fourteen years of age.  Studies indicate that low points of mood swings are associated with time spent with friends and in self chosen leisure and hobby activities while high points tended to occur in adult structured settings- class, job, school halls, school libraries, and church.  These finding suggest that situational factors may act in concert with hormonal influences to affect teenagers' moodiness.

Biological as well as social plays an important role.  Early maturation in boys appears at more of an advantage in many aspects of emotional and social functioning.  Adolescent boys are viewed as relaxed, independent, self-confident, and physically attractive.  Late maturing boys are viewed as anxious, overly talkative, attention seeking in behaviour.  Among girls the impact of early versus late maturation is just the opposite.  Early maturers are below average in popularity, appeared withdrawn and lacking in self-confidence, and held fewer positions of leadership roles.  Late maturers are regarded as physically attractive, lively, sociable and leaders in school.

In conclusion, it is safe to say that hormones and their effects on adolescents vary with age and gender.  Not every transition into adulthood will be easy, but to enhance and help adolescents cope with all the chemical changes taking place, one needs to be supportive, understanding, and patient to all trial and errors.

Jamie (left, shown age 23) and Chloe O'Herlihy (age 20, formerly Daniel).  Jamie became unsure about her gender age 14 her and when she finally transitioned and began hormones age 22, her younger brother did the same.

Brothers to Sisters
"Brothers who became sisters" was a hot topic in the Psychology press during the 1980s.  There is at least one recorded instance of three brothers becoming sisters.

While transsexual sisters are very rare, they are also far less rare than might be expected if we accepted (for example) that 1 in 2000 male babies suffer from gender dysphoria on a random basis.  Other biological and sociological factors seem to come in to play, and this remains a source of medical interest.

16 year old Kim Petras, formerly Tim.  Pictured just after her SRS, following four years of hormone treatment.


Effects of Hormone Treatment on the Transsexual Male-to-Female Boy/Girl
Ideally, in order to maximise the physical benefits, low level oestrogen treatment of the young transsexual boy-to-girl should begin at age 8-9 years.  Before the onset of male puberty (at about age 11, but can vary by 2 years) a bilateral orchiectomy (castration) should be performed to remove both testes and hormonal treatment then increased to induce a female type puberty age 10-11.  The results are usually extremely successful, with many clearly female aspects (e.g. limited muscle growth  and flattering fat deposits) resulting as the child moves to adulthood, whilst avoiding clearly male aspects (e.g. broken voice and facial hair).  However, even in this best possible case, it's impossible to totally overcome the combination of XY chromosomes and a hormonal legacy dating back to the womb, with typical results still being above average shoe size and below average bra size for a woman.  

For much more information about the female hormone treatment of the young transsexual see this article.


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Last updated: 27 September, 2012

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