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).
changes occur during Puberty? 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:
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:
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 following chart shows the variations of physical changes at puberty, and the age range within which that change typically occurs:
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.
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
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 producingoestrogen. 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.
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.
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
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.
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.
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
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 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
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
Hormones and Adolescents
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.
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.
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.
affect adolescents and his/her transition into adulthood?
A 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.
Brothers to 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.
Effects of Hormone Treatment on the Transsexual Male-to-Female
For much more information about the female hormone treatment of the young transsexual see this article.
Back to Articles
Last updated: 27 September, 2012