• Menarche- time of first period which is about age 12.5
• Puberty- comes from the latin word pubertas meaning
adult, it is when one is capable of sexual reproduction.
It has three physical functions:
o Rapid increase in weight and height =growth
o Development of primary sex characteristics, the
o Development of secondary sex characteristics,
breast and pubic hair
• Hormones are present before birth where some
increase and others decrease
• No new hormones are produced
• Glands: organs that stimulate particular parts of the
body to respond in specific ways to particular
• Hormones carry messaged to particular cells in the
body, and similarly cells are designed to receive
hormonal messaged from particular hormones.
• When a hormonal level in your body dips below the
endocrine system’s set point, secretion of the hormone
increases, and when the set point if reached, secretion
• The set point can be adjusted according to
environmental or bodily conditions.
• Hormonal Feedback loop: Gonadotropin releasing
hormone neurons fire in the brain to increase a
• HPG- feedback loop involving hypothalamus, pituitary,
o Pituitary – controls hormonal level in general
o Hypothalamus- controls the pituitary gland, and
has a concentration of GnRH neurons
o Gonads- testes and ovaries, which release
androgen and estrogen present in both sexes in
different ratios/ levels. • The hypothalamus maintains levels of androgen and
estrogen, and once they fall below set point, it does not
inhibit the pituitary gland, thus allowing it to stimulate
the release of sex hormones from the gonads and the
• Adrenarche- maturation of adrenal glands that happens
before adolescence. The pituitary stimulates the thyroid
and adrenal cortex to secrete hormones that cause
body changes to take place at puberty.
• Heightened vulnerability to stress because the
hormonal changes of puberty make them more
responsive to stress.
• HPG axis is active before birth but is quiet until middle
childhood when puberty occurs.
• Puberty occurs only after a certain amount of body fat,
leptin is accumulated and can be delayed by stress,
illness, nutritional deficiencies, excessive exercise, and
• Leptin tells the hypothalamus to stop inhibiting puberty,
and GnRH neurons are activated.
• Hormones play two roles:
o Organization role- before birth, hormones organize
brain in ways that are not active until adolescence.
At 8 weeks, brain of a fetus is female by default
unless it receives testosterone .The sex
differences in brain organization predetermines
certain behavior, which does not appear until
later. Hormones program the brain in certain
o Organizational role of hormones: the process
through which early exposure to hormones
prenatally organizes the brain or other organs in
anticipation of later changes in behavior or
o Activational role of hormones: the process through
which changes in hormone levels especially at
puberty stimulate changes in the adolescent’s
behavior, appearance or growth. Somatic Development
• Individual grows 10 inches taller, brain changes in size,
structure and function.
• Adolescence growth spurt occurs with the release of
growth hormones, thyroid hormones and androgens
that increases the speed at which growth occurs.
• Peak height velocity: the time when the individual is
growing the fastest , at the same rate as a toddler.
• The conclusion of puberty is when the ends of the long
bones are closing = a process called epiphysis which
stops growth in height.
• Growth spurt occurs 2 years earlier for girls than boys.
• The increase in height results from an increase in torso
length rather than leg length. Extremities, the head,
hands and feets are the first to grow, then comes the
arms and legs and then torso and shoulder. Their body
is out of proportion because the parts of the body do
not grow at the same rate during puberty.
• Muscle tissue grows faster in boys than girls but body
fat increases more for girls than boys just before
puberty, and boys even decline in body fat before
puberty= the reason for sex differences in athletic
performance is due to hormonal imbalances because
androgen increases in males at a faster rate than in
females which influences growth.
• Sex differences in body fat can also result for
environmental factors such as little physical activity for
girls, and poor nutrition.
• Those who mature early, dating early, and come from
more affluent families start dieting early as well –
feelings of dissatisfaction. This differs b/w ethnicity
because black girls don’t diet are less vulnerable.
• Secondary sex characteristics: manifestations of
sexual maturity at puberty, including the development
of breast, facial and body hair and changes in the voice.
• Tanner stages: describes the 5 stages of pubertal
development/ secondary sex characteristics and sexual maturation is measured according to the tanner stages.
• It is in order for boys. It involves: growth of testes
and scrotum, pubic hair, growth spurt, growth of penis
and more pubic hair (darker colour). The are changes in
the skin, it becomes rougher, around the arms and
thighs and increased sweat glands which gives rise to
acne and pimples. Voice deepening occurs during late
adolescence. Breast development is influenced by the
estrogen hormone where the areola ( are around the
nipple) increases in size.
• Boys are capable of fathering a child/ fertile before they
look like an adult.
• It is less regular for girls. First, breast grows then
pubic hair, then body, and after menarche occurs. Then
underarm hair and sweat glands.
• The size of the breast does not matter in indicating
sexual maturation, it is the areolar and the nipple
growth that matters.
• Development of reproductive capacity includes growth
of uterus, vagina, enlargement of labia and clitoris.
• Ovulation follows menarche about 2 years after so girls
look mature before they are fertile or can be mothers.
Timing and Tempo of Puberty
• Timing and rate of maturation varies greatly b/w 7 in
girls and 9 in boys to 13 in girls and 13.5 in boys. An
early and fast maturing adolescent can complete
pubertal maturation way before a later mature and
before late and slow maturer.
• Late maturer- being somewhat taller
• Early mature- somewhat heavier
• The timing and tempo of an individual’s pubertal
maturation is largely inherited according to twin
studies. Environment’s role is that it determines exactly
when an individual goes through puberty while genetic
factors are predispositions thought of as an upper and
lower age limit. Environmental factors are nutrition and health. Puberty occurs earlier for those who are better
nourished at younger ages, but chronic illness or
excessive exercise can delay puberty.
• Puberty also occurs early for girls who grow up in a
household without a