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IB 140 part 6
Terms in this set (74)
-early sexual maturation around 6-8 years old
-induce body odor, oily skin, cognitive development, height growth
-maturation and increased activity of adrenal glands
-result of development of zona reticularis of adrenal cortex which secretes androgens but not cortisol levels
zones in the adrenal gland
cortex and medulla
zones in the cortex
zona glomerulosa, zona fasciculata, zona reticularis
Biological transformation that
takes a person from being a sexually
immature child to a sexually mature,
reproductively fertile adult.
State of the child between
the onset of pubertal changes and the
completion of sexual maturation.
The socially defined period
of youth between start of puberty and
Female pubertal process
-Females on average begin their growth spurt
two years earlier(~9 years old) and become fertile one to
two years earlier than males
-Upon completion of puberty, females have a
higher % of their body weight consisting of fat
Tanner stages on female breast development
2: breast and papilla (nipple) elevated as a small
mound and areola diameter increased
3: breast and areola enlarged; no contour
4: areola and papilla form secondary mound which
produces a contour separation with rest of breast
5: nipple projects and areola becomes part of
general breast contour
Tanner stages on female and male pubic hair
1: prepubertal with no hair
2: sparse, lightly pigmented, straight hairs
3: darker hairs that start to curl with
increased amount of hair
4: course, curly, abundant hair but not as
much as adult hair
5: adult distribution of hair often with spread
to medial surface of thighs
Tanner stages of male genitalia
1: prepubertal, testicular size less than 2.5 cm
2: enlargement of scrotum and testes, scrotal skins reddens and changes in texture, 2.5-3.2 cm long
3: enlargement of penis, further growth of testes, 3.3-4.0 cm long
4: increased size of penis with growth in breadth and development of glans, testes and scrotum larger, scrotal skin darker, 4.1-4.5 cm long
5: adult genitalia, greater than 4.5 cm long
female puberty at 9 years
-accelerated skeletal growth rate with increased
-Increased fat deposition begins
female puberty at 10 years
-early breast development
-growth and widening of the bony pelvis from
• fat deposition in hips & breasts
female puberty at 11 years
-Ovaries and female sex accessory structures
(oviducts, uterus, vagina) grow & mature
female puberty at 12 years
female puberty at 13 years
-skeletal growth rate declines
-sweat & sebaceous skin glands develop
-acne may develop
sign of puberty in females
-12.3 years average age in USA
-13 years average age in Europe and Canada
female puberty at 14 years
female puberty at 15 years
-reach adult height
-high levels of estrogen halts leg bone growth
puberty and pelvic bone maturation
-Female pelvis reaches full final size at
least 4 years after menarche and is
last part of skeletal structure to mature
-Full maturity of pelvis is typically
completed by 17-18 years of age, and
this appears to be somewhat
independent of the age of menarche.
precocious puberty in females
-Breast development and/or pubic
hair growth occurs before age 7
-Average time of onset of breast
development and/or pubic hair
growth is 10 years of age, so a
female with precocious puberty
develops these characteristics at
least three years earlier than
delayed puberty in females
No breast growth by age
14 or no skeletal growth
spurt by age 15
Primary amenorrhea and causes
-female who has not
menstruated by age 16
-low body fat content, e.g., from extreme
exercise, anorexia nervosa, or other forms
male puberty at 9 years
-Initial stages of spermatogenesis
-Leydig cells appear and began to
male puberty at 10 years
testes to begin to enlarge and increased subcutaneous fat deposition
male puberty at 11 years
-skeletal growth spurt to begin
-Increase in scrotum and penis size
-Increase in spontaneous erections
-Growth of seminal vesicles & prostate gland
male puberty at 12 years
Pubic hair development
male puberty at 13 years
-Hair appears in axilla and on upper lip
-Voice deepens from larynx growth
male puberty at 14 years
first fertile ejaculation = spermarche
male puberty at 15 years
sweat and sebaceous glands to develop, including acne development
male puberty at 16 years
accelerated muscle growth and strength and broadening of shoulders
male puberty at 17 years
reach adult stature
Precocious puberty in males
Sexual development before age 9 years
Delayed puberty in males
No testicular growth has has occurred by age 14 or no skeletal growth spurt has occurred by age 18
testicular development at birth
-pair of testis already descended into scrotum
-seminiferous tubules of testes contain spermatogonia and Sertoli cells, but no sperm are produced
-Leydig cells of testes have been active during fetal period, but only a small number are present at birth
testicular development at 6 months
Leydig cells of testes are nearly absent
testicular development at 9-10 years
-Leydig cells again are visible
-spermatogenesis begins in the seminiferous tubules
-mature spermatozoa are not yet produced
-testis enlarge markedly by 10 years of age
testicular development at 14 years
mature spermatozoa are produced = spermarche
testicular size at 1 years
testicular size at 8 years
testicular size at 10 years
testicular size at adult male
Cryptochordism and percentages
-testes fail to descend into scrotum by birth
-3-4% at birth
-0.8% by 1 year
-0.3% by 10 years when spermatogenesis should occur
-Prevents spermatogenesis and causes
sterility because of temperature
damage, but Sertoli and Leydig cells
-Can develop into cancerous tissue
-If treated surgically in early childhood,
the testes can be normal
hormones during puberty in both sexes
-Growth hormone is secreted at higher
amounts during puberty
-Growth hormone and androgens are
responsible for growth of long bones and
other tissues during puberty
-Thyroid hormone increases with puberty
which supports body growth and results in
a rise in metabolic rate in both sexes
FSH & LH from birth to puberty
-Fetus & neonate: high levels
-1-8 years: low levels
-9-12 years; levels rise, first FSH and then
LH, and this happens two years earlier in
females compared to males
-LH pulses need to be every 1-3 hours and
of large amplitude for puberty to occur
pubertal hormones in females
-Sudden surge of LH, and to lesser extent,
FSH, results in menarche
-The first surge resulting in menarche may
not be sufficient to cause ovulation, but
enough cycle variation in ovarian estrogen
to cause menstruation
-Typically within several months of
menarche, the LH surge is large enough to
cause the first ovulation
Estradiol and estrone from and produced in
-Estradiol is from growing follicles in ovary
-Estrone is produced by body fat
-Mammary gland development
-Bony pelvis growth
-Subcutaneous fat deposition
-Growth of external genitalia
-Growth of vagina, oviduct, and uterus
pubertal androgens in females
-Levels of weak androgens,
dehydroepiandrosterone (DHEA) &
androstenedione are increased during
-These weak androgens are produced
by adrenal glands.
Pubertal adrenal androgens in females
As puberty progresses, weak androgens,
DHEA & androstenedione produced by
adrenal gland cause:
• Growth of pubic and axillary hair.
• Slight lowering of voice.
• Sebaceous gland & acne development.
• Long bone growth.
• Increase sex drive.
• Weak androgens arrive at certain target
tissues and are converted to testosterone
which then makes tissues grow & mature
Congenital adrenal hyperplasia
-Most common form of this disease is due to lack an enzyme (21-hydroxylase deficiency) needed by the adrenal gland to make hormones cortisol and aldosterone
• Without the enzyme, the body produces more androgen which causes male characteristics to appear early in males and inappropriately in females
• Females with congenital adrenal hyperplasia have an enlarged clitoris, which at birth may be large enough to look like a penis representing an example of ambiguous genitalia
Pubertal hormones in males
Increase in secretion of LH & FSH
in males at around 10 years of
age is responsible for:
• onset of spermatogenesis
• rise in testosterone secretion
Pubertal androgens in males
Testicular androgens & adrenal androgens in males cause:
• Sex accessory structure growth (seminal vesicles, prostate gland, penis, scrotum).
• Secondary sexual characteristics growth (pubic, axillary, & facial hair; larynx growth).
• Retention of nitrogen, calcium, and phosphorous which supports bone and muscle growth.
• Penis growth & touch sensitivity enhancement.
• Male sex drive enhancement.
Pubertal estrogens in males
• Blood estrogen levels rise slightly in
males before and during puberty.
• Sertoli cells in testis are likely source.
• Some males exhibit slight growth of
mammary glands during puberty,
which typically manifest as a small 1-2
cm lump under the nipple, which
resolves by the end of puberty.
Androgens and acne
• Rising androgens levels during
puberty in both males and females,
increase secretion of skin's sebaceous
• These glands can become clogged
and infected with bacteria, producing
acne on the face, chest, and back.
• Acne typically resolves by adulthood,
but can persist in some adults.
steroidal feedback at puberty
• Sensitivity of hypothalamus to steroidal
negative feedback on GnRH decreases
as puberty approaches.
• Hypothalamus of children (infant to 9
years of age) is 6-15 times more
sensitive to steroidal negative feedback
than that of adults.
• Positive feedback of estrogen on
GnRH is NOT present in children.
GnIH in hypothalamus
• Fibers from GnIH neurons have been
demonstrated to contact GnRH
neurons directly in hypothalamus.
• Injection of GnIH decreases firing rate
of GnRH neurons
• Evidence indicating that GnIH can also
inhibit the GnRH surge center
GnIH and stress
• This helps explain why stress can result in females not ovulating even if they have
adequate body fat for ovulation.
• Stress which increases GnIH could also
potentially cause some females to have a
delay in menarche/puberty even if they
have adequate body fat.
GnRH and GnIH at puberty
• The GnRH pulse generator appears to be
under inhibition from the brain during
• This inhibition is lifted at puberty.
• Future research will likely reveal that GnIH plays an important role in inhibiting activity of GnRH from infancy through childhood up until the onset of puberty.
• Hence, the activity of GnIH likely drops just before puberty.
females and estrogen feedback
• At puberty, females (but not males)
develop positive feedback of estrogen
on GnRH release resulting a surge of
LH and FSH secretion that can induce
• This positive feedback effect is NOT
present in female children, male
children, pubertal males, or adult
• The appearance of positive feedback
of estrogen on GnRH in pubertal
females appears to be the result of the
maturation of hypothalamic GnRH
surge center and/or the ability of the
pituitary to synthesize and store
adequate amounts of gonadotropins
melatonin and menarche
• Melatonin levels drop
significantly before the onset of
light and menarche
• Darkness increases the synthesis and
secretion of melatonin, which may
inhibit reproductive function.
• Light has the opposite effect.
• Some scientists believe that the steady
increase in exposure to artificial light
during the night may be contributing to
the earlier onset of menarche.
• hormone produced by the brain that stimulates release of GnRH with increased production of LH & FSH and steroidal hormones.
• contributes to the onset of puberty.
• neurons secrete kisspeptin into the arcuate nucleus region of the hypothalamus.
• Kisspeptin fits into GPR54 receptors.
• Studies in humans showed that men infused with intraveneous kisspeptin produced high amounts of LH, FSH, and testosterone.
kisspeptin studies in animals
• Plays a role in coordinating seasonal
reproduction in wide range of animal species.
• Connects environmental change with
• In certain animals, if the environment is not satisfactory, sex drive declines & vice versa.
• For example in some rodents, the kisspeptin levels and sex drive are high in the summer and very low in the winter....the sex drive appears to be modulated by kisspeptin.
• The monestrous cycle of animals (e.g., deer) is likely influenced by kisspeptin.
• protein produced by fat cells.
• In males and females, blood leptin levels increase just before the onset of puberty.
• A threshold level of leptin appears to have a permissive effect on puberty.
• Leptin increases the rate of GnRH pulses.
• Humans lacking the ability to produce leptin or its receptor may fail to enter puberty.
• Malnourished females (e.g., with anorexia nervosa) have a very low leptin levels.
• Overweight females have higher leptin levels and enter puberty earlier than normal weight females.
environmental factors and puberty
• Social interaction
• Environmental molecules
age of menarche in usa
• Age of menarche in females has
shown a steady decline worldwide, at
a rate of about 3 months per decade
over the last century
Average age of menarche in USA
• 1900 = 14.2 years.
• 1990 = 12.3 years.
age of menarche in europe
• Age of menarche has decreased by 4 years over the past 200 years in Europe while the extrinsic mortality rate has fallen and the likelihood of surviving to 15 year has increased
• This is attributed to better nutrition and
reduced infections which have resulted in
improvements of maternal and child health.
age of menarche factors
• Improved nutrition and access to food.
• Less physical activity & more weight
• Increased exposure to xenoestrogens
e.g., certain pesticides and plastics
fetal and childhood nutrition on age at menarche
Comparison of four different scenarios with earliest to latest menarche:
• light at birth and heavy at 8 years.
• heavy at birth and heavy at 8 years.
• light at birth and light at 8 years.
• heavy at birth and light at 8 years.
This comparison demonstrates the interplay of fetal and childhood nutrition in determining the age at menarche in Australian females.
• Light birth weight is associated with earlier menarche
• Heavier weight at eight years of age is
associated with earlier menarche
nutrition and weight at late childhood on age of menarche
• Deficient nutritional intake and low
weight in late childhood are cues to
delay menarche until metabolic and
nutritional conditions are more
• Overabundance of nutrients and fat
stores in late childhood are cues to
proceed into early menarche.
nutrition and menarche
• Anorexia nervosa or other types of poor/
malnutrition are associated with low body fat and delayed puberty.
• Evidence that female must have at least 17% of body weight as fat for sexual maturation to commence and at least 22% for menarche to occur and normal menstrual cycles to continue.
• Obese females produce estrone from their adipose tissue and this contributes to the estrogen load resulting in them reaching puberty at an earlier age than normal weight females.
adoption and menarche
• Children from tropical countries who are adopted by families in Europe tend to go into puberty significantly earlier.
• Female infants and children from India who were adopted by Swedish families experience menarche 1.4 years earlier than Swedish girls and 2.5 years earlier than Indian girls who remained in India.
• Children from tropical countries adopted into Danish families were 10-20 times more likely to undergo precocious puberty compared to Danish children.
• Yet children migrating from the tropics WITH their genetic families to Europe did not show an increased risk of precocious puberty, thus excluding an effect solely from migration.
• It appears that rapid changes in dietary
patterns and growth are contributing factors to development of early puberty in these children.
• Psychosocial stress experienced by many of these children in their home country prior to being adopted may have triggered a predictive adaptive response which contributed to the development of early puberty.
stress and menarche
When compared to girls in relatively conflict-free, two-parent households, young girls with excessive parental conflict, parent-child conflict, or absence
of genetic father and presence of a stepfather demonstrated the following traits:
• Reach menarche 5 months earlier.
• Pass through puberty stages more quickly.
• Have children at an earlier age.
• Spent less effort and time with their children.
• Formed less stable bonds with their partners.
• Studies suggest that psychological and
social stress during the from birth to 7
years of life accelerates sexual
maturation in females
• However, psychological and social
stress that commences around 8-11
years of age can cause a delay in
sexual maturation in females
genetics and menarche
• Age at menarche tends to be similar for
mothers & daughters.
• Identical twins menarche is typically within two months of each other.
• Variant of the gene CYP3A4 influences the enzyme that breaks down testosterone.
• Lower ratio of testosterone/estrogen results in earlier initiation of sexual development in females.