Class 5,6 - Puberty Flashcards
Puberty has three chief physical manifestations
- Rapid acceleration in growth, resulting in dramatic increases in height and weight
- Development of primary (present at birth) sexual characteristics, including gonads (sex glands) which result in hormonal changes
- Development of secondary (emerge within pubeirty) sexual characteristics, (changes in genitals, breasts, pubic, facial & body hair)
Four Points on growth chart
(1) Menarche is the last sign of puberty
(2) Boys lag behind girls
Wide variations in onset
(3) – Early as age 5 (girls) and age 6 (boys)
– Late at age 13 (girls) and age 13.5 (boys)
(4) Wide variation in duration
– Girls: 1. 5 to 6 years
– Boys: 2 to 5 years
thelarche
Breast buds - 10.5
pubarche
Pubic hair
girls - 11
boys - 12.5
Peak Height Velocity
girls - 11.5
boys- 13.5
Menarche
12.5
Spermarche
12-14
Testicular growth
Penis growth
11.5
12
Growth during childhood is
relatively stable
girls grow slightly faster than boys untill __
Then both genders average about __
~4 years
average about 5-6 cms/year and 2.5 kgs/year until puberty (i.e., about 2 inches and 5 lbs)
General rule of thumb about child growth
A child grows 10 inches in first year of life
About 5 inches in the second year (or ½ of first year)
Then about 2.5 inches/year until puberty
as puberty approaches—before sudden acceleration - growth takes a __
preadolescent dip
peak height velocity girls vs boys
Girls average a PHV of 9 cm/yr (3”) at age 12 and a total gain in height of 25 cms (or ~10”)
Boys attain a PHV of 10.3 cms/yr (4”) at age 14 and gain 28 cms (11”) in height during pubertal growth period
Pubertal growth accounts for ___of adult height
20%
Boys tend to be taller than girls before age __
Then girls taller between ___
than boys at__
11
Then girls are taller between 11-13
Boys overtake them by age 14
Height gain results more from increase in ___ length vs.___ length
torso vs leg
Sequence of puberty growth
Sequence is fairly regular
Extremities (head, hands feet) first to show growth
Then arms and legs
Then torso and shoulders
Pubertal growth accounts for___of adult weight
50%
peak weight velocity
In boys, PWV occurs at about same time as PHV (age 14) and averages 9 kg/year (i.e, ~20lbs/year); more bone/muscle than fat
In girls, peak weight gain lags behind PHV by about 6 months and reaches 8.3 kg/year (~18lbs) at about 12.4 more fat than bone/muscle
Sex Differences in Body Composition before puberty
Few sex differences in muscle development and only slight differences in body fat
Sex Differences in Body Composition during puberty
Muscular tissue grows faster in boys vs. girls
Body fat increases more in girls vs boys
Boys: muscle to fat ratio: 3:1
Girls: muscle to fat ratio: 5:4
Sex differences in strength & athletic ability appears in
about half of sex differences in athletic performance is simply result from
early adolescence
differences in body fat
Who is most susceptible to be overly concerned about weight—even if in the normal range (prompted by rapid increases in body fat prompts girls)
Girls who mature early & begin dating early
Girls who spend a lot of time talking about looks with their friends
Who are teased about their weight (by boys)
Who are pressured to be thin
Is mass media’s excessively positive portrayal of of thinness to blame? for girls being overly concerned about weight—even if in the normal range
yes but also friend talk is also to blame
also weight concous (also talk with girls who do the same) Co-Rumination and Selection & Socialization
Co-Rumination
It is comparing themselves with friends & not just media exposure that leads to unhappiness about body image
Selection & Socialization
Girls who are especially weight-conscious often hang around with peers who share the same concerns
North & South America, Europe and Asia
There is strong pressure for girls to be thin in many cultures,
less vonurable to feelings of body disfatsfaction
black teenagers, Less likely to diet, Ethnic differences in conceptions of ideal body type
two main biological processes of puberty
gonadarche - Pubertal maturation linked to increased activity of gonads (testes, ovaries)
adrenarche - Pubertal maturation linked to increased activity of adrenal glands
Gonadarche
“True central puberty”
Driven by Growth & maturation of gonads
(Ovaries in girls & testes in boys)
Increased production of sex steroids, e.g., estradiol & testosterone
stimulated by Pituitary gland releases gonadotropin hormones
gonadotropin hormones
Luteinizing hormone LH
Folic stimulating hormone FSH
Gonads respond by growing & releasing sex steroids T & E
But what triggers the pituitary gland to release gonadotropin hormones
Hypothalamus- stimulating Gonadotropin Releasing Hormones
GnRH (facilitated by Kisspeptin (Metastin))
Hypothalamus
Monitors hormone levels via regulation of pituitary
Triggers production of kisspeptin which causes a cascade of pituitary activity resulting in LH and FSH
production of kisspeptin afftected by
leptin and melatonin
leptin
Stimulates kisspeptin
Protein produced by fat cells
Regulates hunger & appetite
Signals brain that we are “full enough” and “fat enough”
melatonin
Suppresses kisspeptin
Regulates sleep cycle
more likely to go through puberty earlier
The more fat cells, and the more light to which one is exposed
Alternatively…a thin person not exposed to much light will go through puberty later
Overweight children have more body fat & produce more leptin, which stimulates kisspeptin
Kids exposed to more light (e.g., live near equator) have lower melatonin, so kisspeptin is not suppressed
Exposure to artificial light could have same effect (computer screen time?)
Gonadarche sequence
HPG Axis
Hypothalamus (GnRH) -> Pituitary gland -> Gonadotropin hormones (LH and FSH) -> Gonads
(testes and ovaries) -> Sex steroids (T and E)
HPG Axis is also activated in fetal development
and up to 6 months after birth for boys 12-24 months after birth for girls
Yielding “pubertal” effects Infants born with hair and boys getting erections
Followed by the “juvenile pause” (HPG goes offline)
Gonadal Hormonal Changes: Girls
FSH & LH stimulate sex steroid Estradiol (E) (E responsible for Female reproductive systems: Breast development, Body fat distribution, Ovaries (also produce Testosterone: Clitoris, Pubic hair, Bone growth, growth spurt)
E increases ~9-10, continues through 12-14, with occasional accelerations
Irregular cycles of LH & FSH & E about 18 months before menarche; irregular until 12-18 months after menarche
Gonadal Hormonal Changes: Boys
FSH & LH stimulates production of T
T starts to rise in response to sleep increases of LH around age 10
6 months later daytime concentrations of T increases
T concentrations can increase as much as 20 times, with greatest increases 12-14
E also present in boys, albeit at lower levels (Associated with growth velocity)
Adrenarche sequence
HPA axis
Hypothalamus (GnRH) -> Pituitary gland (Gonadotropin hormones (LH and FSH) ) -> Adrenal gland (DHEA, DHEAS, Androstenedione)
Adrenal Sterioids in boys vs girls
DHEA, DHEAS, “Andro”)
In boys
DHEA & DHEAS increases about 8-9, then andro 1-2 years later
In girls
DHEA and DHEAS increases evident as young as age 6, then andro 1-2 years later
Adrenal Sterioids body changes
Responsible for pubic hair (“pubarche”)
And changes in sweat glands (“odor”)
And sebaceous glands (“oily”)
Pubic hair, body odor and acne are obvious signs of puberty, but….
adrenarche and gonadarche are __
are independent processes governed by different mechanisms (seen by addisons and turners)
Addison’s disease
Adrenarche is largely absent (e.g, no pubic hair)
but gonadarche is unaffected
Turner’s Syndrome
Will experience adrenarche but not true gonadarche
Defective gonads (ovaries)
linked to 1st stirring of sexual attraction
Adrenal steroids (DHEA)
spike in late childhood (by age 10 for boys & earlier for girls)
Adrenarche may be govenring attraction
Gonadarche may be governing reproduction
What Drives Pubertal Maturation?
Biological Factors (Body Weight/Mass, Energy Metabolism, (Secular Trend))
and Socio-Behavioral Factors (Risk Behavior, Family dynamics)
Weight (Biological Factor in pubertal maturation)
“Frisch-Revelle Model”
“Critical weight” hypothesis 47-48 kg (104-106 lbs) - trigger onset of puberty
Overweight prevalence higher in early maturing girls
Being overweight doubles odds of early maturation
BMI (Biological Factor in pubertal maturation)
Girls with excessive BMI more likely to show advanced breast development at age 8-9
Pubarche more prevalent at ages 8-10
Menarche more prevalent 10-12
Elevated BMI associated with greater odds of thelarche, pubarche & menarche among younger girls (Leptin hypothesis)
Energy Metabolism (Biological Factor in pubertal maturation)
“Energetics Theory” or Life-History Theory
Natural selection favored a mechanism that allows us to track availability of energy resources in early childhood & alter trajectory of development
Brain detects that availability of metabolic fuels (calories) is outpacing body’s demand for energy
Trade-off between growth & reproduction
Poor access to food during early childhood is a signal to delay puberty and development of reproductive systems
Calorie rich early environments associated with accelerated pubertal maturation
may explain secular trend
Age of menarche has dropped___ each decade
1840s-1960s
4 months
Secular trend largely absent in “3rd-world” societies
Prominent explanation __
Secular trend largely absent in “3rd-world” societies
Prominent explanation: Access to calories
Delayed menarche in girl athletes
irregular menses or amenorrhea
Each year of training before menarche could delay onset by 5 months
secular trend
dramatic downward shift in age of monarchy
Pre-pubertal alcohol and tobacco use disrupts ___
the endocrine system and alters the timing of pubertal development (breast development)
Risk Behavior (Socio-Behavioral Factors in pubertal maturation)
Girls who use alcohol before puberty had 4 times the odds of delayed puberty
Pre-pubertal alcohol and tobacco use disrupts endocrine system and alters the timing of pubertal development (breast development)
amenorrhea
irregular menses
Family Dynamics (Socio-Behavioral Factors in pubertal maturation)
Girls from father-absent, less-cohesive and conflicted homes - Menstruate at an earlier age (vs girls from mother-absent, intact, cohesive homes)
Girls who experience father absence matured 4-5 months earlier
Puberty increases conflict, diminishes closeness
But distance, in turn, accelerates pubertal maturation
Later adrenarche predicted by (study where Family environments assess when kids in preschool,
Adrenal hormones assayed when kids are age 7,
Secondary sexual characteristics reported at age 11)
High quality of “paternal investment” - fathers spend time with kids
Less marital conflict
High maternal supportiveness
Lower 3rd-grade BMI
Greater maternal harshness at 54 months predicted
early age of menarche
Infant attachment insecurity at 15 months predicts
early pubertal maturation
Girls who had been insecure infants
Completed pubertal development earlier & earlier age of menarche
Girls growing up under family stress (conflict, marital discord, instability) experience ___ causing ___ that provokes earlier pubertal onset
experience behavioral/psychological problems
e.g., internalizing symptoms (depression, anxiety)
That lowers metabolism, leading to weight gain
provokes earlier pubertal onset and “reproductive readiness”
Four Points on do Hormones Rage
- Effect of T on behavior is indirect/provoked
- Effect of adrenal hormones is moderated by other social-behavioral factors
- Hormones and moodiness? Not so much
- Prenatal hormones may be decisive
Direct & indirect effects of T
Provoked v Unprovoked Aggression
Direct - Provoked - T exerts direct causal pathway to provoked aggression
Indirect - Unprovoked - Indirect causal path to unprovoked aggression (by lowering boys’ tolerance for frustration )
Andrenal hormone levels
Low DHEAS - More aggressive behavior - In girls who experience many negative life events
High DHEAS - More emotional distress- IN early maturing girls
High adrenal androgens- More behavioral problems- In girls whose adrenarche is early
Hormones and Moodiness
direct connection is not very strong
When there is a connection…
Strongest effects “early” when “switched on”
When hormone levels fluctuate
Rapid increase may be associated with irritability, impulsivity, aggression (boys) depression (girls)
____ play a far greater role in development of depression/negative mood than do hormonal changes
Stressful life events
Effects of T on aggression & impulsivity are ____ among teens with positive family relationships or strong self-control
weaker
Shifts in mood have more to do with ____ than with internal biological activities
shifts in activities
Before 8 weeks the brain is ___ untill exposed to ___
Before 8 weeks the brain is “feminine” until exposed to “masculinizing” hormones like T
___ program” the brain to develop in certain ways
Presence or absence of certain hormones in early life
prenatal development hormones organize the brain in ways that may not be evident until later
sex differences in aggression may not appear until __
but are a result from __ rather then ___
adolescence,
But they likely result from impact of prenatal hormones rather than hormonal changes at puberty
It is possible for an early-maturing & fast-maturing youngster to complete pubertal maturation by age ___
___ years before a later-maturing youngster even begun puberty
___ years before a late-maturing and slow-maturing youngster has matured completely
10
3 years before a later-maturing youngster even begun puberty
8 years before a late-maturing and slow-maturing youngster has matured completely
relation between age at which puberty begins and rate at which pubertal development proceeds
No relation between
Late maturers vs early on hight
Late maturers vs early on weight
Late maturers on average become taller than early maturers as adults;
and early-maturers heavier (at least among girls)
Ethnic differences in timing/rate in US
Black girls mature earlier than Mexican American girls—who mature earlier than White Girls
Reasons not known, but does not appear to be due to ethnic differences in income, weight or area of residence (but maybe to differential exposure to chemicals, e.g., hair care products)
Early Maturation in Boys
Early maturation has many advantages
But there are some risks, too
Impact of victimization is greater for early maturers
More likely to engage in minor delinquencies, use drugs or alcohol, misbehave in school
why:
- Less supervised by adults
- Hang-out in contexts conducive to delinquencies
- Have older friends
Selection & Socialization - select group (older, more similar) they then socialize you to these things
Early Maturation in girls
Early maturation is harder on girls
More emotional difficulties
Poorer self-image
Higher rates of depression, eating disorders, panic attacks
Negative effects more pronounced for____ early maturing girls
white
(vs. Black or Hispanic peers)
Adverse effects of early puberty for boys & girls limited to teens who __
came from high-risk households
Puberty not inherently stressful, but exacerbates other stressors, e.g., transition to middle school
Are early-maturing girls less popular?
Not necessarily
- Are more popular than other girls when index of popularity includes popularity with boys
- Socially skilled early maturing girls have less difficulty
- Are popular with boys but also frequent victims of rumor & gossip
- More likely to suffer from social anxiety (pressure to date, sex)
Early-maturing girls are more vulnerable to emotional distress when they have __
relatively more friends with boys
Or attend school with older peers
Four Theoretical Perspectives on Puberty and Adaptation
- Maturational deviance hypothesis
- Developmental readiness
- Individual diathesis-stress model
- Contextual amplification
secular trend
decline in age in menarche over time
Maturational deviance
Youngsters who stand out or are “off-time” experience more “transition stress”
Early maturing girls “deviate socially” for a limited time
They resemble chronologically older groups of teens and their behavior does not deviate from them
At age 15 early maturing girls were more likely to:
Have been truant, caught cheating, tried marijuana
6xs more likely to have reported multiple episodes of drunkenness
Link between age at menarche and “norm violations mediated by peer affiliation” (had older friends)
But problems did not persist into adulthood
But early-maturing girls, as adults:
entered “pair relations” earlier, married earlier, had children earlier, entered work force earlier
Developmental Readiness
Missed opportunities for age-appropriate socialization (harder on girls)
Contextual Amplification
Experiencing pubertal transition in deviant contexts increases probability of behavior problems/emotional distress
Individual Diathesis-Stress
Vulnerabilities prior to adolescence accentuate problems of transition stress
