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Lecture 6: Puberty & Puberty RitualsLecture 6: Puberty & Puberty Rituals
•• MenarcheMenarche
•• What causes menarche?What causes menarche?
>> 1. Frisch 1. Frisch ““FatnessFatness””hypothesis hypothesis
>> 2. Tanner/Ellison 2. Tanner/Ellison ““Pelvic Pelvic SizeSize””
•• Hormonal Changes with Hormonal Changes with menarchemenarche
•• Sex differences in timing Sex differences in timing of pubertyof puberty
•• Puberty RitualsPuberty Rituals
Behavioral Biology of Women — 2007
MenarcheMenarche
What Triggers Menarche?What Triggers Menarche?
•• Frisch Frisch ““Body FatBody Fat””
HypothesisHypothesis
•• Tanner/Ellison: Tanner/Ellison: ““Pelvic Pelvic
SizeSize”” HypothesisHypothesis
Frisch Frisch ““Body FatBody Fat”” HypothesisHypothesis
•• Accumulation of Accumulation of weight or fat is critical weight or fat is critical for menarchefor menarche
Frisch Hypothesis Frisch Hypothesis -- Version 1Version 1
•• Average weight at Average weight at menarche is 47 kgmenarche is 47 kg
•• Thus, 47 kg isThus, 47 kg is a critical a critical weight that triggers weight that triggers menarchemenarche
(Frisch & Revelle, 1970)
•• PROBLEM: Graph PROBLEM: Graph shows there isshows there is NO NO relationship!relationship!
Frisch Hypothesis Frisch Hypothesis -- VersionVersion 22
•• Looked at weight for Looked at weight for height insteadheight instead
(Frisch, Revelle & Cook 1970)
•• Found critical body Found critical body composition that composition that triggers menarchetriggers menarche
•• PROBLEM: assumes PROBLEM: assumes Difference in body Difference in body composition is due to composition is due to FATFAT
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Frisch Hypothesis Frisch Hypothesis -- VersionVersion 33
•• Few girls reached Few girls reached menarche below 17% menarche below 17% body weight as fatbody weight as fat
(Frisch & McArthur 1974)
•• Said this was a Said this was a minimum threshold for minimum threshold for menarchemenarche
•• PROBLEM: No PROBLEM: No evidence of increase in evidence of increase in probability of reaching probability of reaching menarche after attain menarche after attain 17% body fat17% body fat
Pelvic Size HypothesisPelvic Size Hypothesis
•• A girl must reach an appropriate age of A girl must reach an appropriate age of
skeletal development in order to reproduceskeletal development in order to reproduce
Pelvic Size HypothesisPelvic Size Hypothesis
•• A girl must reach an appropriate A girl must reach an appropriate age of skeletal development in age of skeletal development in order to reproduceorder to reproduce
•• Pelvic dimensions are Pelvic dimensions are significantly correlated with significantly correlated with menstrual agemenstrual age
Pelvic Size HypothesisPelvic Size Hypothesis
•• A girl must reach an A girl must reach an appropriate age of skeletal appropriate age of skeletal development in order to development in order to reproducereproduce
•• Pelvic dimensions are Pelvic dimensions are significantly correlated with significantly correlated with menstrual agemenstrual age
•• A biA bi--iliac diameter (pelvic iliac diameter (pelvic breadth) of 24 centimeters breadth) of 24 centimeters seems to be a minimum seems to be a minimum thresholdthreshold
Comparison of HypothesesComparison of Hypotheses
•• Ellison studied data from 67 girls weighed Ellison studied data from 67 girls weighed
and measured twice a year from 8 to 18 yrs.and measured twice a year from 8 to 18 yrs.
Graph of Menarcheal age and Wt.Graph of Menarcheal age and Wt.
Ellison
•• Weight accounts for 18% of the variance inWeight accounts for 18% of the variance in
menarcheal menarcheal ageage
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Skeletal Growth and Age at MenarcheSkeletal Growth and Age at Menarche
Ellison•• Height accounts for 50% of the varianceHeight accounts for 50% of the variance Ellison
Comparison of HypothesesComparison of Hypotheses
•• CONCLUSION: Menarche occurs after CONCLUSION: Menarche occurs after
peak growth spurtpeak growth spurt
Comparison of HypothesesComparison of Hypotheses
•• Weight accounts for 18% of the variance inWeight accounts for 18% of the variance in
menarcheal menarcheal ageage
•• Height accounts for 50% of the varianceHeight accounts for 50% of the variance
•• Natural selection has delayed menarche Natural selection has delayed menarche
until pelvis can handle reproduction without until pelvis can handle reproduction without
complicationscomplications
•• Menarche occurs after peak growth spurtMenarche occurs after peak growth spurt
Why theWhy the Confusion?Confusion?
•• Fat IS important for female reproductionFat IS important for female reproduction
Why theWhy the Confusion?Confusion?
•• Fat IS important for female reproductionFat IS important for female reproduction
•• But, attaining an adequate SIZE comes firstBut, attaining an adequate SIZE comes first
Why theWhy the Confusion?Confusion?
•• Fat IS important for female reproductionFat IS important for female reproduction
•• But, attaining an adequate SIZE comes firstBut, attaining an adequate SIZE comes first
•• Attaining adequate ENERGY for Attaining adequate ENERGY for
reproduction comes nextreproduction comes next
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Hormonal and Hormonal and
Developmental ChangesDevelopmental Changes
AndrogensAndrogens
•• About age 8 adolescent growth spurt begins About age 8 adolescent growth spurt begins
through action of androgens and growth through action of androgens and growth
hormones. Originates in adrenal gland.hormones. Originates in adrenal gland.
AndrogensAndrogens
•• About age 8 adolescent growth spurt begins About age 8 adolescent growth spurt begins
through action of androgens and growth through action of androgens and growth
hormones. Originates in adrenal gland.hormones. Originates in adrenal gland.
•• Androgens from adrenal gland and ovary Androgens from adrenal gland and ovary
stimulate pubic andstimulate pubic and axillary axillary hair hair
developmentdevelopment
Estradiol Estradiol -- II
•• Increase in Increase in estradiol estradiol ~8~8--9 yrs starts development of 9 yrs starts development of
breasts, uterus, vagina, parts of pelvisbreasts, uterus, vagina, parts of pelvis
•• Pelvic remodelingPelvic remodeling finishesfinishes at the end of skeletal at the end of skeletal
maturationmaturation
Breast DevelopmentBreast Development Breast DevelopmentBreast Development
•• BreastBreast
developmentdevelopment
occurs firstoccurs first
•• Influence of Influence of
estradiol estradiol and and
prolactinprolactin (from (from
anterior pituitary)anterior pituitary)
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Estradiol Estradiol -- IIII
•• Eventually stimulates mineral deposition Eventually stimulates mineral deposition
resulting in ossification and fusion of resulting in ossification and fusion of
epiphysesepiphyses
Precocious PubertyPrecocious Puberty
•• Treatable Treatable
with estrogen with estrogen
antagonistantagonist
Delayed or Loss of PubertyDelayed or Loss of Puberty
•• Treatable Treatable
with with GnRHGnRH
Skeletal Development Skeletal Development -- OverallOverall
•• Androgens Androgens (testosterone)(testosterone)
•• Growth Hormone from anterior pituitaryGrowth Hormone from anterior pituitary
•• EstradiolEstradiol
Pubertal DevelopmentPubertal Development HYPOTHALAMUS
ANTERIOR PITUITARY
OVARY
Follicle
FSH LH
Estrogens
GnRH
Negative Feedback
•• During 3rd month in During 3rd month in utero utero negative feedback startsnegative feedback starts
•• As system matures more estrogen needed to turn system offAs system matures more estrogen needed to turn system off
•• Finally enough FSHFinally enough FSH released to stimulate follicle to developreleased to stimulate follicle to develop
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HYPOTHALAMUS
ANTERIOR PITUITARY
OVARY
Follicle
FSH LH
Estrogens
GnRH
Negative Feedback
Positive Feedback
•• Positive feedback starts in response to high estrogenPositive feedback starts in response to high estrogen
•• Capacity to evoke LH Surge occurs late in pubertal processCapacity to evoke LH Surge occurs late in pubertal process
Gonadal Gonadal Maturation: 3 HypothesesMaturation: 3 Hypotheses
•• Gonadostat Gonadostat
HypothesisHypothesis
•• Falling sensitivity Falling sensitivity
of hypothalamus to of hypothalamus to
negative feedback negative feedback
of steroidsof steroids
Gonadal Gonadal Maturation: 3 HypothesesMaturation: 3 Hypotheses
•• Pituitary Drive Pituitary Drive
HypothesisHypothesis
•• Pituitary produces Pituitary produces
increasing FSH and increasing FSH and
LH (LH (gonadotropinsgonadotropins) )
in response to the in response to the
same same GnRH GnRH
stimulus from stimulus from
hypothalamushypothalamus
Gonadal Gonadal Maturation: 3 HypothesesMaturation: 3 Hypotheses
•• Gonadal Gonadal Drive Drive
HypothesisHypothesis
•• Changes in gonad Changes in gonad
come firstcome first
•• Increasing amounts Increasing amounts
of steroid cause of steroid cause
hypothalamus to hypothalamus to
lose sensitivity to lose sensitivity to
negative feedbacknegative feedback
Development of LH pulsesDevelopment of LH pulses
•• PrePre--puberty: No puberty: No
LH PulsesLH Pulses
•• Early Puberty: Early Puberty: Production Production
of LH pulses begins, of LH pulses begins,
especially at nightespecially at night
•• Late Puberty: Late Puberty: Increasing Increasing
magnitude and frequency magnitude and frequency
of pulses, also during dayof pulses, also during day
AdolescentAdolescent SubfecunditySubfecundity
•• Between 55%Between 55%--85% menstrual cycles during 85% menstrual cycles during
first 2 years are anovulatoryfirst 2 years are anovulatory
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•• HOWEVER, Any individual cycle may beHOWEVER, Any individual cycle may be ovulatoryovulatory!!
Secular TrendSecular Trend
Differences between males and femalesDifferences between males and females PubertyPuberty
Stages of PubertyStages of Puberty
•• Breast DevelopmentBreast Development
•• Pubic HairPubic Hair
•• Growth SpurtGrowth Spurt
•• Hip broadeningHip broadening
•• MenstruationMenstruation
•• Fat DepositionFat Deposition
•• Fully Fully ““fecundfecund”” cyclescycles
•• Testes enlargement & Testes enlargement & sperm productionsperm production
•• Pubic hairPubic hair
•• Penis enlargementPenis enlargement
•• Growth spurtGrowth spurt
•• Axillary hairAxillary hair
•• Facial hairFacial hair
•• Voice changesVoice changes
•• Broadening of shoulders Broadening of shoulders ““filling outfilling out””
FemalesFemales MalesMales
Puberty RitualsPuberty Rituals
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Mondari of Sudan
Krobo and Shai of Ghana Krobo and Shai of Ghana
Pokot Girls Surma
1010
Surma Mbuti
Western Puberty Rituals?Western Puberty Rituals? Puberty RitualsPuberty Rituals
•• Signs of menarche Signs of menarche
•• ScarificationScarification
•• AdornmentAdornment
•• Hair style changesHair style changes
•• Restricted access to menRestricted access to men
•• SeclusionSeclusion
•• Symbolic clothingSymbolic clothing
Next Time...Next Time...
•• Menstruation Menstruation —— why did it why did it
evolve?evolve?
•• Menstrual seclusion huts and Menstrual seclusion huts and
menstrual taboosmenstrual taboos
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