11

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

22

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

33

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

44

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)

55

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

66

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

77

•• 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

88

99

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