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Hormonal Influences. on Sex & Sexuality. Hormones, Sex, & Gender. Dr. discovers young married woman is male! Adolescent girl grows penis! Baby boy undergoes sex change!. Hormones. Chemical messengers Organizational development critical periods Activational

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hormonal influences

Hormonal Influences

on Sex & Sexuality

hormones sex gender
Hormones, Sex, & Gender
  • Dr. discovers young married woman is male!
  • Adolescent girl grows penis!
  • Baby boy undergoes sex change!
hormones
Hormones
  • Chemical messengers
  • Organizational
    • development
    • critical periods
  • Activational
    • control behavior & physiological processes ~
sex hormones
Sex Hormones
  • Steroids
    • derived from cholesterol
  • Estrogens
    • estradiol
  • Androgens
    • testosterone
    • dihydrotestosterone (DHT) ~
slide5
Dihydro-

testosterone

5- a- reductase

Testosterone

aromatase

Estradiol

sexual differentiation
Sexual Differentiation
  • Sexually dimorphic
  • Genotypic sex
    • sex genes
  • Phenotypic sex
    • expression of genes ~
sexual differentiation1
Sexual Differentiation
  • Single gene
  • Sex-Determining Region on the Y Chromosome
    • SRY
  • Testis Determining Factor (TDF) ~
primordial gonad
Primordial Gonad
  • Indifferent gonad
    • first 6 weeks
  • No TDF --> ovaries
    • cortex
  • TDF --> testes
    • medulla ~
internal reproductive ducts
Internal Reproductive Ducts
  • Mullerian system
    • female
  • Wolffian system
    • male ~
internal reproductive ducts1
Internal Reproductive Ducts
  • 3d month
    • 1 set withers
  • TDF ---> testes
    • testosterone
    • Mullerian Inhibiting Hormone - MIH ~
slide12
External Genitalia
  • Dihydrotestosterone
  • M/F same primordial tissue ~
sexual differentiation of the brain1
Sexual Differentiation of the Brain
  • Rats
  • Hypothalamus
    • Sexually Dimorphic Nucleus (SDN)
  • Spinal Cord
    • Spinal Nucleus of the Bulbocavernosus (SNB) ~
masculinization
Masculinization
  • Gonadotropin release patterns
    • Female: cyclical
    • Male: steady
  • Brain masculinized by...
    • testosterone?

NO!--->ESTRADIOL ~

sexually dimorphic nucleus
Sexually Dimorphic Nucleus

male female androgenized

female

secondary sex characteristics
Secondary sex characteristics
  • Puberty
    • Increased M/F sex hormone activity
  • Secondary characteristics
    • maturation of genitals
    • breasts
    • body shape
  • Pubic & axillary hair
    • females- androstenedione ~
congenital adrenal hyperplasia
Congenital Adrenal Hyperplasia
  • Prenatal adrenal cortex hyperactivity
    • high levels of androgens
    • partially masculinized external genitalia ~
androgen insensitivity syndrome
Androgen Insensitivity Syndrome
  • Genetically XY -
    • No androgen receptors
    • Genetic mutation - X chromosome
  • Female body, brain, & gender identity
    • functional testes ~
5 a reductase syndrome
5- a - Reductase Syndrome
  • Genetically XY
  • Fetal 5 - a - reductase deficiency
    • no dihydrotestosterone
    • genitalia not masculinized ~
at puberty
At puberty
  • Undescended testes functional
    • Functioning penis develops
    • Normal male development ~
sexual behavior rats
Sexual Behavior: Rats
  • Controlled by sex hormones
  • Female
    • Proceptive
      • ear wiggling, darting, hopping
    • Receptive - lordosis
  • Male
    • mounts
    • copulates ~
organizational effects of hormones
Organizational Effects of Hormones
  • SDN & SNB
  • Critical periods
    • Humans - prenatal
    • Rats - Perinatal
      • easily manipulated ~
hormones sexual behavior1
Hormones: Sexual Behavior
  • Gonadectomy
    • at birth
  • Adult males
    • testosterone ---> no male behavior
    • estrogen ---> lordosis
  • Adult females
    • estrogens ---> no female behavior
    • testosterone ---> male behavior ~
human sexual behavior
Human Sexual Behavior
  • No stereotypical M & F behaviors
  • Men are like rats
    • Testosterone: activational role
  • Women
    • Estrogens no activational effects
    • Testosterone levels correlated with frequency of intercourse ~
homosexuality
Homosexuality
  • Sex hormones role?
    • rats - yes
    • Humans?
      • no difference in circulating hormones
  • Learning experiences?
  • or biologically determined?
homosexuality1
Homosexuality
  • Simon LeVay
    • Brains of male AIDS victims
    • Anterior Hypothalamus
    • Anterior Commissure
  • SDN (rats)
    • Humans: 3rd interstitial nucleus of the Anterior Hypothalamus
    • INAH-3 ~
inah 3
INAH-3

Male

Female

SDN

inah 32
INAH-3
  • Anterior Commissure similar relationship
suprachiasmatic nucleus
Suprachiasmatic Nucleus

Swaab & Hoffman (1990)

homosexuality 2 hypotheses
Homosexuality: 2 Hypotheses
  • 1. Androgen levels
    • low in XY fetuses that---> gay
    • high in XX fetuses ---> lesbian ~
homosexuality 2 hypotheses1
Homosexuality 2 Hypotheses

2. Inherited Genes

  • MZ twin concordance approx. 50%
    • DZ twins approx. 20%
  • Xq28- tip of the X chromosome
    • 33 of 40 pairs of gay brothers
    • fetal brain response to androgens ~
nature vs nurture
Nature vs. Nurture
  • John/Joan
    • penis destroyed during circumcision
  • 1960s - Gender deemed neutral at birth
    • constructed female genitalia
    • hormone treatment
    • 12 yrs old: positive results reported ~
nature vs nurture1
Nature vs. Nurture
  • By 14 yrs old: living as male
    • reconstructive surgery
    • male hormone treatment
    • married by 25
  • Reassessment in 1996
    • rejected female role much earlier
  • Pendulum swings back toward nature
    • sex/gender not so malleable ~
ad