Download ESTRADIOL

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
 control behavior & physiological
processes ~

Sex Hormones
Steroids
 derived from cholesterol
 Estrogens
 estradiol
 Androgens
 testosterone
 dihydrotestosterone (DHT) ~

5- a- reductase
Dihydrotestosterone
aromatase
Estradiol
Testosterone
Sexual Differentiation
Sexually dimorphic
 Genotypic sex
 sex genes
 Phenotypic sex
 expression of genes ~

Sexual Differentiation
Single gene
 Sex-Determining Region on the Y


Chromosome
 SRY
Testis Determining Factor (TDF) ~
Development of
Reproductive Organs
Primordial Gonad
Indifferent gonad
 first 6 weeks
 No TDF --> ovaries
 cortex
 TDF --> testes
 medulla ~

Internal Reproductive Ducts
Mullerian system
 female
 Wolffian system


male ~
Internal Reproductive Ducts
3d month
 1 set withers
 TDF ---> testes
 testosterone
 Mullerian
Inhibiting
Hormone - MIH ~

External Genitalia
Dihydrotestosterone
 M/F same primordial
tissue ~

Sexual Differentiation
of the Brain
Sexual Differentiation
of the Brain
Rats
 Hypothalamus
 Sexually Dimorphic
Nucleus (SDN)
 Spinal Cord
 Spinal Nucleus of the
Bulbocavernosus
(SNB) ~

Masculinization
Gonadotropin release patterns
 Female: cyclical
 Male: steady
 Brain masculinized by...
 testosterone?

NO!--->ESTRADIOL ~
Sexually Dimorphic Nucleus
male
female
androgenized
female
Spinal Nucleus of the Bulbocavernosus
M
F
M-A
F+A
Secondary sex characteristics
Puberty
 Increased M/F sex hormone activity
 Secondary characteristics
 maturation of genitals
 breasts
 body shape
 Pubic & axillary hair
 females- androstenedione ~

Sexual Development
Syndromes
Congenital Adrenal Hyperplasia

Prenatal adrenal cortex hyperactivity
 high levels of androgens
 partially masculinized external
genitalia ~
Congenital
Adrenal
Hyperplasia
Androgen Insensitivity Syndrome
Genetically XY  No androgen
receptors
 Genetic mutation X chromosome
 Female body, brain, &
gender identity
 functional testes ~

5- a - Reductase Syndrome
Genetically XY
 Fetal 5 - a - reductase
deficiency
 no dihydrotestosterone
 genitalia not
masculinized ~

At puberty

Undescended testes functional
 Functioning penis develops
 Normal male development ~
Hormones &
Sexual Behavior
Sexual Behavior: Rats
Controlled by sex hormones
 Female
 Proceptive

ear wiggling, darting, hopping
Receptive - lordosis
 Male
 mounts
 copulates ~

Organizational Effects of Hormones
SDN & SNB
 Critical periods
 Humans - prenatal
 Rats - Perinatal

easily manipulated ~
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
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

Sex hormones role?
 rats - yes
 Humans?
no difference in circulating hormones
Learning experiences?
 or biologically determined?

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
Male
SDN
Female
INAH-3
INAH-3

Anterior Commissure similar relationship
Suprachiasmatic Nucleus
Swaab & Hoffman (1990)
Homosexuality: 2 Hypotheses

1. Androgen levels
 low in XY fetuses that---> gay
 high in XX fetuses ---> lesbian ~
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
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. 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 ~
