1. Hormonal Influences
on Sex & Sexuality

2. Hormones, Sex, & Gender Dr. discovers young married woman is male!
Adolescent girl grows penis!
Baby boy undergoes sex change!

3. Hormones Chemical messengers Organizational development
critical periods
Activational
control behavior & physiological processes ~

4. Sex Hormones Steroids derived from cholesterol Estrogens estradiol
Androgens
testosterone
dihydrotestosterone (DHT) ~

5. Dihydro-
testosterone
5- a- reductase
Testosterone
aromatase
Estradiol

6. Sexual Differentiation
Sexually dimorphic
Genotypic sex
sex genes
Phenotypic sex
expression of genes ~

7. Sexual Differentiation
Single gene
Sex-Determining Region on the Y Chromosome
SRY
Testis Determining Factor (TDF) ~

8. Development of Reproductive Organs

9. Primordial Gonad Indifferent gonad first 6 weeks No TDF --> ovaries
cortex
TDF --> testes
medulla ~

10. Internal Reproductive Ducts
Mullerian system
female
Wolffian system
male ~

11. Internal Reproductive Ducts
3d month
1 set withers
TDF ---> testes
testosterone
Mullerian Inhibiting Hormone - MIH ~

12. External Genitalia
Dihydrotestosterone
M/F same primordial tissue ~

13. Sexual Differentiation of the Brain

14. Sexual Differentiation of the Brain
Rats
Hypothalamus
Sexually Dimorphic Nucleus (SDN)
Spinal Cord
Spinal Nucleus of the Bulbocavernosus (SNB) ~

15. NO!--->ESTRADIOL ~ Masculinization Gonadotropin release patterns
Female: cyclical
Male: steady
Brain masculinized by...
testosterone?
NO!--->ESTRADIOL ~

16. Sexually Dimorphic Nucleus
male female androgenized
female

17. Spinal Nucleus of the Bulbocavernosus
F + A M
M - A

18. Secondary sex characteristics
Puberty
Increased M/F sex hormone activity
Secondary characteristics
maturation of genitals
breasts
body shape
Pubic & axillary hair
females- androstenedione ~

19. Sexual Development Syndromes

20. Congenital Adrenal Hyperplasia
Prenatal adrenal cortex hyperactivity
high levels of androgens
partially masculinized external genitalia ~

21. Congenital Adrenal Hyperplasia

22. Androgen Insensitivity Syndrome
Genetically XY -
No androgen receptors
Genetic mutation - X chromosome
Female body, brain, & gender identity
functional testes ~

23. 5- a - Reductase Syndrome
Genetically XY
Fetal 5 - a - reductase deficiency
no dihydrotestosterone
genitalia not masculinized ~

24. At puberty Undescended testes functional Functioning penis develops
Normal male development ~

25. Hormones & Sexual Behavior

26. Sexual Behavior: Rats Controlled by sex hormones Female Proceptive
ear wiggling, darting, hopping
Receptive - lordosis
Male
mounts
copulates ~

27. Organizational Effects of Hormones
SDN & SNB
Critical periods
Humans - prenatal
Rats - Perinatal
easily manipulated ~

28. Hormones: Sexual Behavior
Gonadectomy
at birth
Adult males
testosterone ---> no male behavior
estrogen ---> lordosis
Adult females
estrogens ---> no female behavior
testosterone ---> male behavior ~

29. 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 ~

30. Homosexuality Sex hormones role? rats - yes Humans?
no difference in circulating hormones
Learning experiences?
or biologically determined?

31. Homosexuality Simon LeVay Brains of male AIDS victims
Anterior Hypothalamus
Anterior Commissure
SDN (rats)
Humans: 3rd interstitial nucleus of the Anterior Hypothalamus
INAH-3 ~

32. INAH-3
Male
Female
SDN

33. INAH-3

34. INAH-3
Anterior Commissure similar relationship

35. Suprachiasmatic Nucleus
Swaab & Hoffman (1990)

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

37. 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 ~

38. 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 ~

39. 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 ~