1. Hormones & Sexual Development
Lesson 21

2. Let’s Talk About Sex It’s complicated
Cognitive, behavioral, emotional, cultural factors
Chromosomal sex
Genotype vs. phenotype
Sex vs Gender
Sex: biological
Gender: self-perception ~

3. Gender Based on individual’s own perceptions
Can be independent of phenotype
Sexual Identity
Individual’s perception of own phenotype
Sexual orientation
Based on focus of sexual attraction ~

4. Olympics & Sex Caster Semenya Olympic gold medalist Male or female?
Ambiguous genitalia
No ovaries or uterus
Hi testosterone levels
Disqualify her? ~

5. Sexual Dimorphism Two forms male and female
What determines your sex? ~

6. Genetic determinants XX or XY XO ? Turner’s syndrome no ovaries
default = FEMALE
MALE
Override genetic program ~

7. Genotypic vs Phenotypic Sex
Genotype
complete genetic makeup
Phenotype
expression of genes ~

8. Sexual Differentiation of Body
Chromosomal sex - XX or XY
single gene
Sex-Determining Region (or sex reversal) on the Y Chromosome
SRY ~

9. SRY Turns on switch testes development XX + SRY? male XY - SRY
female ~

10. Development of Reproductive Organs

11. Primordial Gonad Indifferent gonad Potential for both sexes Medulla
testes
Cortex
ovaries ~

12. Differentiation at 6 weeks SRY medulla  testes No SRY
cortex  ovaries ~

13. Internal Reproductive Ducts
< 6 weeks
2 sets
Müllerian system = female
upper vagina
uterus
fallopian tubes ~

14. Internal Reproductive Ducts
Wolffian system = male
seminal vesicles
vas deferens
3d month development
1 set withers
SRY  testes
testosterone
Müllerian Inhibiting Hormone - MIH ~

15. Müllerian Inhibiting Hormone
Testes  scrotum develops
Mullerian degenerates
Testosterone stimulates wolffian
Testosterone to female
get both systems
No MIH
Critical periods
No MIH  Mullerian ~

16. External Genitalia Dihydrotestosterone (DHT) critical period
5 - -reductase
M & F - same tissue ~

17. Sexual Differentiation of the Brain

18. Masculinization Gonadotropin release patterns Female natural pattern
Brain masculinized by...
testosterone?
NO!ESTRADIOL
Structural differences? ~

19. Sexual Dimorphism of the Brain
Hypothalamus
Sexually Dimorphic Nucleus - SDN
Spinal Nucleus of the Bulbocavernosus ~

20. Masculinization of the Brain
testosterone > estradiol
aromatase
Aromatase present in neonates
inject estradiol into neonate female
brain masculinized
What protects females?
Rats - -fetoprotein
Primates - placenta? ~

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

22. Sexual Development Syndromes

23. Adrenogenital Syndrome
Congenital adrenal hyperplasia
genotype: XX
prenatal adrenal cortex hyperactivity
high levels of androgens
partially masculinized external genitalia ~

24. Androgen Insensitivity Syndrome
Sex?
Phenotype?
Genotype?

25. Androgen Insensitivity Syndrome
Genotype: XY
No androgen receptors
Genetic mutation - X chromosome gene
Born with vagina, raised as female
Undescended testes become functional at puberty.
NOW WHAT HAPPENS?
Female body, brain, & gender identity

26. 5-alpha Reductase Syndrome
Genetically XY
Fetal 5-alpha reductase deficiency
T not converted to DHT
Born with female external genitalia
maybe raised as female
Dominican Republic
1:90 male births ~

27. At puberty Testes become functional & descend at puberty
 testosterone
5-a-reductase present
converts T  DHT
Development of male genitalia
including penis
secondary sex characteristics ~