1. Prenatal Sexual Development

2. Why would psychologists be concerned with physical development, especially prenatally?

3. 1. Sex is a powerful determinant and predictor of behavior
2. Prenatal events determine physical sex and influence psychosexual behavior

4. Sex Hormones: Misconceptions
Females have only “female” hormones called estrogens.
Males have only “male” hormones called androgens.

5. Most sex hormones are produced by both males and females…
Just in different quantities

6. “Female” hormones
Estradiol (an estrogen)
Progesterone

7. “Male” hormones Androgens: testosterone dihydrotestosterone (DHT)
androstenedione

8. “Male” hormones Anti-Mullerian Hormone (AMH)
Mullerian Inhibiting Hormone (MIH)
Mullerian Inhibiting Substance (MIS)
AMH is found only in males

9. Differentiating Body Parts
Prenatal Development
Differentiating Body Parts
Gonads (testes & ovaries)
Internal sex organs
External sex organs

10. The Eve Principle
Without the prenatal influence of sex hormones, a fetus will develop as a female regardless of its chromosomes

11. In the beginning . . .
XX chromosomes
XY chromosomes

12. Gonads: Testes and Ovaries
Primordial gonads
Not differentiated into male or female

13. Gonads: Testes and Ovaries
SRY gene on the Y chromosome directs the primordial gonads to make Sry protein

14. Gonads: Testes and Ovaries
Sry protein
aka Testes Determining Factor
aka HY antigen
testes

16. XX chromosomes create ovaries
XY chromosomes create testes
testosterone
Mullerian Inhibiting Hormone (MIH)

17. Internal Sex Organs: e.g., seminal vesicles (male) and uterus (female)
Two precursor systems are present in all fetuses

18. male female Internal sex organs The Mullerian System
Needs no hormones to develop
If MIH, it degenerates
The Wolffian System
Testosterone to develop
or else it degenerates

19. female
male

20. Precursor potentially male or female, like the Primordial Gonads
External Sex Organs:
~ 2-3 months gestational age
Precursor potentially male or female, like the Primordial Gonads

21. male female External sex organs
Masculinized by DHT (dihydro-testosterone)
not testosterone per se
No hormones needed to develop

22. male
female

23. Differentiating the Brain
Prenatal Development
Differentiating the Brain
Hypothalamus

25. No hormones leads to:
Female brain that releases hormones in monthly cycles (after puberty)
Perhaps influences sexual preference

26. With Hormones
Male brain that releases hormones steadily (after puberty)
Probably influences male behaviors (e.g., aggression)
Perhaps influences sexual preference

27. No SRY gene

28. SRY gene T?

29. Strange but predictable anomalies…

30. What would happen if an XY fetus had no receptors for androgens (MIH worked fine)? Androgen Insensitivity Disorder May be partial or full insensitivity Genetically male, female external genitalia, but no internal sex organs (i.e., no menstruation, infertile), little body hair; likely to identify as female.

31. What would happen if an XX fetus was exposed to androgens after the internal sex organs had developed? Female internal reproductive system, masculinized external genitalia.

32. Prader scores in 46XX disorders of sexual development
Prader scores in 46XX disorders of sexual development. Early feminizing genitoplasty is standard of care for Prader score > 3.