Hormones & Sexual Development

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 testosterone ------------------------> DHT 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 ~