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Hormones & Sexual Development

Hormones & Sexual Development. Lecture 23. Sexual Dimorphism. Two forms male and female What determines your sex? ~. Genetic determinants. XX or XY XO ? Turner’s syndrome no ovaries default = FEMALE MALE Override genetic program ~. Genotypic vs Phenotypic Sex. Genotype

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Hormones & Sexual Development

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  1. Hormones & Sexual Development Lecture 23

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

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

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

  5. Sexual Differentiation of Body • Chromosomal sex - XX or XY • single gene • Sex-Determining Region on the Y Chromosome • SRY ~

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

  7. Development of Reproductive Organs

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

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

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

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

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

  13. External Genitalia • Dihydrotestosterone (DHT) • critical period testosterone ------------------------> DHT 5 - -reductase • M & F - same tissue ~

  14. Sexual Differentiation of the Brain

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

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

  17. 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? ~

  18. 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 ~

  19. Sexual Development Syndromes

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

  21. Androgen Insensitivity Syndrome • Sex? • Phenotype? • Genotype?

  22. 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

  23. 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 ~

  24. At puberty • Undescended testes become functional at puberty •  testosterone • 5-a-reductase present • converts T  DHT • Development of male genitalia • including penis • secondary sex characteristics ~

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