Hormones & Sexual Development Lesson 21

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 ~

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 ~

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

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 complete genetic makeup Phenotype expression of genes ~

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

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

Development of Reproductive Organs

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

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

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

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

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

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

Sexual Differentiation of the Brain

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

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

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? ~

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 ~

Sexual Development Syndromes

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

Androgen Insensitivity Syndrome Sex? Phenotype? Genotype?

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

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 ~

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 ~