Hormones & Sexual Development

Lecture 25

Sex, & Gender Sex

biological differences male & female intersex

Gender self-identity about sex role may or may not match sex heterosexual, homosexual,

trans-gendered ~

Hormones

Chemical messengers Organizational

development critical (sensitive) periods permanent changes

Activational control behavior & physiological

processes temporary ~

Sex Hormones

Steroids derived from cholesterol

Estrogens estradiol

Androgens testosterone (T) dihydrotestosterone (DHT) ~

Testosterone

Dihydro-testosterone

Estradiol

5- - reductase

aromatase

Sexual Differentiation

Sexually dimorphic Genotypic sex

sex genes Phenotypic sex

expression of genes ~

Sexual Differentiation

Single gene Sex-Determining Region on the Y

Chromosome SRY

Testis Determining Factor (TDF) ~

Development of Reproductive Organs

Primordial Gonad

Indifferent gonad first 6 weeks

No TDF ovaries cortex

TDF testes medulla ~

Internal Reproductive Ducts

Müllerian system female

Wolffian system male

3d month 1 set withers

TDF testes testosterone Müllerian Inhibiting Hormone - MIH ~

External Genitalia

Dihydrotestosterone

M/F same primordial tissue ~

Sexual Differentiation of the Brain

Rats Hypothalamus

Sexually Dimorphic Nucleus (SDN)

Spinal Cord Spinal Nucleus of the

Bulbocavernosus (SNB) ~

Masculinization of Brain

Gonadotropin release patterns Female: cyclical Male: steady

Brain masculinized by... testosterone?

Aromatase converts T estradiol inside neurons ~

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 glands

~

Sexual Development Syndromes

Congenital Adrenal Hyperplasia

Genotype: XX Prenatal adrenal cortex hyperactivity

high levels of androgens partially masculinized external genitalia ~

Androgen Insensitivity Syndrome

Genotype: XY No androgen

receptors Genetic mutation - X

chromosome Female body, brain, &

gender identity functional testes ~

5- - Reductase Syndrome

Genotype: XY Fetal 5 - - reductase

deficiency no dihydrotestosterone genitalia not masculinized

Rare except Dominican

Republic 1:90 ~

At puberty Undescended testes functional

5- -reductase present: T DHT Normal male development

Functioning penis develops ~

What Determines Sex?

Interaction of… genes hormones during critical periods

Sexual differentiation of… body brain ~