Hormones & Sexual Development Lecture 25

Sex, & Gender n Sex l biological differences l male & female l intersex n Gender l self-identity about sex role l may or may not match sex l heterosexual, homosexual, trans-gendered ~

Hormones n Chemical messengers n Organizational l development l critical (sensitive) periods l permanent changes n Activational l control behavior & physiological processes l temporary ~

Sex Hormones n Steroids l derived from cholesterol n Estrogens l estradiol n Androgens l testosterone (T) l dihydrotestosterone (DHT) ~

Testosterone Dihydro- testosterone Estradiol 5-  - reductase aromatase

Sexual Differentiation n Sexually dimorphic n Genotypic sex l sex genes n Phenotypic sex l expression of genes ~

Sexual Differentiation n Single gene n S ex-Determining R egion on the Y Chromosome l SRY n Testis Determining Factor (TDF) ~

Development of Reproductive Organs

Primordial Gonad n Indifferent gonad l first 6 weeks n No TDF  ovaries l cortex n TDF  testes l medulla ~

Internal Reproductive Ducts n Müllerian system l female n Wolffian system l male n 3d month l 1 set withers n TDF  testes l testosterone l Müllerian Inhibiting Hormone - MIH ~

External Genitalia n Dihydrotestosterone n M/F same primordial tissue ~

Sexual Differentiation of the Brain n Rats n Hypothalamus l Sexually Dimorphic Nucleus (SDN) n Spinal Cord l Spinal Nucleus of the Bulbocavernosus (SNB) ~

Masculinization of Brain n Gonadotropin release patterns l Female: cyclical l Male: steady n Brain masculinized by... l testosterone? n Aromatase converts T  estradiol l inside neurons ~

Secondary sex characteristics n Puberty l Increased M/F sex hormone activity n Secondary characteristics l maturation of genitals l breasts l body shape n Pubic & axillary hair l females- androstenedione from adrenal glands ~

Sexual Development Syndromes

Congenital Adrenal Hyperplasia n Genotype: XX n Prenatal adrenal cortex hyperactivity l high levels of androgens l partially masculinized external genitalia ~

Androgen Insensitivity Syndrome n Genotype: XY l No androgen receptors l Genetic mutation - X chromosome n Female body, brain, & gender identity l functional testes ~

5-  - Reductase Syndrome n Genotype: XY Fetal 5 -  - reductase deficiency l no dihydrotestosterone l genitalia not masculinized n Rare l except Dominican Republic l 1:90 ~

At puberty n Undescended testes functional 5-  -reductase present: T  DHT n Normal male development l Functioning penis develops ~

What Determines Sex? n Interaction of… l genes l hormones l during critical periods n Sexual differentiation of… l body l brain ~