Hormones and Sexuality – Part 1

Hormones and Sexuality – Part 1 APSY 214: Unit 3

Admin • No office hours this Friday

Today’s goals • At the end of the today, you should be able to… • Distinguish between the major structures and hormones involved in the regulation of gonadal hormones • Explain the process involved in the regulation of gonadal hormones, starting with the hypothalamus and its hormones • Explain how sexual differentiation occurs for: • Gonads • Internal reproductive ducts • External reproductive organs

Today’s goals • At the end of the today, you should be able to… • Describe the hormonal changes that occur during puberty and the effect they have on the body • Explain the aromatization hypothesis • Summarize what we understand about sexual differentiation in the mammalian brain, including • Aromatization hypothesis and humans • Key findings in the area

Sample test question Sry protein triggers the development of: • the testes. • a Müllerian system. • the penis. • ovaries.

Sample test question The aromatization hypothesis states that: • Testosterone is directly responsible for masculinizing the brain • Male and female brains are not differentiated (i.e. there are no sex difference in brain development) • estradiol created in the brains of developing males from circulating testosterone masculinizes their brains. • estradiol created in the brains of developing females from circulating testosterone feminizes their brains.

The Neuroendocrine System

Regulation of gonadal hormones Hypothalamus Gonadotropin releasing hormone (via veins) Anterior pituitary Gonadotropins Gonads Estrogens, androgens, progestins Body tissue

Goal review • You should now be able to… • Distinguish between the major structures and hormones involved in the regulation of gonadal hormones • Explain the process involved in the regulation of gonadal hormones, starting with the hypothalamus and its hormones

Sexual differentiation

Male or female? How do we become male or female? What role do sex hormones play? ?

Think about it A normal genetic female receives injections of testosterone throughout fetal development. She will be born with: • ovaries. • male internal reproductive ducts. • undeveloped female reproductive ducts. • male external reproductive organs. • all of the above

Think about it A normal genetic female receives injections of testosterone throughout fetal development. She will be born with: • ovaries. • male internal reproductive ducts. • undeveloped female reproductive ducts. • male external reproductive organs. • all of the above 1:00

Think about it A normal genetic female receives injections of testosterone throughout fetal development. She will be born with: • ovaries. • male internal reproductive ducts. • undeveloped female reproductive ducts. • male external reproductive organs. • all of the above :30

4:00 Activity 2 A normal genetic female receives injections of testosterone throughout fetal development. She will be born with: • ovaries. • male internal reproductive ducts. • undeveloped female reproductive ducts. • male external reproductive organs. • all of the above

:30 Activity 2 A normal genetic female receives injections of testosterone throughout fetal development. She will be born with: • ovaries. • male internal reproductive ducts. • undeveloped female reproductive ducts. • male external reproductive organs. • all of the above

Time’s up! Activity 2 A normal genetic female receives injections of testosterone throughout fetal development. She will be born with: • ovaries. • male internal reproductive ducts. • undeveloped female reproductive ducts. • male external reproductive organs. • all of the above

Activity 2 - Answer A normal genetic female receives injections of testosterone throughout fetal development. She will be born with: • ovaries. • male internal reproductive ducts. • undeveloped female reproductive ducts. • male external reproductive organs. • all of the above

Activity 2 - Recap • Let’s walk through typical sexual development • There are three components. Differentiation of the: • Gonads • Testes and ovaries • Internal reproductive ducts • Male – includes vas deferens • Female – inclues uterus, fallopian tubes • External reproductive organs • Male – penis, scrotum • Female – clitoris, labia

Activity 2 - Recap • Gonads • 6 weeks after fertilization • Both sexes • Primordial glands • Males • Sry gene (Y chromosome) -> Sry protein -> primordial gonads -> testes • Females • No Sry gene (no Y chromosome) -> no Sry protein -> primoridal gonads -> ovaries • Add testosterone?

Activity 2 - Recap • Internal Reproductive Ducts • 6 weeks after fertilization • Both sexes – Wolffian and Müllerian systems • Male • Testes -> androgens -> development of Wolffian • Testes -> Müllerian-inhibiting substance -> degeneration of Müllerian system • Female • No testes -> no androgen -> no development of Wolffian • Add testosterone?

Activity 2 - Recap • External reproductive organs • 2nd month of pregnancy • Both sexes – biopotential precursor • Males • Testosterone -> male external genitalia • Females • No testosterone -> female external genitalia • Add testosterone?

Put it all together…. A normal genetic female receives injections of testosterone throughout fetal development. She is born with will be born with: • ovaries. • male internal reproductive ducts. • undeveloped female reproductive ducts. • male external reproductive organs. • all of the above

Puberty • Secondary sexual characteristics • Develop during puberty • Distinguish males and females • Not directly involved in reproduction • For example • Facial hair, deep voice, breasts • Hormonal changes • Anterior pituitary -> growth hormone • Anterior pituitary -> gonadotropic and adrenocorticotropic hormones -> maturation of genitals

Goal review • You should now be able to… • Explain how sexual differentiation occurs • Gonads • Internal reproductive ducts • External reproductive organs • Describe the hormonal changes that occur during puberty and the effect they have on the body

Sample test question Sry protein triggers the development of: • the testes. • a Müllerian system. • the penis. • ovaries.

Sexual differentiation of the brain

Male vs. female brains

Think about it Defend/refute: The differences between the male and female brains in humans are explained by the presence or absence of testosterone during development. 1:00

Think about it Defend/refute: The differences between the male and female brains in humans are explained by the presence or absence of testosterone during development. :30

3:00 Activity 3 • Defend/refute: The differences between the male and female brains in humans are explained by the presence or absence of testosterone during development. • Prepare at least two arguments in support of your decision (i.e. two reasons why you chose to defend/refute this statement)

:30 Activity 3 • Defend/refute: The differences between the male and female brains in humans are explained by the presence or absence of testosterone during development. • Prepare at least two arguments in support of your decision (i.e. two reasons why you chose to defend/refute this statement)

Time’s up! Activity 3 • Defend/refute: The differences between the male and female brains in humans are explained by the presence or absence of testosterone during development. • Defend • Refute • Prepare at least two arguments in support of your decision (i.e. two reasons why you chose to defend/refute this statement)

Activity 3 - Recap • Defend/refute: The differences between the male and female brains in humans are explained by the presence or absence of testosterone during development. • Defend • Refute • Presence/absence of testosterone plays a role, but it is far from the whole story

Activity 3 - Recap • Males have higher levels of androgens, including testosterone (T) • Does T act directly on brain to cause changes? • No

Activity 3 - Recap • Aromatization hypothesis proposes that: • T is converted into estradiol (aromatization) • Causes masculinization • Evidence for aromatization theory • Early estradiol injections -> masculinize brain • If T present, but aromatization blocked -> no masculinization of brain

Activity 3 - Recap • BUT….. • Most of this research was focused on the hypothalamus.. • …of rats! • Why?

Activity 3 - Recap • Aromatization hypothesis is not sufficient • Much more complicated • Aromatization only critical in certain brain areas • Substantial variation between species • Variation in different developmental periods within species • Sex chromosomes exhibit unique, independent effects • Estradiol also plays an active role

Activity 3 - Recap • Take home message • Aromatization hypothesis is not sufficient • Much more complicated • Cause of differentiation varies based on part of brain, species and stage of development • Presence/absence of androgens is not the only important factor

Hormones and behavior • How do hormones affect behavior? • Most of this research is on rodents • Study reproductive behavior • T in females - masculinizes and defeminizes sexual behavior • No T in males – demasculinizes and feminizes sexual behavior • Much more complicated in humans

Masculinization and feminization • Two separate dimensions • NOT opposites • Masculine behavior • Male typical behaviors • Feminine behavior • Female typical behaviors • Can have both at once or neither

Goal review • You should now be able to… • Explain the aromatization hypothesis • Summarize what we understand about sexual differentiation in the mammalian brain, including • Aromatization hypothesis and humans • Key findings in the area

Sample test question The aromatization hypothesis states that: • Testosterone is directly responsible for masculinizing the brain • Male and female brains are not differentiated (i.e. thereare no sex difference in brain development) • estradiol created in the brains of developing males from circulating testosterone masculinizes their brains. • estradiol created in the brains of developing females from circulating testosterone feminizes their brains.

In class assignment 4

Male vs. female? • INDIVIDUAL ICA – Each person should turn in their own answer (make sure to put your name on it!) • Consider what you’ve learned in your reading (including the three case studies at the end of your reading for today – pp. 340 – 342) and in lecture today • How has this influenced your opinion of what makes us male or female? Do you think “male” and “female” are two distinct separate categories? Why or why not? • There is no correct answer, but make sure to support your opinion with a well-reasoned argument based on class material • Put in team folder or bring to front of class.

Hormones and Sexuality – Part 1

Hormones and Sexuality – Part 1

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