Steven Crane Compiled Section Handouts. Human Behavioral Biology 2012

How Perinatal Hormones Affect Sexual Behavior

What is a "feminized" brain vs. "masculinized" brain? How accurate is this dichotomy?

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  Feminized: Hypothalamic gonadal hormone signaling is cyclic (ovulation, menstruation, etc)
  
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  Masculinized: produces male reproductive FAPs like erections and pelvic thrusts
  
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  Tons of animals fall in-between. An artificial dichotomy.
  

Through what pathways does T have its effects?

• Peripheral body effects: converted to DHT and influences sensation.

• Few areas of the brain: acts just as T, no conversion.

• Most areas of the brain: is converted to estrogen and binds to estrogen receptors.

How do females avoid a masculinized brain?

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  They would have one because of all the estrogen floating around their prenatal environment
  
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  But estrogen is pulled out of fetal circulation by alpha-feto protein
  

In what cases are females "masculinized." And what are their outcomes?

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  Two ways:
  

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  DES drug exposure generates high androgen levels during pregnancy
  
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  Congenital adrenal hyperplasia
  

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  Outcomes:
  

^o Less interest in "female-typical" sexual behavior and roles. More likely to be gay.

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  Confounds: many reconstructive genital surgeries and being a taller, more muscular woman
  

What is the case of testicular feminized males? How do their bodies and brains develop?

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  Born XY (genetically male) but androgen receptor mutates. T doesn't have bodily effects (as DHT).
  
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  But in brain T is converted to estrogen and thus produces a masculinized brain.
  
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  Male secondary sexual characteristics emerge at pubertyGender identity and bodily characteristics usually remain female.
  

Do gay men have "feminized" brains? Why yes? Why no?

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  Yes: more older brothers increases likelihood of being gay because mother has antibodies that target T. Less T on board, therefore a "demasculinized" brain.
  
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  Probably no: gay men have a lot more sex (look more "masculinized" than straight men in that respect).