Sex Differences Flashcards
(29 cards)
Name four sex differences in humans.
- Hormones & receptors
- Weight & size
- Fat distribution
- Regulation of emotions
What is the SRY gene ?
- Sex-determing region of the Y-chromosome
- It leads directly to the process of male sexual differentiation
Which differentiation is triggered by the SRY ?
- Differentiation of precursor cells into Sertoli cells
- Differentiation of gonade into testes
Which differentiation is triggered by the absense of SRY ?
- Differentiation of precursor cells into Granula cells
- Differentiation of gonade into ovaries
Which hormones are produced by the testes after the expression of the SRY gene ?
- Testosterone
- Dihydrotestosterone (DHT)
- Anti-Müllerian hormone (AMH)
When and for which effect is the first gonadal estrogen secreted ?
- During puberty
- Leads to the development of secondary sexual characteristics
In which organ belong Sertoli cells and which hormone are they producing ?
- In testes
- They produce Anti-Müllerian hormone (AMH)
In which organ belong Leydig cells and which hormone are they producing ?
- In testes
- They produce testosterone
What is the effect of the secretion of AMH ?
The regression of the Müllerian duct development
What is the effect of the secretion of testosterone in the early sex differentiation ?
The promotion of the Wolffian duct development
Describe the secrection pattern of testosterone in male mice until the end of their puberty.
- Testosterone level increases 18 days before birth and drops to zero 3 days after birth
- Level increases again a few days before the start of puberty
- Puberty starts arround 30 days after birth and from now on the testosterone level stays stable
Describe the secrection pattern of estrogen in female mice until the end of their puberty.
- No estrogen is secreted during birth and childhood
- Estrogen level increases a few days before the start of puberty (~day 25 after birth)
- In and after puberty the estrogen level increases and decreases slightly following the mentrual cycle
What are the two phases of sex differentiation in the brain ?
- Organization of sex differences in the brain
- Happens the days arround birth
- Is caused by testosterone secretion in males and missing sex hormone secretion in females - Activation of sex differences in the brain
- Happens during puberty
- Is caused by the increased level of testosterone in males and estrogen in females
Describe shortly the HPG axis with its most important organs and hormones.
- Hypothalamus secretes GnRH, which activates the pituitary
- Pituitary secretes LH and FSH, thereby FSH activates the Gonades
- Gonades produce and secrete sex hormones (androgen and estrogen)
What enzyme is the key player in converting andogens into estrogens ?
- Aromatase P450
- It is encoded by the CYP19 gene
In which tissues is aromatase expressed ?
- Ovaries
- Testes
- Placenta
- Adipose tissue
- Brain
Name the three metabolic convertions which are catalyzed by aromatase.
- Androstenedione into Estrone
- Testosterone into Estradiol
- 16α-OH-DHEAS into Estriol
Which effects can be caused by an aromatase deficiency in females ?
- Genital ambiguity
- Pubertal failure
- Multicystic ovaries
- Lack of ovulation
- Infertility
What are the reasons for Hypergonadotropic Hypogonadism ?
- Gonads are not working correctly and produce less sex hormones
- Low level of sex hormones leads to a lack of negative feedback
- Pituitary increase the secretion of LH and FSH
What are the symptoms of Hypergonadotropic Hypogonadism in adults ?
- Low or absent sex drive
- Fatigue and low energy
- Difficulty to stay concentrated
- Hair loss
- Hot flashes
What are the symptoms of Hypergonadotropic Hypogonadism in adolescents ?
- Delayed onset of puberty
- Lack of facial or body hair development
- Shortness of stature
- Underdeveloped testes and penis
- Absent or irregular periods
- Low sex drive
What is the function of aromatase in the placenta ?
- Convertion of DHEAS into estrogen
- Prevention excess androgen exposure
Placental sulfatase and 17β-hydroxysteroid dehydrogenase can act in the absense of aromatase. What is its function in this case ?
- Convertion of DHEAS into testosterone
- Virilization / masculinization of female external genitalia during early embryonic life
What is the function of AFP ?
- AFP binds estradiol with a high affinity
- It prevents estradiol from crossing the blood-brain barrier and acting on estrogen receptors in the female brain
- AFP protects the female from masculinization during development
