Midterm II: Sex Hormones (Ben) Flashcards Preview

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Flashcards in Midterm II: Sex Hormones (Ben) Deck (21)
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1

What is the starting molecule for synthesis of all sex hormones?

 

DHEA

2

What 3 reactions does 17-hydroxy steroid dehydrogenase (17OHSDH) catalyze?

 

  1. DHEA ---> androstenediol
  2. androstenedione ---> testosterone
  3. estrone ---> estradiol

- All creating more active sex hormone products than the substrates

3

What cofactor does 17OHSDH use?

NADPH

4

What are the 2 androgen reactions catalyzed by 3OHSDH?

What co-factor is used?

  1. DHEA ---> androstenedione
  2. androstenediol ---> testosterone

- using NAD

5

What 2 reactions does aromatase catalyze?

  1. androstenedione ---> estriol
  2. testosterone ---> estradiol

6

What other androgen can be formed from testosterone?

Via what enzyme + cofactor?

5α-dihydrotestosterone

- via 5α reductase

with NADPH

7

What are the 3 isoforms of 17OHSDH?

Where are they + what do they catalyze?

  1. I - in cytosol of placenta, ovaries, adipose tissue
    • estrone ---> estradiol (NADPH)
  2. II - in ER of liverintestine, and placenta
    • oxidates/deactivates testosterone + estradiol (NAD)
  3. III - in ER of testis
    • androstenedione ---> testosterone (NADPH)

8

What cell type is the major site of testosterone synthesis?

What molecular signals stimulate synthesis + how?

Leydig Cells

luteinizing hormone + hCG 

- increase cAMP leading to activation of testosterone synthesis mechanisms

9

What enzyme/activity do Leydig cells lack?

And how does this influence their steroid production?

P45021 

21-OHase activity

- keeps reactions moving towards androgens from pregnenolone

10

How does dihydrotestosterone differ from testosterone?

- binds to testosterone receptors more efficiently + its specific receptor is a better inducer

- can not be converted back to estrogens

11

Where is the aromatase reaction located?

Cell types + intracellular location.

in ovariesplacentaadipose tissue, and bones

in the sER

12

What is the 2 cell theory in relation to estrogen production?

What 2 cell types are involved and what do they make?

  1. Theca Interna - produce weak androgens from cholesterol 
    • 17-OHase, 17,20 Lyase
    • ​no P450c21, 17-OHSDH, aromatase
  2. Granulosa Cells - produce estradiol from androstenedione
    • 17-OHSDH, aromatase
    • no 17-OHase or 21-OHase

13

What hormones stimulate each of the two types of ovary cells necessary for estrogen production?

  • Theca interna cells - luteinizing hormone (LH)
  • Granulosa cells - follicle-stimulating hormone (FSH)

14

What happens to the two types of estrogen-producing cells in the ovary during the luteal phase?

  • theca cells - lose 17-OHase/17,20 lyase activity
  • granulosa cells - lose aromatase activity

 

- both switch to just producing progesterone from cholesterol

15

What is the common condition resulting in ovarian cysts?

How does it occur?

What non ovary-related symptoms is it associated with?

Polycystic Ovarian Syndrome

- via hyperandrogenism when theca cells increase + express more LH receptors ---> androgen increase

- causes lack of ovulation and antral follicle retention (=cysts)

- associated with obesity + insulin resistance

16

What is the name for the estrogen-like compounds which can have tissue-specific actions?

Describe their action.

SERMs

(Selective Estrogen Receptor Modulators)

- interact with estrogen receptors + induce conformational change

- depending on tissue, can be agonist OR antagonist

17

What is an important synthetic SERM?

What are its actions?

What are its negative side effects?

Tamoxifen

- agonist in bones - prevents osteoporosis

- antagonist in breast tissue - breast cancer therapy

- side effect: partial agonist in endometrium - increases endometrial cancer risk

18

Name an important endogenous SERM.

What are its effects?

27-OH-Cholesterol

- promotes breast cancer proliferation

- decreases bone density

- increases risk of cardiovascular disease

19

What is the sex hormone synthesis function of the placenta?

Produces estradiol

- acts like a granulosa cell

- uses DHEA-sulfate from maternal/fetal adrenal cortex

20

What does the placenta lack for steroid hormone synthesis that forces it to rely on fetal/maternal precursors?

SF-1 (Steroidogenic Factor 1) 

21

What sex hormone is primarily created in the fetal liver + adrenal cortex and is an even stronger version than any synthesized in adults?

Estriol

- stronger estrogen than estradiol