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Biochemistry II > Sex hormones (Ben) > Flashcards

Sex hormones (Ben) Flashcards

1
Q

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

A

DHEA

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2
Q

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

A
  1. DHEA → androstenediol
  2. androstenedione → testosterone
  3. estrone → estradiol
  • All creating more active sex hormone products than the substrates
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3
Q

What cofactor does 17OHSDH use?

A

NADPH

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4
Q

What are the 2 androgen reactions catalyzed by 3OHSDH?

What co-factor is used?

A
  1. DHEA → androstenedione
  2. androstenediol → testosterone
  • using NAD
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5
Q

What 2 reactions does aromatase catalyze?

A
  1. androstenedione → estrone
  2. testosterone → estradiol
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6
Q

What other androgen can be formed from testosterone?

Via what enzyme + cofactor?

A

5α-dihydrotestosterone

  • via 5α reductase

with NADPH

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7
Q

What are the 3 isoforms of 17OHSDH?

Where are they + what do they catalyze?

A
  1. I - in cytosol of placenta, ovaries, adipose tissue
    • estrone —> estradiol (NADPH)
  2. II - in ER of liver, intestine, and placenta
    • oxidates/deactivates testosterone + estradiol (NAD)
  3. III - in ER of testis
    • androstenedione —> testosterone (NADPH)
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8
Q

What cell type is the major site of testosterone synthesis?

What molecular signals stimulate synthesis + how?

A

Leydig Cells

  • luteinizing hormone + hCG
  • increase cAMP leading to activation of testosterone synthesis mechanisms
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9
Q

What enzyme/activity do Leydig cells lack?

And how does this influence their steroid production?

A

P45021

21-OHase activity

  • keeps reactions moving towards androgens from pregnenolone
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10
Q

How does dihydrotestosterone differ from testosterone?

A
  • binds to testosterone receptors more efficiently + its specific receptor is a better inducer
  • can not be converted back to estrogens
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11
Q

Where is the aromatase reaction located?

Cell types + intracellular location.

A

in ovaries, placenta, adipose tissue, and bones

in the sER

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12
Q

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

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

A
  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
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13
Q

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

A
  • Theca interna cells - luteinizing hormone (LH)
  • Granulosa cells - follicle-stimulating hormone (FSH)
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14
Q

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

A
  • theca cells - lose 17-OHase/17,20 lyase activity
  • granulosa cells - lose aromatase activity
  • both switch to just producing progesterone from cholesterol
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15
Q

What is the common condition resulting in ovarian cysts?

How does it occur?

What non ovary-related symptoms is it associated with?

A

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
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16
Q

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

Describe their action.

A

SERMs

(Selective Estrogen Receptor Modulators)

  • interact with estrogen receptors + induce conformational change
  • depending on tissue, can be agonist OR antagonist
17
Q

What is an important synthetic SERM?

What are its actions?

What are its negative side effects?

A

Tamoxifen

  • agonist in bones - prevents osteoporosis
  • antagonist in breast tissue - breast cancer therapy
  • side effect: partial agonist in endometrium - increases endometrial cancer risk
18
Q

Name an important endogenous SERM.

What are its effects?

A

27-OH-Cholesterol

  • promotes breast cancer proliferation
  • decreases bone density
  • increases risk of cardiovascular disease
19
Q

What is the sex hormone synthesis function of the placenta?

A

Produces estradiol

  • acts like a granulosa cell
  • uses DHEA-sulfate from maternal/fetal adrenal cortex
20
Q

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

A

SF-1 (Steroidogenic Factor 1)

21
Q

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

A

Estriol

  • stronger estrogen than estradiol

Biochemistry II (16 decks)

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