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MNE - Exam 2 > Lecture 32-Sex Steroid Synthesis > Flashcards

Lecture 32-Sex Steroid Synthesis Flashcards

1
Q

Where else is pregnenolone synthesized and how is it different here?

A
  • testes, ovaries

- LH-stimulated instead of ACTH

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2
Q

Why do the testes favor androgen synthesis?

A

because there are no MCC or GCC enzymes available

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3
Q

What part of the testes produce testosterone? What does this testosterone do?

A

Leydig cells

  • inhibits: GnRH, LH, FSH
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4
Q

List the inputs to Leydig cells

A

LH: stimulates testosterone synthesis
FSH: stimulates upregulation of LH Rs

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5
Q

List the inputs to Sertoli cells

A

FSH: synergizes with testosterone from Leydig cells (high concentrations of testosterone are being produced for spermatogenesis) to synthesize ABP (same peptide sequence as TeBG but different glycosylation pattern)

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6
Q

What is the function of ABP?

A

It binds testosterone from Leydig cells in the seminiferous tubules and creates high local concentrations of testosterone to help with spermatogenesis

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7
Q

TeBG is synthesized in response to ______ (3).

A
  • high estrogens
  • liver disease
  • hyperthyroidism
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8
Q

What are the carriers for:

  • testosterone
  • DHT
  • estradiol
  • estrone
  • progesterone
A
  • testosterone: TeBG, albumin (1-3% free)
  • DHT: TeBG (1% free)
  • estradiol: TeBG, albumin (weak)
  • estrone: albumin
  • progesterone: CBG
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9
Q

What are the general functions of testosterone (3)?

A
  • spermatogenesis
  • gonadotropin regulation
  • Wolffian stimulation
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10
Q

What are the general functions of DHT? (3)

A
  • External virilization
  • sexual maturation at puberty
  • does NOT play a role in spermatogenesis!!!
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11
Q

Primary Hypogonadism

A
  • usually genetic deficiency of an enzyme involved in testosterone synthesis (testicular failure)
  • depending on when it arises it can result in regression or failure to develop 2º sex characteristics
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12
Q

Secondary hypogonadism

A
  • testicular failure via failure of the pituitary to produce gonadotropins
  • same results as 1º hypogonadism
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13
Q

5 alpha reductase deficiency

A
  • no 5alpha reductase
  • internal genitalia male: will produce androgen during puberty that will cause masculinization
  • external genitalia, up until puberty, appear female
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14
Q

For someone with 5 alpha reductase deficiency, what happens at puberty and what are they like as an adult?

A
  • penis growth
  • testes descend
  • urethra remains
  • penis growth with DHT
  • urethra remains in female position
  • labia fuse
  • blind ended vaginal pouch
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15
Q

Complete Androgen sensitivity (testicular feminization)

A
  • XY males with no androgen receptors
  • external female genitalia (blind ended vaginal pouch; no pubic hair though due to the androgen insensitivity)
  • inguinal testes
  • uninhibited stimulation of testosterone production by hypothalamus and pituitary since they don’t have receptors for it
  • high androgen overflows into aromatase reaction causing breast development from the estradiol
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16
Q

Partial Androgen Insensitivity

A
  • some residual androgen receptor activity
  • symptoms vary depending on severity of disease
  • overproduction of androgens due to lack of receptors on hypothalamus and pituitary
17
Q

Other than aromatase, what is required for testosterone conversion to estradiol?

A
  • microsomal P450 complex that requires 3 NADPH and 3 Oxygens)
18
Q

Where are estrogen and progesterone produced in the ovaries?

A
  • progesterone: granulosa cells–NO 17ALPHA HYDROXYLASE
  • estrogen: theca cells (from aromatase and testosterone). Theca cells also produce androstenedione, testosterone and progesterone
19
Q

In the ovaries, LH stimulates _____ (2)

A
  • P450SCC activity for both theca and granulosa cells

- 17 alpha hydroxylase

20
Q

In the ovaries, FSH stimulates______ (2)

A
  • P450SCC

- androstenedione –> estriol

21
Q

Where is aromatase?

A

brain, skin and fat

- 80% of male estrogen synthesized in the periphery

22
Q

How do fetuses produce androgens? (progesterone and estrogen)

A
  • cholesterol –> DHEA-3-sulfate in adrenal
  • DHEA-3-sulfate –> 16alpha hydroxyDHEA in liver
  • 16alpha hydroxyDHEA –> estriol in placenta
  • pregnenolone –> progesterone in placenta
  • progesterone –> cortisol in adrenal

MNE - Exam 2 (17 decks)

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