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GI/GU Exam > Steroid Biosynthesis > Flashcards

Steroid Biosynthesis Flashcards

1
Q

What regulates cholesterol desmolase activity?

A

ACTH

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2
Q

What does cholesterol desmolase do?

A

converts cholesterol to pregnenolone (committed step)

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3
Q

What tissues is cholesterol desmolase found in? (4)

A
  • adrenals
  • testes
  • ovary
  • placenta

All steroid-producing tissues!

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4
Q

What is the most important biochemical intermediate?

A

pregnenolone

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5
Q

What role does progesterone play in pregnancy? (correlation box)

A
  • It regulates voltage-gated Ca2+ channels on spermatozoa
  • prepares uterus for implantation
  • causes smooth muscle relaxation
  • decreases maternal immune response

basically supports pregnancy, and decreases prior to menstruation, labor, and lactation

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6
Q

How are glucocorticoids and infant respiratory distress syndrome related (IRDS)? (correlation box)

A
  • normally burst of glucocorticoids prior to birth causes production of surfactant
  • preemie’s don’t have this, get IRDS unless glucocorticoids given to mother before birth
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7
Q

Metabolic modulation of steroid hormones is important for what? (correlation box)

A
  • Not OD’ing yourself on mineralocorticoids or glucocorticoids
  • changes affinity of hormone for receptor so you don’t get overeffect (like too much Na/H20 retention)
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8
Q

What globulin is progesterone carried on? (correlation box)

A

CBG (corticosteroid-binding globulin)

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9
Q

How does cortisol suppress the immune system? (correlation box)

A

It inhibits the transcription factor that activates NF-KB, inhibiting B cell response and apoptosing T cells.

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10
Q

What disorders are associated with vitamin D? Why? (correlation box)

A
  • brittle bones/ rickets in kids

- osteomalacia / several fx’s in adults

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11
Q

What can adrenal hyperplasia cause in women? (3)

A
  • hirsutism
  • general oligomenorrhea
  • infertility
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12
Q

What is adrenal hyperplasia caused by? (2)

A
  • deficiencies in the adrenal enzymes used to synthesize corticosteroids
  • increased production from adrenal gland of both cortisol precursors and androgens
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13
Q

What two enzyme deficiencies can cause adrenal hyperplasia?

A
  • 21 hydroxylase

- 11-beta hydroxylase

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14
Q

What does a 21 - hydroxylase deficiency result in a buildup of? (2)

A
  • progesterone

- 17-hydroxyprogesterone

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15
Q

What is another name for 21 - hydroxylase?

A

CYP21A2

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16
Q

What does a 11-beta hydroxylase deficiency result in a buildup of? (2)

A
  • deoxycorticosterone

- 11-deoxycortisol

17
Q

What is another name for 11-beta hydroxylase?

A

CYP11B1

18
Q

What can a deficiency of CYP11B1 result in, physiology-wise?

A
  • hypertension and high testosterone, because 11-deoxycorticosterone can act as a ligand in the aldosterone pathway
19
Q

What can a deficiency of CYP21A2 result in, physiology-wise?

A
  • low blood pressure and high testosterone, because progesterone CAN’T act as a ligand, and you get no aldosterone effect
20
Q

What is primary aldosteronism also known as?

A

Conn’s syndrome

21
Q

What does aldosterone do?

A

Promotes excretion of H+ and K+

22
Q

What are the symptoms of Conn Syndrome? (4)

A
  • excessive aldosterone secretion
  • retention of sodium
  • loss of potassium
  • hypertension
23
Q

What hormones increase sodium retention? (5)

A
  • aldosterone
  • 11-deoxycorticosterone
  • testosterone
  • cortisol
  • cortisone
24
Q

What is the physical manifestation of 11 - beta hydroxylase deficiency?

A
  • virilization
25
Q

How do tumor cells affect cortisol production?

A
  • they cause its release in the absence of any ACTH stimulation
26
Q

What is another name for 17, 20-lyase?

A

CYP17A1

27
Q

What do mutations in 17, 20-lyase cause?

A

deficiency in androgens and estrogens

28
Q

What two ways is vitamin D3 obtained?

A
  • absorbed through intestine as ergocalciferol

- converted from 7-dehydrocholesterol in the skin

29
Q

Where is 25-hydroxycholecalciferol found?

A

in the liver exclusively

30
Q

What is the pathway of Vitamin D3 synthesis?

A

cholecalciferol → 25-hydroxycholecalciferol → 1,25-dihydroxycholecalciferol

31
Q

What enzyme converts cholecalciferol to 25-hydroxycholecalciferol?

A

25-hydroxylase

32
Q

What enzyme converts 25-hydroxycholecalciferol to 1,25-dihydrocholecalciferol?

A

1-alpha-hydroxylase

33
Q

Where does the final step of Vit D3 synthesis occur?

A

kidney

GI/GU Exam (21 decks)

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