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GIGU > Steroid Biosynthesis > Flashcards

Steroid Biosynthesis Flashcards

1
Q

What can you inject infants to prevent RDS?

A

glucocorticoids

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2
Q

What drops before labor and menstruation and opens Ca++ channels in spermatozoa?

A

progesterone

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3
Q

All steroid hormones are synthesized from _____ in the _____

A

cholesterol

adrenal cortex

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4
Q

What RLS converts cholesterol to pregnenolone?

A

desmolase

–>cytochrome P450 family

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5
Q

What stimulates desmolase activity?

A

ACTH

–>cholesterol to pregnenolone (adds C=O)

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6
Q

Where is desmolase found?

A

all steroid-producing tissues

–>adrenal, testes, ovary, placenta

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7
Q

What is the most important biochemical intermediate that is used as a substrate for steroid hormone synthesis?

A

pregnenolone

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8
Q

What can be made from pregnenolone?

A 
progesterone
aldosterone
cortisol
testosterone
estradiol
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9
Q

What binding protein transports most steroid hormones in circulation?

A

sex hormone binding globulin (SHBG) and albumin

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10
Q

What mineralocorticoid does Angiotensin II stimulate?

A

Aldosterone

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11
Q

What group of conditions are characterized by deficiencies in adrenal enzymes used to synthesize glucocorticoids?

A

adrenal hyperplasias

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12
Q

What are consequences of adrenal hyperplasia?

A
  • life-threatening sinus and pulmonary inf
  • orthostatic syncope
  • shortened stature
  • severe acne
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13
Q

What are sx women experience with mild congenital adrenal hyperplasia?

A

hirsutism
general oligomenorrhea
infertility

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14
Q

How to determine if fetus is at risk for congenital adrenal hyperplasia?

A
  • human leukocyte antigen haplotype

- excess cortisol precursors in amniotic fluid

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15
Q

What can be used as treatment for adrenal hyperplasia

A

Hormone replacement therapy

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16
Q

What enzyme deficiencies can cause adrenal hyperplasia?

A

21-hydroxylase
–> no aldosterone
11-B hydroxylase
–> no cortisol

17
Q

What does a 21-hydroxylase deficiency cause buildup of?

A

progesterone
–>aldosterone pathway
17 hydroxyprogesterone
–>cortisol pathway

18
Q

What does a 11B- hydroxylase deficiency cause buildup of?

A

Deoxycorticosterone
–>aldosterone pathway

11-Deoxycortisol
–>cortisol pathway

19
Q

Describe primary aldosteronism?

A

adrenal cortex produces too much aldosterone

  • -> retention of sodium and water to extreme levels
  • ->excretion of H and K

HTN

20
Q

Describe Conn Syndrome

A

–>type of primary aldosteronism

excess secretion of aldosterone

retention of sodium

loss of potassium

HTN

21
Q

All steroids that activate mineralocorticoid receptors cause what?

A

retention of sodium

–>HTN

22
Q

How does 11-B hydroxylase deficiency cause HTN?

A

decreased aldosterone synthesis, however deoxycorticosterone has high affinity for mineralocorticoid receptor–> retention of Na and HTN

23
Q

What glucocorticoid causes immunosuppression?

A

cortisol

–> gets rid of NF-kB

24
Q

What does ACTH stimulate the production of?

A

cortisol

–>when level falls, CRH->ACTH->cortisol in fasciculata

25
Q

How does ACTH activate secretion of cortisol?

A

it is a G protein, so:

adenylyl cyclase–> cAMP–>protein kinase A

26
Q

How does a tumor cell bypass activation by ACTH to produce cortisol?

A

PKA (protein kinase A)

constituitively active

27
Q

In addition to activating cortisol production, what else does ACTH influence?

A

steroid hormone secretion
–> + cholesterol delivery to mito where desmolase is

transcription of genes encoding for steroidogenic enzymes

28
Q

What enzyme is crucial to the steroid hormone pathway?

A

17,20-lyase

–>AKA CYP17A1

29
Q

What are the precursors of androgen production?

A

17-a-hydroxyprogesterone

hydroxypregenolone

30
Q

Where is 25-hydroxycholecalciferol exclusively found?

A

liver

31
Q

Where is calcitrol synthesized?

A

active form of vitamin D

kidney via 1a-hydroxylase

32
Q

What does 7-dehydrocholesterol make?

A

found in skin

vitamin D3 (cholecalciferol)

33
Q

How do you get low aldosterone and high androgens?

A

11-B hydroxylase deficiency

–>since can’t make aldosterone or cortisol, intermediates shift to androgen pathway

GIGU (37 decks)

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