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Endo/Repro Exam 1 > 9. Steroid Hormone Biosynthesis > Flashcards

9. Steroid Hormone Biosynthesis Flashcards

1
Q

Steroid hormones are derived from what?

A

cholesterol

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2
Q

What is the path from of steroid synthesis?

A

Cholesterol (27 carbons) -> pregnenolone (21 carbons) via desmolase.

Pregnenolone -> progesterones (THE PRECURSOR TO ALL STERIODS)

Progesterones -> corticosteroids (cortisol and aldosterone) and sex hormones (testosterone (19) and estradoil (18))

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3
Q

What are the other names for desmolase?

A
  • 20, 22 Desmolase
  • Cytochome P450scc
  • CYP11a1
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4
Q

Where is desmolase found?

A

all steroid producing tissue (adrenal, testes, ovaries and placenta)

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5
Q

What catalzyes the 1st and rate-limiting step of steroid hormones

A

desmolase

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6
Q

Desmolase is positively regulated by ____________.

A

ACTH

& LH

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7
Q

What are the short-term and long-term actions of ATCH?

A

Short term: stimulate lipoprotein uptake in cortical cells and increases availability of cholesterol in the adrenal ctx

long term: transcribe genes that code for steroid hormones such as, cytochrome p450scc, which catalyzes the 1st step of steroidogenesis

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8
Q

How is ACTH in a cancer cell?

A
  • In a normal cell, ACTH will bind to Gs GCPR: +AC -> cAMP -> PKA to produce cortisol.
  • In tumor cells, the proportion of cortisol is uncoupled from ACTH.
  • Constituively active PKA will continue to make cortisol even w/o ACTH binding
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9
Q

To go from progesterone -> aldosterone, what CYPS are needed

A

CYP21

CYP11B1

CYP11B2

these are types of cytochrome P450s

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10
Q

To go from progesterone -> cortisol, what CYPS are needed

A

CYP11B1

CYP17

CYP21

these are types of CYTP450

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11
Q

how many cyps in human genome

A

57

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12
Q

Cortisol binds and activates what?

A

glucocorticoid receptor (GR)

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13
Q

Why are glucorticoids inportant in infant respiratory distress syndrome

A
  • During normal delivery, there is a burst of glucocorticoids that alters the bbs lung structure -> makes surfactant -> expands lungs so they can breath.
  • In premature bbs, this process is defective and leads to infant. respiratory distress syndrome. This is prevented by giving mom glucocorticoids.
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14
Q

aldoesterone binds and activates what receptor

A

mineralcorticoid receptor

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15
Q

Patients with congenital adrenal hyperplasia present with what?

A
  1. Hirutism- excessive body hair in M and W where it does not normally grow. F patients will have general oligomenorrhea, which is infrquent menstruation and infertility.
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16
Q

The clinical severity of CAH depends on what?

A

the degree of deficiency in the enzyme that encodes steroidogenisis, causing excess or deficient production of sex steroids.

95% cases involve 21-alpha- hydroxylase. 5% involve 11B-hydroxylase.

17
Q

congential adrenal hyperplasia tx

A

hormone replacement therapy

18
Q

What are the genetics of CAH?

A

Autosomal recessive

19
Q

If a patient has CAH with a mutant 11B-hydroxylase (CYP____), what happens?

A

CYP11B1

  1. Corticosterone precursors build up, causing an excess of androgen productions (M and F sex hormones),
  2. accumulation of 17-alpha- hydroxyprogesterone
  3. accumulation of 11-deoxycorticosterone.
20
Q

Pts with CAH d/t a mutant 11B-hydroxylase will have an increase in 11-deoxycorticosterone. This will cause what?

A
  • 11-deoxycorticosterone is a mineralcorticoid AGO. It will act like aldosterone
  • Cause HTN by promoting increase Na+ and H20 retention, decrease in plasma K+,.
21
Q

In patients with 11-B hydroxylase (Cyp11B1) deficiency, only. ________ and ______ would increase d/t this enzyme deficnecy. Of the two compounds, _________ has a higher affinity for MR to produce HTN.

A
  • 11-deoxycorticosterone
  • 11-deoxyxcortisol
  • Of these two, 11-deoxycorticosterone has a higher affinity for MR to cause HTN.
22
Q

In patients with CAD d/t 21-alpha-hydroxylase deficiency,

what hormones accumulate abnormally?

A
  1. Decreased cortisol synthesis
  2. Decreased aldosterone synthesis -> salt wasting
  3. High ACTH levels

In the blood, progesterone, 17alpha-hydroxypregenolone, 17alpha-hydroxyprogesterone.

23
Q

What are the steroid hormone blood transporter proteins?

where are they made?

A
  1. CBG- corticosteroid binding globulin
  2. SHBG- sex steroid binding globulin

both are made in the liver.

24
Q

__________ is the precursor to the following hormones: progesterne, aldosternoe, cortisol, testosterone and estradiol. Mutations in __________, prevent us from makeing these.

A

Pregnenolone

  1. CYPs
  2. HSDs
  3. Lyases
25
Q

More rare forms of CAH are caused by, _____________, the enzyme that is the gateway to make sex steroid hormones.

A

CYP17A1 (17-alpha-hydroxylase, you will only have aldosterone production.

26
Q

Isolated 17,20-lyase deficiency (ILD), the gateway to make androgens and estrogen sex steroids, causes what?

A
  • No sex steroids; normal levels of glucocorticoids and mineralcorticoids.
  • Does not result in adrenal hyperplasia or HTN.
27
Q

What occurs with ILD?

A
  • Males: underdeveloped genital, intersex, pseuhermaphroditism
  • Females: reduced/no puberty, lack of secondary sex characteristics, child like appearance in adulthood.
28
Q

What converts progesterone -> testosterone?

A

17,20 lyase

29
Q

What stimulates the formation of estradoil and estrone?

A
  • Androstenedione -> [+ FSH] stimulates aromatase in ovaries -> estrone
  • Testosterone -> [+FSH] stimualtes aromatse in ovaries -> estradoil
30
Q

In F, what regulates the production of GnRH?

A

Progesterone inhibits GHR from the hypothalamus, as well as FSH and LH release from the pituitary.

31
Q

In M, what regulates the production of GnRH?

A
  • Testosterone inhibits GnRH
  • Testosterone also inhibits the release of LH from the pituitary gland,
  • Inhibin inhibits the release of FSH
32
Q

Vit D production happens in several different. tissue. What. are. these tissues?

A

1. Skin

2. liver

3. kidney

4. intestine

33
Q

Cholecalciferol (vit D3) is obtained in 2 ways. What are they?

A
  1. Diet
  2. Skin
34
Q

________ is formed exclusively. in the liver by the 25-hyroxylase enzyme (CYP____)

A

25-hydroxycholecalciferol is formed exclusively. in the liver by the 25-hyroxylase enzyme (CYP2R1).

35
Q

Hydroxylation states of vit. D forms what?

A

Cholecalciferol (D3)

Endo/Repro Exam 1 (14 decks)

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