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GIGU > Steroid Biosynthesis > Flashcards

Steroid Biosynthesis Flashcards

1
Q

What are all steroid hormones synthesized from?

A

Cholesterol

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2
Q

What enzyme controls the rate-limiting step of steroid hormone synthesis?

A

Desmolase

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3
Q

Desmolase activity is regulated by?

A

ACTH

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4
Q

What reaction is catalyzed by Desmolase?

A

Cholesterol –> Pregnenolone

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5
Q

Pregnenolone can then go on to create what other steroid hormones?

A

Aldosterone
Cortisol
Sex hormones - testosterone, estradiol, progesterone

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6
Q

Where does steroid hormone synthesis take place?

A

Adrenal cortex

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7
Q

Aldosterone can bind and activate what receptor?

A

Mineralcorticoid Receptor (MR)

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8
Q

Activation of the Mineralcorticoid Receptor results in what?

A

Increased Na+ retention = hypertension!

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9
Q

Primary Aldosteronism/Conn’s Syndrome

A

Adrenal glands produce too much Aldosterone!

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10
Q

Too much Aldosterone results in?

A

Retention of Na+
Loss of K+
Body holds on to too much water
Increased blood volume and blood pressure

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11
Q

Main result of Primary Aldosteronism/Conn’s Syndrome?

A

INCREASED BLOOD PRESSURE

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12
Q

Adrenal Hyperplasia

A

Deficiencies in adrenal enzymes that are used to make glucocorticoids
– This causes an increase in both cortisol PRECURSORS and androgens (sex hormones)

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13
Q

What are some signs of adrenal hyperplasia?

A

Life-threatening infections
Acne, short stature
Hirsutism
Oligomenorrhea and Infertility

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14
Q

Hirsutism

A

Male pattern body hair on women - seen with adrenal hyperplasia

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15
Q

Oligomenorrhea

A

Infrequent or light menstrual cycles - seen with adrenal hyperplasia

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16
Q

Cholesterol is converted to Pregnenolone

Pregnenolone is then converted to what 2 things?

A

Progesterone AND 17OH-progesterone

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17
Q

Progesterone is converted to what?

A

11-deoxycorticosterone

18
Q

17OH-progesterone is converted to what?

A

11-deoxycortisol

19
Q

What enzyme is responsible for creating 11-deoxycorticosterone and 11-deoxycortisol?

A

21-hydroxylase

20
Q

11-deoxycorticosterone is converted to what?

A

Aldosterone

21
Q

11-deoxycortisol is converted to what?

A

Cortisol

22
Q

What enzyme is responsible for creating Aldosterone and Cortisol?

A

11beta - hydroxylase

23
Q

Adrenal hyperplasia can be seen with the loss of what enzymes?

A

21 - hydroxylase

11beta - hydroxylase

24
Q

11beta - hydroxylase deficiency

A

DECREASED aldosterone and cortisol

INCREASED 11-deoxycorticosterone and 11-deoxycortisol

25
Q

11beta - hydroxylase deficiency results in what main symptom and why?

A

HIGH BLOOD PRESSURE because 11-deoxycorticosterone also has a high affinity to bind to the same receptor as aldosterone (MR)
– Thus you have high blood pressure even without the formation of aldosterone

26
Q

What is the HPA for steroid hormones, specifically cortisol?

A

Hypothalamus - CRH
Anterior pituitary - ACTH
Adrenal glands - Cortisol
- Cortisol has (-) feedback on both CRH and ACTH

27
Q

ACTH binds to what type of receptor in the Zona Fasciculata in the adrenal glands?

A

GPCR

28
Q

What is the intracellular pathway events after ACTH binds to a GPCR in the adrenal gland?

A

Stimulates Adenylyl Cyclase
Increases cAMP
Activates protein kinase A
Creates cortisol

29
Q

In a tumor cell, what is always active in the ACTH mediated intracellular signaling pathway?

A

protein kinase A

30
Q

17,20 Lyase deficiency

A

Deficient production of androgens and 46XY development

31
Q

Cholecalciferol (D3) can be formed in what 2 places in the body?

A

Skin and intestines

32
Q

The skin creates D3 using?

A

7-dehydrocholesterol + UV light

33
Q

The intestines creates D3 using?

A

D2 (Ergocalciferol)

34
Q

Cholecalciferol (D3) is then transported from the skin and intestines to?

A

Liver

35
Q

The liver takes cholecalciferol (D3) to?

A

25-hydroxycholecalciferol

36
Q

The liver creates 25-Hydroxycholecalciferol using what enzyme?

A

25-hydroxylase

37
Q

25-hydroxycholecalciferol is then sent to where?

A

Kidney

38
Q

The kidney takes 25-hydroxycholecalciferol to what?

A

1,25 - dihydroxycholecalciferol = calcitriol

39
Q

The kidney uses what enzyme to create calcitriol, the active form of Vitamin D?

A

1alpha-hydroxylase

40
Q

What is the active form of Vitamin D?

A

1,25-dihydroxycholecalciferol (calcitriol)

41
Q

Where is the active form of Vitamin D synthesized?

A

Kidney

GIGU (29 decks)

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