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Block 17 Endocrinology Module 3 > Steroidogenesis and Metabolism > Flashcards

Steroidogenesis and Metabolism Flashcards

1
Q

any of various compounds containing a 17-carbon 4-ring system and including the sterols and the numerous hormones and glycosides

A

Steroid

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2
Q

lipid structure consisting of 4 linked hydrocarbon rings forming the bulky steroid structure and a hydrocarbon tail linked to one end of the steroid and a hydroxyl group linked to the other end.

A

Cholesterol

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3
Q

Steroidogenesis can occur in what organs

A

Adrenal cortex, testes, ovaries, ovarian corpus luteum, and the placenta

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4
Q

This protein is essential for the transport of cholesterol to P450scc in the inner mitochondrial membrane

A

StAR – Steroidogenic acute regulatory protein

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5
Q

All mammalian steroid hormones a re formed from cholesterol via ______ thru a series of reactions

A

Pregnenolone

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6
Q

What are the steroids made in zona glomerulosa

A

Mineralocorticoids (principal product is aldosterone)

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7
Q

What are the steroids made in zona fasciculata

A

Glucocorticoids esp cortisol

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8
Q

What are the steroids made in zona reticularis

A

Androgens – dehydroepiandrosterone

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9
Q

Major regulator of salt balance

A

Aldosterone

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10
Q

Shape of the right adrenal gland

A

Pyramidal

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11
Q

Shape of the left adrenal gland

A

Cresentic

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12
Q

Enzymes involved in steroidogenesis are found either in _____ or _____

A

Mitochondria or in the cytoplasmic reticulum

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13
Q

This is a smooth ER enzyme that acts upon either progesterone or more commonly pregnenolone

A

17 a-hydroxylase

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14
Q

Most potent natural glucocorticoid hormone in humans

A

Cortisol

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15
Q

11B hydroxylase is a _____ enzyme

A

Mitochondrial

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16
Q

Synthesis of aldosterone follows the mineralocorticoid pathway and occurs in the

A

Zona glomerulosa

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17
Q

Pregnenolone is converted to progesterone by the action of what enzymes?

A

3a-hydroxysteroid dehydrogenase (3a-OHSD) and δ5,4-isomerase.

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18
Q

How does K ions exert a stimulatory effect on aldosterone secretion?

A

K ions cause depolarization of the z. glomerulosa cells, allowing Ca ions to enter. The increase in intracellular Ca fuels the Ca dependent intracellular events triggered by angiotensin II

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19
Q

Main extracellular stimuli which regulate aldosterone secretion

A

Ang II, K+, and ACTH

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20
Q

The major androgen or androgen precursor produced by the adrenal cortex is

A

Dehydroepandrosterone (DHEA)

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21
Q

Most potent adrenal androgen

A

Testosterone

22
Q

Reduction of adrostenedione at the C17 position results in the formation of

A

Testosterone

23
Q

What is the adrenogenital syndrome

A

Adrenal androgen production increases markedly if glucocorticoid biosynthesis is impeded by the lack of one of the hydroxylases

24
Q

2 pathways where testosterone is metabolized

A

Oxidation at the 17 position

Reduction of the A ring double bond and the 3 ketone

25
Q

Among the 2 pathways where testosterone is metabolized, which is the more efficient one?

A

The oxidation at the 17 position

26
Q

Most significant metabolic product of testosterone

A

DHT

27
Q

Dihydrotestosterone is formed from testosterone through action of which enzyme

A

5a reductase

28
Q

90% of testosterone produced is ozidized into

A

17 ketosteroids

29
Q

Testicular androgens are synthesized in the interstitial tissue by the

A

Leydig cells

30
Q

The immediate precursor of the gonadal steroids, as for the adrenal steroids,

A

Cholesterol

31
Q

The conversion of cholesterol to pregnenolone in the ovary and the testis is promoted by

A

LH

32
Q

The rate limiting step in testicular steroidogenesis is

A

Delivery of cholesterol to the inner membrane of the mitochondria by StAR

33
Q

Pregnenolone can also be converted to testosterone by what pathway

A

Dehydroepiandrosterone or

Δ5 pathway

34
Q

T or F conversion of estrogens occurs mainly in the adrenal cortex

A

F: it is more in the peripheral tissues and ovaries

35
Q

Primary estrogen of ovarian origin

A

17B estradiol

36
Q

Estriol is produced from the

A

Placenta

37
Q

This is formed if the substrate of the aromatase enzyme complex is testosterone

A

Estradiol

38
Q

These are the source of androstenedione and testosterone

A

Theca cells

39
Q

Only steroid that is not bound to protein

A

Aldosterone

40
Q

Major site of cortisol metabolism

A

Liver

41
Q

Estrone and estradiol and their metabolites undergo which reactions

A

Sulfation by sulfotransferases and

Glucoronidation by glucoronyltransferases

42
Q

The catecholamines are synthesized from tyrosine in the

A

Chromafin cells of the adrenal medulla

43
Q

Major product of the adrenal medulla is

A

Epinephrine

44
Q

The conversion of tyrosine to epinephrine requires four sequential steps

A

Ring hydroxylation
Decarboxylation
Side chain hydroxylation to form norepi
N-methylation to form epi

45
Q

Immediate precursor of catecholamines

A

Tyrosine

46
Q

Rate limiting enxyme in catecholamine biosynthesis

A

Tyrosine hydroxlase

47
Q

T or F catecholamines can cross the BBB that’s why there’s enough supply to the brain from the systemic circulation

A

F: catecholamines can’t cross the BBB that’s why they must be synthesized locally

48
Q

Precursor of dopamine that can cross the BBB

A

L-dopa

49
Q

DBH uses ____ as electron donor; ____ at the active site and _____ as modulator

A

Ascorbate- electron donor
Copper at active site
Fumarate – modulator

50
Q

Conversion of norepi to epi occurs in the

A

Cytoplasm

51
Q

PNMT catalyzes the N-methylation of norepinephrine to form epinephrine in the

A

Epinephrine forming cells of the adrenal medulla

Block 17 Endocrinology Module 3 (1 decks)

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