Steroid Hormones Flashcards Preview

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Flashcards in Steroid Hormones Deck (54)
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1

What is the precursor for steroid hormones?

Cholesterol

2

What happens to cholesterol during steroid hormone synthesis?

C atoms undergo redox reactions

3

To what are cytochrome P450 enzymes bound within the cell?

Mitochondrial/endoplasmic reticulum membranes

4

What do cytochrome P450 enzymes contain?

Haeme group

5

What type of reaction are cytochrome P450 enzymes involved in during the synthesis of steroid hormones?

Reduction using NADPH
Hydroxylation of C-H bond to C-OH
- For some, coupled with cleavage of C-C bond

6

What happens in the first step of steroid hormone biosynthesis?

Cholesterol side chain cleavage enzyme (cholestero SCC) converts cholesterol > pregnenolone

7

What is the first intermediate of steroid hormone synthesis?

Pregnenolone

8

What do hydroxysteroid dehydrogenases (HSD) do?

Catalyse interconversion of C-OH to C=O
Reduction reaction using NADH

9

What are the major pituitary hormones regulating steroid hormone synthesis?

ACTH
LH
FSH

10

What hormone has a negative feedback effect on ACTH?

Cortisol

11

What hormones have a negative feedback effection LH and FSH?

Testosterone
Oestrogens

12

What regulates cholesterol import into the mitochondria?

LH in gonads
ACTH in adrenal cortex

13

What imports cholesterol into cells?

LDL receptor

14

What imports cholesterol into mitochondria?

Steroidogenic acute regulatory protein (StAR)

15

What is the acute effect of LH on cholesterol transport?

Formation of cAMP and PKA
PKA phosphorylates and activates StAR

16

What is the chronic effect of LH on cholesterol transport?

Gene transcription of steroidogenic enzymes; eg: StAR

17

What are the two endocrine glands of the adrenal glands?

Cortex
Medulla

18

What are the three regions of the adrenal cortex?

Zona glomerulosa
Zona fasciculata
Zona reticularis

19

What regulates the zona glomerulosa?

Renin-angiotension

20

What does the zona glomerulosa secrete?

Minerolcorticoids: aldosterone

21

What regulates the zona fasciculata?

ACTH

22

What does the zona fasciculata secrete?

Glucocorticoids: cortisol

23

What regulates the zona reticularis?

ACTH

24

What does the zona reticularis secrete?

Androgens

25

What regulates the adrenal medulla?

Sympathetic nervous system

26

What does the adrenal medulla secrete?

Adrenaline
Noradrenaline

27

How much testosterone is produced by the zona reticularis?

Limited because of low enzyme expression under physiological conditions

28

What does a deficiency in aldosterone synthase cause?

No aldosterone
Aberrant formation of other hormones

29

What is the two cell model of follicular biosynthesis of oestrogen in the ovaries?

Theca cells stimulated by LH
Make progesterone and androstenedione from cholesterol
Thecal cells secrete androstenedione
Granulosa cells take up androstenedione
FSH stimulates increased expression of aromatase in granulosa cells only
Androstenedione converted to estradiol

30

Which enzyme is responsible for converting androstenedione into testosterone in the testes?

17 beta-hydroxysteroid hormone dehydrogenase 3 (17beta-HSD 3)