Flashcards in Steroid Hormones Deck (54)
Loading flashcards...
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
