Flashcards in Steroid Hormones Deck (54)
What is the precursor for steroid hormones?
What happens to cholesterol during steroid hormone synthesis?
C atoms undergo redox reactions
To what are cytochrome P450 enzymes bound within the cell?
Mitochondrial/endoplasmic reticulum membranes
What do cytochrome P450 enzymes contain?
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
What happens in the first step of steroid hormone biosynthesis?
Cholesterol side chain cleavage enzyme (cholestero SCC) converts cholesterol > pregnenolone
What is the first intermediate of steroid hormone synthesis?
What do hydroxysteroid dehydrogenases (HSD) do?
Catalyse interconversion of C-OH to C=O
Reduction reaction using NADH
What are the major pituitary hormones regulating steroid hormone synthesis?
What hormone has a negative feedback effect on ACTH?
What hormones have a negative feedback effection LH and FSH?
What regulates cholesterol import into the mitochondria?
LH in gonads
ACTH in adrenal cortex
What imports cholesterol into cells?
What imports cholesterol into mitochondria?
Steroidogenic acute regulatory protein (StAR)
What is the acute effect of LH on cholesterol transport?
Formation of cAMP and PKA
PKA phosphorylates and activates StAR
What is the chronic effect of LH on cholesterol transport?
Gene transcription of steroidogenic enzymes; eg: StAR
What are the two endocrine glands of the adrenal glands?
What are the three regions of the adrenal cortex?
What regulates the zona glomerulosa?
What does the zona glomerulosa secrete?
What regulates the zona fasciculata?
What does the zona fasciculata secrete?
What regulates the zona reticularis?
What does the zona reticularis secrete?
What regulates the adrenal medulla?
Sympathetic nervous system
What does the adrenal medulla secrete?
How much testosterone is produced by the zona reticularis?
Limited because of low enzyme expression under physiological conditions
What does a deficiency in aldosterone synthase cause?
Aberrant formation of other hormones
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