Vitamin D and steroids (19) Flashcards
(44 cards)
What is cholesterol the precursor for?
- glucocorticoids - cortisol
- mineralcorticoides - aldosterone
- sex hormones - androgens, estrogens, progestins
Where is the receptor for a steroid ?
cytoplasm or nucleus
What is the rate limiting step in steroid synthesis?
conversion of cholesterol to 21 C pregenolone
-cyt P450SCC or desmolase
Where is p450 SCC located?
on the inner mitochondrial membrane
What protein mediates the movement of cholesterol from the outer mito membrane to the inner?
StAR
What happens when there is a defect of 3-B-hydroxysteroid dehydrogenase?
-build up of pregnenolone
-no synthesis of any steroids:
glucocorticoids
mineralcorticoids
androgens
estrogens
- female like genitalia
What happens if there is a defect in 17-alpha-hydroxylase?
- build up of progesterone
- no sex hormones or cortisol
-inc production of mineralcorticoids
Na+ fluid retention –> HTN
-female like genitalia
What happens if there is a 21-alpha-hydroxylase deficiency?
-no synthesis of: minercorticoids & glucocorticoids
overproduction of androgens:
masculization of external genitalia in females
early virilization in males
What happens in a 11-B hydroxylase defiency?
decrease in cortisol, aldosterone, corticosterone
fluid retention
overproduction of androgens
What deficiency is the most common?
21-alpha-hydroxylase
Where is cortisol produced?
zona fasiculata of the adrenal cortex
Describe the pathway leading to the release of cortisol?
- CRH by hypothalamus in response to stress
- anterior pituitar releases ACTH
- cortisol secreted by adrenal cortex
How does ACTH lead to production of cortisol?
- G protein receptor - inc cAMP, activated PKA
- activation of lipase
- converts cholesterol esters to cholesterol - activation of StAR
- cholesterol moves to inner mit membrane - cholesterol–> pregnenolone
- moves to cytosol - pregnenolone –> progesterone
- progesterone –> 11 -deoxycortisol
- 11-deoxycortisol –> cortisol
Which enzymes catalyze the conversion of progesterone –> 11-deoxycortisol?
CYP17, CYP21
Which enzyme catalyzes the B-hydroxylation at C21 of 11-deoxycortisol to convert it to cortisol?
CYP11B1
Where is aldosterone produced?
outer layer of the adrenal cortex: zona glomerulosa
What stimulates the production of aldosterone?
decrease in plasma Na+/K+
angiotensin II
What converts angiotensinogen to angiotensin I?
Renin secreted by kidneys
What converts angio I –> angio II?
ACE
What are ACE inhibitors used to treat?
renin dependent BP
What are androgens produced by?
inner and middle layers of adrenal cortex
zona reticularis
What stimulates the release of LH and FSH from the anterior pituitary?
GRH from the hypothalamus
What is the function of LH?
causes testes to produce testoerone, ovaries to produce estrogen and progesterone
What is the function of FSH?
regulates growth of ovarian follicles
regulates spermatogenesis
