Biochem Seminar 1 Flashcards
(10 cards)
When does DHEA levels reach its peak?
25-30 years of age
It’s high at childbirth but decreases gradually and stays low throughout childhood. But increases again at puberty and levels peak at 25-30 years of age, then it gradually decreases until it reaches 0 (adrenopause)
What is the reason that in the fetus there is shuttling of pregnenolone P5 to DHEA instead of progesterone?
Lack of 3B-HSD in the fetus
Cholesterol
|
Pregnenolone P5 —> 17-hydroxy pregnenolone —> DHEA
|x3BHSD |x3BHSD |x3BHSD
Progesterone 17-hydroxyprogesterone Androstrenedione
Can the fetal adrenal cortex produce cortisol?
Yes. It can’t convert P5 (pregnenolone) to P4 (progesterone) bc it lacks 3B-HSD. BUT the placenta has 3B-HSD and it provides the fetal adrenal cortex with P4 to produce cortisol for fetal growth.
This ensures that the fetus has its needed DHEA, and it gets what it requires of cortisol which isn’t a lot it could be harmful if too much
What is the primary site of estrogen production during pregnancy?
Placenta
What is the purpose of knowing a pregnant woman’s E3 level?
Monitor pregnancy health
What enzyme gives estriol after aromatase?
16a-hydroxylase
What converts estrone into estradiol and vice versa?
17b-hydroxysteroid DH
Why can’t CYP19 or aromatase affect DHEA?
Bc it doesn’t have a keto group with an adjacent acidic H
What are the 2 enzymes that DHEA specifically regulates the expression of?
1) DDSP= DHEA-induced specific dual phosphatase (prevents obesity)
2) 11b-HSD= inc. cortisol
What are the possible mechanisms for adrenopause?
• A decrease in CYP17 (17, 20 lyase) activity, the enzyme
that catalyzes 17-OH-P5 à DHEA
• Accumulation of lipid peroxidation products (lipofuscin) in
the adrenal zona reticularis (ZR) where DHEA is
produced
• Atrophy of the adrenal ZR with age
