steroid biosynthesis Flashcards
is endocrine signaling long or short lasting
long lasting
lypophilic signaling molecules: steroid hormones
steroid hormones: progesterone, estradiol, testosterone, vitamin D, aldosterone, cortisol
(PET VAC)
lipophilic hormones 3 classes
steroid hormones
thyroid hormones
retinoids
lipophilic signal molecules: thyroid hormones
thyroxine
lipophilic signal molecules retinoids
retinol, retinoic acid
3 parts of intracellular receptors
DNA binding domain, ligand-binding domain, and txn-activating domain
what are steroid hormones synthesized from ___ in ___ and where
cholesterol in the smooth ER of adrenal cortex, ovaries, and testes
where do adrenal cortex, ovaries, and testis get cholesterol from
circulating LDL
de novo synthesis from acetyl coA
from cholesterol esters stored in cytoplasmic lipid droplets
acetyl coA pathway with steroids
acetyl coA X 3 = IPP
IPP can form
steroids, lipid soluble vitamins, ubiquinone, heme tails
how many IPPs do you need to make vitamin D
-how many carbons is it
6 unit, 27 carbons
what is the RL step of steroid hormone synthesis
cholesterol to pregnenolone
desmolase is enzyme used
what is a stimulator of desmolase
ACTH activates expression
LH increases activity
pregnenolone effects without conversion
- works as modulator of NT signaling in brain
- effects NMDA gluatamte receptor (memory and learning)
glucocorticoids have affinity for ___ receptors and are 100 times more concentrated
mineralcorticoid
what must pregnenolone be converted to to make other progestrogens and what enzymes are responsible
progesterone
-17a hydroxlase and 3-B hydroxysteroid dehydrogenase
progesterone is specifically converted in a tissue specif manner to
aldosterone, cortisol, estradiol and testosterone
estradiol comes from where
testosterone in ovaries, minor amt in adrenal cortex
what is formed along with testosterone in the testes and is more potent
dihydrotestosterone
conversion of testosterone to estradiol enzyme and stimulatory factor
testosterone —-aromatase—> estradiol
-occurs in ovaries, FSH is positive stimulator
where is desmolase found
only in tissues that produce steroid hormones
gonads, and adrenal cortex
21-hydroxylase deficiency
hyponatremia, hypoglycemia
-in females causes virilism (development of male secondary characterisitcs)
if have a deficiency of 17-a hydroxylase this causes what?
can be compensated by what
loss of cortisol and sex steroids
-decrease in cortisol is compensated by increased production of corticosterone (aldosterone arm)
defect in 11-B hyrdroxylase
causes hypertension due to accumulation of 11-decoxycorticosterone which has mineralcorticoid like effects
how does cortisol suppress immune system
induce production of i-kBa which helps keep NF-kB inactive in cytoplasm
- NF-kB is required for cytokines like IL-2 needed for T cell prolif
- Cortisol promotes T cell apoptosis
- decreased IL-2 and its receptor lead to inhibtion of clonal expansion of B lymphocytes as well
