Hormone Action IV Flashcards
1
Q
what are the “steriodogenic” tissues in the body?
what steroids do they produce?
A
- adrenal cortex
- zona glomerulosa - aldosterone
- zona fasculata & reticularis - glucocorticoid (cortisol)
- zona reticularis - andogens (DHEA, andorstenedione)
- testis
- testosterone
- ovary
- estrogens (estradiol, estriol, estrone)
- progesterone
2
Q
what do all steroids have in common?
A
- derived from cholesterol
- contain cyclopentanophenanthrene ring
3
Q
how many carbons are in cholesterol?
what about cortisol, testosterone and estrogen
A
- cholesterol - 27 C
- cortisol - 21 C
- testosterone - 19 C
- estrogen - 18 C
4
Q
in what organelle does steroid synthesis occur?
why is this important?
A
in the mitochondria
- this is impt because it requires that STAR (steroidogenic acute regulatory protein) transports cholesterol from the plasma the mitochondira
5
Q
the rate limiting step of steroid hormone synthesis?
- is done by what enzyme?
- requires what cofactors?
- occurs where?
A
-
cholesterol side chain cleaveage (irreversible)
- cleavage of cholesterol (27 C) to a 21 C molecule + 6 C molecule
- 21 C molecule = pregnelone
- 6 C molecule = isocaproaldehyde
- by: cholesterol-20,22 desmolase
- ACTH-dependent esterase
- in mitochondria (of steriogenic tissues)
- cleavage of cholesterol (27 C) to a 21 C molecule + 6 C molecule
6
Q
after pregnenolone + isocaproaldehyde are formed, where are they further processed to yield steroid hormones?
A
in the smooth ER
7
Q
mineralcorticoid synthesis
- occurs where?
- depends on what critical enzymes?
- has what roles in the body?
A
aka aldosterone
- in the zona glomerulosa (of the adrenal cortex)
- depends on:
- 3B-hydroxysteroid dehydrogenase
- 12-hydroxylase
- 11B-hydroxylase
-
18-hydroxylase & 18-hydroxydehydrogenase (aldosterone synthase) = aldsterone synthase
- ONLY present in zona glomerulosa.
- inc Na / dec K+
8
Q
glucocorticoid synthesis
- occurs where?
- depends on what enzymes?
- has what role in the body?
A
= cortisol
- mostlhy in zona fasculata (spongiocytes) of adrenal cortex;
- depends on 17a-hydroxylase, part of P450c17 protein
- serve to
- regulate carbohydrate / FA metabolism
- immunosuppress
9
Q
androgen synthesis
- occurs where?
- relies on what key enzymes?
- produeces what steroids?
- that have what biologic effects?
A
- in zone reticularis of adrenal cortex
- depends on 17, 20 lyase (17,120 desmolase), part of P450c17 protein
- produces:
- DHEA > androstenedione
- yield to testosterone –> estrogen = sex effects
- DHEA > androstenedione
10
Q
testosterone synthesis
- occurs where?
- under what regulation?
- depends on what enzymes?
- has what rate limiting step?
- has what effects?
A
- in leydig cells (in the testicular interstitium)
- under regulation of LH (from GnRH)
- synthesis:
- unique enzyme: 17B-hydroxysteroid hydrogenase: androgens –> testosterone
- thus, depends on 17,20-lyase
- rate limiting step: STAR (moves cholesterol into mitochondria)
- unique enzyme: 17B-hydroxysteroid hydrogenase: androgens –> testosterone
- roles: secondary sex characteritics
11
Q
dihydrotestosterone (DHT)?
- is produced where?
- how?
- has what significance?
A
- formed in peipheral tissues (ex: prostate) - not in the testes,
- from testosterone - by 5a-hydroxylase
- more potent than testosterone
12
Q
adrogen binding protein
- produced where?
- under what regulation?
- has what role?
A
- by sertolie cells in seminferous epitheium
- under regulation of
- FSH (from GnRH)
- testosterone (+)
- secreted into tubular lumen to bind & maintain high levels of testosterone
13
Q
summarize the roles of LH and FSH in the male.
A
- hypothalamus produces GnRH
- GnRH –> acidophiles (ant pituitary)
- LH –> leydig cells
- testosterone
- secondary sex characteristics
- sertoli cells
- ABP
- testosterone
- FSH –> sertoli cells
- spermatogenesis:
- synthesis of:
- ABP
- inhibin - inhibits FSH
- LH –> leydig cells
- GnRH –> acidophiles (ant pituitary)
14
Q
how is negative feedback exerted in the male reproductive cascade?
A
by
-
testosterone (from LH) inhibits production of LH
- @ hypothalamus & ant pit
-
inhibin (from FSH) inhibits production of FSH
- @ ant pit
15
Q
estrogen synthesis?
- occurs where?
- under what regulation?
- depends on what enzyme?
- produces what products?
- that have what effects?
A
main estrogen = 17B-estradiol
- occurs in
- ovarian follicles: directly from testosterone
- peripheral tissues: from other androgens (androstenedione)
- depends on: aromatase
- under regulation: of FSH (from GnRH)
- effects:
- female secondary sex characteristics (breasts, fat deposition, high pitched voice)
- does aslso exist in males
- female secondary sex characteristics (breasts, fat deposition, high pitched voice)
18
Q
discuss the two major phases of the menstrual cycle and
- what hormonal fluctuations they involve
- what key events they include
- how they effect the uterine lining
A
two major phases
- follicular phase
- triggered by FSH,
- acts on follicular cells to induce
- follicular proliferation
- rise in estrogen
- endometrium grows
- luteal phase
- triggered by LH, which
- act on corpus luteam to induce
- ovulation
- rise in progesterone
- endometrium grows
