Male endocrine Flashcards
2 main cell types in seminiferous tubule
- leydig
2. sertoli
what does leydig cell produce and respond to
produce: T
responds to: LH
what does sertoli produce and respond to?
produce: and. binding homrone, inhibin, fluid, mullarian inhib. factor
responds to: FSH
what stimulates FSH/LH and how
GnRH in pulsatile fashion
what inhibits FSH/LH
T and inhibin
how often does GnRh pulse
every 2-3 hours
where does T feedback to and in what direction?
- GnRH -ve
2. LH -ve
what are T levels in testes and rest of body
testes - 100-600ng/ml
body 2/5-10 ng/ml
what type of hormones are T and Est
steroid
what are all steroid hormones derived from
cholesterol
what is path from cholesterol to estrane and what are they converted to?
cholesterol>pregnane (progesteron)>androstane(androgens)>estrane(estrogens)
what is path from cholesterol to pregnenolone
cholesterol side chain cleavage enzyme
what is path from pregnenolone to androstendione
pronenolone(hydroxysteroi dehydrogenase)>progesterone(17a-hydroylase)>10-OH-progesterone(17,20 lyase)>androstenedione
path from pregnenolone to DHEA
pregnenolone(17a-hydroxylase)>17-OH-preg(17,20-lyase)> DHEA
of these 2 which is prominent
DHEA
what is product f DHEA and androstendione and how
testosterone vis 17B-hydroxysteroid dehydrogenase
what are 2 products of Test and via what enzyme
- hihydrotestosterone (5a-reductase)
2. estradiol (CYP19 aromatase)
how are most adrogens bound
sex hormone binding globulin>albumin>free
when are 3 peaks of T in men
- fetal - differentiation
- neo-natal - ??
- puberty on - reproduction
where is T located in the body and how much
95% testes
5% peripheral
what are 2 types of %a-reductase and where
type 1 - skin, body, scalp
type 2 - genitals + prostate
what causes BPH
DHT via type 2
what can be given as an inhibitor
finasteride - antagonist to type 2 5a-reductase
which is more stable DHT or T
DHT
how do DHT and T bind differently
DHT binds to same receptor but works on nuleas
what is T responsible for in terms of phenotype
- muscle mass
- sex drive
- GnRH
4 spermatogenis - sexual differentiation
- wolffian stimulation
what is DHT responsible for in terms of phenotype
- external virilization
2. sexual maturation at puberty
what happens if we give continuous GnRh analogues
kills LH and FSH levels - slow precocious puberty and prostate cancer
what would systemic injections of T do to sperm production
drop it
