Steroid Endocrinology Flashcards
where is GnRH made? where is it released and what does it do?
GnRH is made in the hypothalamus
it is released into the anterior pituitary where it stimulates the secretion of LH and FSH (gonadotropins)
describe pulsatile release
GnRH secretion is pulsatile because continual expression is ineffective in the release of gonadotropins
what is kisspeptin and why is it important
kisspeptin is within presynaptic neurons which generate the GnRH pulses
kisspeptin is pulsatile and everything downstream of it is pulsatile as well
subunits of gonadotropins: alpha versus beta
the alpha subunit is the same in gonadotropins, but the beta subunit is unique to each hormone
what does FSH do in females
FSH binds to granulosa cells, promotes follicular development and promotes the differentiation of theca cells
what does FSH do in males
FSH binds to Sertoli cells and is required for the completion of meiosis
what does LH do in females
in females, LH binds to theca cells and the LH surge promotes ovulation
what does LH do in males
in males, LH binds to leydig cells and stimulates testosterone production
what is hCG
hCG is a pregnancy hormone in the placenta
what produces estrogens in females
estrogens are produced by granulosa cells
what does estrogen do in females
develops female secondary characteristics, prepares the reproductive tract for sperm, and increases progesterone receptors in the uterus
what produces estrogen in males
Sertoli cells produce estrogen
what does estrogen do in males
inhibits spermatogenesis
what produces progesterone in females
luteal cells and placenta
what does progesterone do in females
promotes gestation
what produces progesterone in males
leydig cells
what does progesterone do in males
secondary sex characteristics, inhibits LH and FSH for negative feedback, essential for spermatogenesis and sperm maturation
significance of dihydrotestosterone
it is produced in sertoli cells from testosterone via 5 alpha reductase
it is the most potent androgen and gives rise to external genetalia
what do inhibin, activin, and follistatin do
inhibin suppresses FSH
activin promotes FSH
follistatin suppresses FSH
significance of dimers in activin and inhibin
activin and inhibin are dimers, however the alpha subunit in inhibin is inhibitory. if it was knocked out, it would no longer be inhibitory
what do PGF2 and PGE2 (prostaglandins) do?
PGF2: promotes luteolysis in the ovary
PGE2: promotes cervical ripening prior to parturition
where is melatonin produced and what is its significance
melatonin is produces in the pineal gland and it is dependent on daylight (higher levels in the winter)
describe negative feedback of GnRH
testosterone is made when LH binds to sertoli cells. testosterone negatively regulates GnRH
inhibin is made by sertoli cells when bound to FSH. inhibin negatively regulates FSH
what happens to gonadotropins after castration or spay
LH and FSH levels become high because inhibin and testosterone are not being produced, so there is no negative feedback
