gonadal axis Flashcards
where is GnHR released from
hypothalamus
how is GnHR released
in a pusaltile manner
what does GnRH act on
the anterior pituitary
what does the anterior pituitary produce
LH
FSH
what causes FSH to be produced
Low frequency GnHR
what causes LH to be produced
High frequency GnHR
what does LH act on
testes
ovaries
what does FSH act on
testes
ovaries
what affect does FSH have on the testes
causes the testes to produce sperm (spermatogenesis)
what does inhibin act on
FSH
what affect does inhibin have on FSH
it inhibits its production to decrease FSH secretion
what affect does LH have on the testes
causes the testes to produce testosterone
how is GnHR released in males
at a constant rate
what cassette release of testosterone
LH from the anterior pituitary
what happens to the testosterone that is released
90% is taken up by sertoli cells the rest is free within the blood
where are sertoli cells located
seminiferous tubules
what does high levels of testosterone do
decreases GnRH causing a drop in LH
what is the role of testosterone
maintains the testes-blood barrier
controls release of mature sperm from sertoli cells
how long does spermatogenesis take
70 days
what causes the release of GnHR, what are the receptors involved
FSH & LH
kisspeptide receptors
how is LH released in females
released as a surge in response to high frequency GnHR
what does LH cause in females
ovulation
formation of the corpus lutem which will produce and secrete progesterone
what is the corpus lutem made of, when does it form
granulosa and theca cells which transform into luteal cells
forms after ovulation
when does the LH surge occur
34-36hrs before ovulation
when is FSH released in females
in response to low frequency GnHR
what does FSH cause in females
growth of follicles
causes the ovary to secret oestrogen
where is progesterone secreted from
corpus lutem
what does progesterone do
pro-gestation (maintains pregnancy)
maintains endometrial thickness
relaxes myometrium
causes thick/infertile mucus
what does do high levels of progesterone do
decreases GnHR causing a decreased LH
when do progesterone levels peak
AFTER ovulation
what produces oestrogen
ovaries, placenta an adrenals
what does oestrogen do
thickens endometrium
reduces vaginal pH via lactic acid
decrease mucous viscosity
regulates LH surge
how is the LH surge regulated
high levels of oestrogen causes increased GnHR which results in increased levels of LH
when does oestrogen levels peak
BEFORE ovulation
how long is a typical menstrual cycle
28-35 days
what are the two phases of the menstrual cycle, when do they occur
before ovulation = follicular phase
after ovulation= luteal phase
how long does the follicular phase last
typically 14 days +/- 7
very variable
what is the follicular phase characterised by
follicular growth
how long does the luteal phase last
14 days (very constant)
what causes the formation of the corpus lutem
LH