w5 - reproduction/sex steroid axis: physiology ad biochem Flashcards
6 key repro hormones
GnRH LH FSH Oestrogen Progesterone Testosterone
effect of FSH in 1) males, 2) females
1 - testes do spermatogenesis
2- growth of ovarian follicles (oogenesis), causes ovary to secrete oestrogen
effect of LH in 1) males, 2) fema
1 - testes secrete testosterone
2- causes ovulation, progesterone producion (by corpus luteum)
what is responible for the release of FSH and LH (from ant. pit)
Gonadotrophin releasing Hormone (GnRH)
GnRH comes from
hypothalamus
hypothalamus - pit - gonadal axis
GnRH is secreted constantly in females, but pulsatile in males t.f
false
males - constant pulsatile manner
females - freq. varies during menstrual cycle
High-frequency GnRH pulses stimulate __ pulses whereas low-frequency pulses are required for ___ release
LH
FSH
conc of what will incr GnRH pulsatility, driving release of LH
oestrogen
incr in ___ conc reduces the freq of GnRH pulses
progesterone
onset og puberty maturation is assoc with a steady acceleration in __ ___
GnRH pulsatility
activation of GnRH pulse frequency is a central mechanism associated with delayed puberty, what/when to consider for boys/girls
females: no period by age 15
males: no testicular development by age 14
other than progesterone and oestrogen, what else regulates GnRH pulsatility
kisspeptin
menstrual cycle, when is LH/progesterone/FSH/estradiol at their highest
LH + FSH + Estradiol all just before ovulation
Progest - during LH
FSH stimulates growth of ___ ___(associated with an increase in oestrogen levels)
Rising oestrogen levels in turn exert negative feedback regulation (level of hypothalamus and pituitary) to lower ___ (temporarily)
Once oestrogen reaches a certain concentration it exerts positive feedback regulation resulting in an increase in ___ and the LH ‘surge’
LH surge eventually leads to ____ and regulates the formation of the ___ ___ and progesterone production and secretion
Increasing progesterone decrease LH secretion by influencing __ __
ovarian follicles
FSH
FSH
ovulation
corpus luteum
GnRH pulsatility
Endometrium thickens under the influence of ___ and a becomes a secretory tissue under the influence of ___
oestrogen
progesterone
a follicle consists of an oocyte surrounded by folliciular cells (granulosa and theca cells) explain what happens during Follicular phase
incr in follicular cells
accumulation of follicular fluid
LH surge precedes ovulation by approx.
34-36hrs
how does LH surge come about
oestrogen rises >200pg/ml, increases GnRH pulsatility which causes LH surg
formation of corpus luteum occurs due to transformation of oocytes to luteal cells t.f
false
follicular cells - theca + granulosa
LH stimulates angiogenesis which ensures efficient delivery of cholesterol, why is this important
cholesterol i a substrate for prog. synthesis
LH also stimulates enzymes involved in this conversion
functiion of oestrogen
Increase the thickness of the vaginal wall
Regulate the LH surge
Reduce vaginal pH through increase in lactic acid production
Decrease viscosity of cervical mucus to facilitate sperm penetration
function of progesterone
progesterone = pro gestation
endo wall thickness maintained
relaxes myometrium,
testosterone is synthesised from ___, due to LH binding to receptos on __ cells
cholesterol
LEydig
testosterone stimulates spermatogenesis through which cells
Sertoli cells
in testes, which cell expresses the FSH receptor
sertoli cells
FSH stimualtes prodution of ABP (androgen binding proein) by sertoli cells
