2.1 HPG axis lecture: females

Question 1

where do FSH and LH primarily act on in females? via?

Answer 1

on gonads
via Gas (G alpha s) - GPCR
PCR –> adenylate cyclase (secondary messenger)

Question 2

what are the target cells of FSH and LH in females?

Answer 2

ovarian granulosa cells

theca interna

Question 3

what is the function of FSH and LH in females?

Answer 3

1. stimulate sex hormone synthesis (steroidgenesis) e.g. oestrogen, progesterone, inhibin
2. control gamete production (folliculogenesis and ovulation)

Question 4

what is the effect of low (moderate) titres of oestrogen on GnRH secretion?

Answer 4

reduces GnRH secretion - negative feedback

Question 5

what is the effect of high titres of oestrogen ALONE on GnRH?

Answer 5

promote GnRH secretion:
positive feedback
cause LH ‘surge’ –> ovulation

Question 6

function of progesterone?

Answer 6

1. increases inhibitory effects of moderate oestrogen
2. prevents positive feedback of HIGH oestrogen (no LH surge) - corpus luteum
3. increases frequency of GnRH pulses (pulse more often)

Question 7

oestrogen effects on GnRH pulse?

Answer 7

reduces GnRH PER pulse (amount per pulse)

Question 8

effect of inhibin on FSH?

Answer 8

inhibits the secretion of FSH (same as male)

has SMALL inhibitory effect on LH

Question 9

where is inhibin released from?

Answer 9

granulosa cells of corpus luteum

from ova: follicle –> corpus luteum