Human Reproduction System

[Asanii]

HI,
I am having trouble with a question in one of my lessons, the question is...

Explain why it is necessary that estrogen and progesterone inhibit the secretion of FSH and LH

I know that high levels of Estrogen/Progesterone suppress the release of GnRH providing a negative feedback control of hormone levels, to suppress further production of FSH and LH but why do they inhibit the secretion of FSH and LH?

Any help would be greatly appreciated.

Asanii

[mande]

FSH stimulates the development of follicles while LH stimulates the remaining follicle to develop into the corpus luteum and also for ovulation to occur.

The negative feedback mechanism whereby the secretion of FSH and LH is halted occurs because the estrogen and progesterone now move in to stimulate the uterine wall to become progressively thicker thus the need for the development of any more follicles is unnecessary.

Both oestrogen and progesterone alone signals the hypothalamus and the pituitary gland to stop further secretion of FSH and LH hence the levels of both FSH and LH would dramatically fall and finally plateau after the 14th day.