Explain how FHS and oestrogen illustrate the principle of negative feedback during the menstrual cycle, and explain therefore why oestrogen may be used as a contraceptive.

FHS is released from the anterior pituitary gland in the brain and causes the follicle to develop in the ovary. the developing follicle produces and secretes oestrogen. This release of oestrogen stimulates the release of LH - also from the anterior pituitary gland, stimulates the growth and repair of the endometrium for implantation, and inhibits the further release of FHS (this is to ensure that only one follicle develops). This is an example of negative feedback as the release of FHS has eventually lead to the inhibition of this hormone by oestrogen. oestrogen can be used as a contraceptive as it inhibits the release of FHS from the anterior pituitary gland, therefore no follicles will develop in the ovaries. This prevents the entire process from occurring meaning that no oocyte can be fertilised by sperm, removing the females ability to fall pregnant - suitable for a contraceptive.