02 Roles of Hormones in the Menstrual Cycle

1. Hormonal control of gametogenesisHormonal control of gametogenesis
•Control centre – Control centre – hypothalamushypothalamus and and
pituitary glandpituitary gland (act as controlling link (act as controlling link
between the nervous system and the between the nervous system and the
endocrine system)endocrine system)
•Pituitary gland:Pituitary gland:
–2 2 gonadotrophic hormonesgonadotrophic hormones
•stimulate gonadsstimulate gonads
•secreted in response to secreted in response to gonadotrophin gonadotrophin
releasing hormonereleasing hormone ( (GnRHGnRH))
–follicle stimulating hormonefollicle stimulating hormone ( (FSHFSH))
–luteinising hormoneluteinising hormone ( (LHLH))
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3. Menstrual cycle and hormonal Menstrual cycle and hormonal
control of oogenesiscontrol of oogenesis
•In the female, gametes and sex hormones In the female, gametes and sex hormones
production is cyclic (production is cyclic (menstrual cyclemenstrual cycle))
•The first day of the cycle is counted from The first day of the cycle is counted from
the start of the start of menstruationmenstruation (shedding of (shedding of
the bloody lining of the uterus the bloody lining of the uterus
(endometrium) through the vagina)(endometrium) through the vagina)
•2 halves:2 halves:
–Egg is producedEgg is produced
–Uterus is prepared for implantation in case the Uterus is prepared for implantation in case the
egg is fertilisedegg is fertilised
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5. •Anterior lobe (pituitary gland) – FSH in blood – Anterior lobe (pituitary gland) – FSH in blood – ovaryovary – stimulates – stimulates
development of a primary follicledevelopment of a primary follicle
•Maturing follicle – oestrogen in blood – Maturing follicle – oestrogen in blood – uterus and anterior lobe uterus and anterior lobe
(pituitary gland)(pituitary gland) – stimulates repair and thickening of – stimulates repair and thickening of
endometrium (uterus)/inhibits secretion of FSH and LH (anterior endometrium (uterus)/inhibits secretion of FSH and LH (anterior
lobe) except when increased greatlylobe) except when increased greatly
•LH – ovary – causes LH – ovary – causes ovulationovulation; stimulates the remains of Graafian ; stimulates the remains of Graafian
follicle to develop into the corpus luteum; stimulates secretion of follicle to develop into the corpus luteum; stimulates secretion of
progesterone; reduces oestrogen production, which in turn reduces progesterone; reduces oestrogen production, which in turn reduces
FSH and LHFSH and LH
•Corpus luteum – progesterone and oestrogen – Corpus luteum – progesterone and oestrogen – uterus and uterus and
anterior lobe (pituitary gland)anterior lobe (pituitary gland) – stimulates glandular activity in – stimulates glandular activity in
endometrium; helps oestrogen in maintaining thickness of endometrium; helps oestrogen in maintaining thickness of
uterus/enhance the negative feedback effects of oestrogen and uterus/enhance the negative feedback effects of oestrogen and
inhibit FSH and LH secretion (anterior lobe)inhibit FSH and LH secretion (anterior lobe)
–Absence of FSH – no second eggAbsence of FSH – no second egg
–Progesterone – temperature rise in female bodyProgesterone – temperature rise in female body
•If pregnant, corpus luteum receives hormone stimulus from If pregnant, corpus luteum receives hormone stimulus from
implanted embryo (if not it degenerates)implanted embryo (if not it degenerates)
–As it degenerates, supply of oestrogen and and progesterone is cut offAs it degenerates, supply of oestrogen and and progesterone is cut off
–FSH no longer inhibited and switched on (completing cycle)FSH no longer inhibited and switched on (completing cycle)
–Lining of uterus breaks down (menstruation)Lining of uterus breaks down (menstruation)
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