L20 Sex Hormones And Oral Contreceptives Flashcards
(30 cards)
How does oestrogen affect fertility?
- growth of ovarian follicles
- endometrial growth
- increase in tubal motility and uterine contractions
How does oestrogen influence lactation?
- stimulation of duct growth
- inhibited milk let-down (prolactin)
What are the secondary sexual characteristics determined by oestrogen?
- breast development
- female habitus (skeletal, skin, metabolism)
- development of external genitalia
How does progesterone influence fertility?
- endometrial receptivity
- decrease in fallopian tube motility
- decrease in uterine contractions
How does progesterone influence lactation?
- stimulation of lobuloalveolar development
- inhibits milk let down (prolactin)
Where is the GnRH pulsatile generator?
In the arcuate nucleus of the hypothalamus
Where is GnRH released?
Released into the bloodstream
Travels to the anterior pituitary gland
What does the anterior pituitary release?
FSH - follicle stimulating hormone
LH - leutining hormone
Where do FSH and LH bind and what do they release?
Bind receptors on different target cells in the ovary
FSH - releases oestrogen
LH - releases progesterone
What is the role of oestrogen in the hypothalamic-pituitary-ovarian axis?
- follicular egg maturation
- proliferation of endometrium
- inhibits FSH so regulates the cycle
What is the role of progesterone in the hypothalamic-pituitary-ovarian axis?
- renders the endometrium suitable for implanting of a fertilised ovum
- inhibits further release of GnRH, FSH and LH so regulates the cycle and ovulation
Describe the follicular phase of the ovarian cycle
1) FSH is increasing due to low ovarian hormone production
2) FSH aids follicular development
3) follicles produce oestrogen
4) high concentration of oestrogen for more then 48 hours
What happens during the ovulation phase?
1) positive feedback from increased oestrogen initiates the LH surge
2) the LH surge induces ovulation
3) the remainder of the ovulatory follicle becomes luteinised (CL formation)
4) it secretes progesterone and oestrogen (CL in bloom)
5) if not pregnant then CL regresses and there is a decrease in progesterone and oestrogen
What happens after ovulation if no fertilisation takes place?
1) endometrium can not be maintained so menstruation occurs
2) lack of progesterone also means the clamp on GRH, FSH and LH secretion is released
3) these hormones are secreted again and the cycle starts again and follicles develop
Why do progesterone and oestrogen levels drop when there’s non fertilisation?
Due to corpus luteum regression
What happens after ovulation if fertilisation takes place?
1) maintains endometrium and pregnancy
2) thicken cervical mucus
3) inhibits further secretion of GRH, FSH and LH which prevents further follicles developing
What does the ovum secrete when fertilisation takes place?
Secretes human chorionic gonadotrophin (HCG)
- this stimulates corpus luteum to continue secreting progesterone
What’s required to induce follicle formation and ovulation?
GnRH
FSH
LH
They are ER and PR agonists
What are oestrogen and progesterone required for?
Required to feedback on hypothalamus and pituitary and so inhibit further follicles being formed
- ER and PR agonists
What maintains pregnancy?
Progesterone
- PR antagonist
What do oral contraceptives target?
Target the negative feedback system which clamps the secretion of GRH, FH and LH
What is eostrogens role in the combination pill?
Eostrogen inhibits the secretion of FSH via the negative feedback loop
- prevents the development of ovarian follicles
- blocks ovulation by blocking the FSH peak
What is progesterones role in the combination pill?
Inhibits the secretion of LH
- prevents ovulation by blocking the LH surge
- makes the cervical mucus less suitable for the passage of sperm
How long is the combo pill taken for?
21 days
Then a 7 pill free period (causes withdrawal bleeding)
