L20 Sex Hormones And Oral Contreceptives

Question 1

How does oestrogen affect fertility?

Answer 1

• growth of ovarian follicles
• endometrial growth
• increase in tubal motility and uterine contractions

Question 2

How does oestrogen influence lactation?

Answer 2

• stimulation of duct growth
• inhibited milk let-down (prolactin)

Question 3

What are the secondary sexual characteristics determined by oestrogen?

Answer 3

• breast development
• female habitus (skeletal, skin, metabolism)
• development of external genitalia

Question 4

How does progesterone influence fertility?

Answer 4

• endometrial receptivity
• decrease in fallopian tube motility
• decrease in uterine contractions

Question 5

How does progesterone influence lactation?

Answer 5

• stimulation of lobuloalveolar development
• inhibits milk let down (prolactin)

Question 6

Where is the GnRH pulsatile generator?

Answer 6

In the arcuate nucleus of the hypothalamus

Question 7

Where is GnRH released?

Answer 7

Released into the bloodstream
Travels to the anterior pituitary gland

Question 8

What does the anterior pituitary release?

Answer 8

FSH - follicle stimulating hormone
LH - leutining hormone

Question 9

Where do FSH and LH bind and what do they release?

Answer 9

Bind receptors on different target cells in the ovary
FSH - releases oestrogen
LH - releases progesterone

Question 10

What is the role of oestrogen in the hypothalamic-pituitary-ovarian axis?

Answer 10

• follicular egg maturation
• proliferation of endometrium
• inhibits FSH so regulates the cycle

Question 11

What is the role of progesterone in the hypothalamic-pituitary-ovarian axis?

Answer 11

• renders the endometrium suitable for implanting of a fertilised ovum
• inhibits further release of GnRH, FSH and LH so regulates the cycle and ovulation

Question 12

Describe the follicular phase of the ovarian cycle

Answer 12

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

Question 13

What happens during the ovulation phase?

Answer 13

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

Question 14

What happens after ovulation if no fertilisation takes place?

Answer 14

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

Question 15

Why do progesterone and oestrogen levels drop when there’s non fertilisation?

Answer 15

Due to corpus luteum regression

Question 16

What happens after ovulation if fertilisation takes place?

Answer 16

1) maintains endometrium and pregnancy
2) thicken cervical mucus
3) inhibits further secretion of GRH, FSH and LH which prevents further follicles developing

Question 17

What does the ovum secrete when fertilisation takes place?

Answer 17

Secretes human chorionic gonadotrophin (HCG)
- this stimulates corpus luteum to continue secreting progesterone

Question 18

What’s required to induce follicle formation and ovulation?

Answer 18

GnRH
FSH
LH
They are ER and PR agonists

Question 19

What are oestrogen and progesterone required for?

Answer 19

Required to feedback on hypothalamus and pituitary and so inhibit further follicles being formed
- ER and PR agonists

Question 20

What maintains pregnancy?

Answer 20

Progesterone
- PR antagonist

Question 21

What do oral contraceptives target?

Answer 21

Target the negative feedback system which clamps the secretion of GRH, FH and LH

Question 22

What is eostrogens role in the combination pill?

Answer 22

Eostrogen inhibits the secretion of FSH via the negative feedback loop
- prevents the development of ovarian follicles
- blocks ovulation by blocking the FSH peak

Question 23

What is progesterones role in the combination pill?

Answer 23

Inhibits the secretion of LH
- prevents ovulation by blocking the LH surge
- makes the cervical mucus less suitable for the passage of sperm

Question 24

How long is the combo pill taken for?

Answer 24

21 days
Then a 7 pill free period (causes withdrawal bleeding)

Question 25

How does the progesterone only pill work?

Answer 25

Works by inhibiting LH
- thickens the mucus in the cervix to stop sperm reaching the egg
- blocks ovulation but not consistently so the FSH peak can still occur

Question 26

When is the progesterone only pill taken?

Answer 26

Taken continuously
- can cause irregular periods

Question 27

What is the treatment for ER+ breast cancer?

Answer 27

Tamoxifen - selective estrogen receptor modulator
Anastrozole - aromatase inhibitor

Question 28

Outline the mechanism of action for tamoxifen

Answer 28

It is a competitive inhibitor of estradiol which binds to the estrogen receptor (ER)

Tamoxifen binds to the ER to form a dimer

Then its transported from the cytosol to the nucleus where is binds to DNA to form an unstable complex

Switches off the hormonal growth signal which reduces cell proliferation

Question 29

What is the mechanism of action for anastrozole?

Answer 29

The hormonal growth and survival signal is switched off
- reduces cell proliferation and cell survival

Question 30

What happens in ER positive cancer and how is it treated?

Answer 30

ER drives cancer growth and survival
- tamoxifen is given