Sex hormones and oral contraceptives (L18)

Question 1

what is the hypothalamic-pituitary-ovarian axis/tract?

Answer 1

part of the endocrine system

GRH released from the hypothalamus and acts on the anterior pituitary which releases FSH and LH

surge in LH causes ovulation

Question 2

physiological effects of oestrogen on the endometrium

Answer 2

sensitises LH releasing cells in the pituitary - encourages them to release LH

proliferation of the endometrium

inhibits FSH so regulates cycle

Question 3

physiological effects of progesterone on the endometrium

Answer 3

renders the endometrium suitable for implanting of a fertilised ovum

maintains endometrium

inhibits further release of GRH, FSH and LH so regulate cycle and ovulation

Question 4

negative feedback regulation of the hypothalamic-pituitary-ovarian axis

Answer 4

leads to inhibition of GRH, FSH and LH

ensures only 1 egg is released at a time

Question 5

what are the 2 options after ovulation

Answer 5

fertilisation

no fertilisation

Question 6

what happens if there is no fertilisation after ovulation?

Answer 6

corpus lute regresses
progesterone levels drop

endometrium cannot be maintained so menstruation occurs

lack of progesterone means clamp on GRH, FSH and LH secretion is released - cycle can start again

follicle development occurs again

Question 7

what happens if there is fertilisation after ovulation?

Answer 7

fertilised ovum is implanted and secretes human chorionic gonadotrophin (HCG) which stimulates the corpus lute to continue secreting progesterone

maintains endometrium and pregnancy

inhibits further secretion of GRH, LSH, and LH preventing further follicle development

Question 8

what do GRH, FSH and LH do?

Answer 8

required to induce follicle formation and ovulation

Question 9

what does oestrogen do?

Answer 9

required to induce proliferation of endometrium

Question 10

what does progesterone do?

Answer 10

required to maintain pregnancy

required to feedback on hypothalamus and pituitary to inhibit further follicle formation

Question 11

what are the important targets in regulating ovulation and pregnancy?

Answer 11

GRH, FSH and LH

oestrogen

progesterone

feedback control on hypothalamus and pituitary

Question 12

GRH, FSH and LH as targets in regulating ovulation and pregnancy

Answer 12

block them with a selective antagonist

inhibits follicle and corpus lute formation and prevents ovulation

however:
• blocking them results in loss of oestrogen and progesterone
• oestrogen required in normal female physiology - without it causes pharmacological menopause

GRH agonists are used to aid fertility

Question 13

oestrogen as a target in regulating ovulation and pregnancy

Answer 13

oestrogen antagonist useful in preventing proliferation of the endometrium

however, oestrogen required in normal female physiology

oesterogen antagonists used to treat a number of oestrogen dependent cancers

Question 14

progesterone as a target in regulating ovulation and pregnancy

Answer 14

progesterone antagonists useful in terminating pregnancy

mifepristone, a progesterone antagonist, is used as a morning after pill

Question 15

feedback onto hypothalamus and pituitary as a target in regulating ovulation and pregnancy

Answer 15

by progesterone

oral contraceptives target the negative feedback system clamping the secretion of GRH, FSH and LH

Question 16

how do oral contraceptives work?

Answer 16

they trick the hypothalamus into thinking the woman is pregnant

Question 17

what are the 2 types of oral contraceptives?

Answer 17

combined pill - oestrogen and progesterone

mini pill - progesterone only

Question 18

the combined pill

Answer 18

oestrogen inhibits secretion of FSH via negative feedback
• this prevents development of new follicle

progesterone inhibits secretion of LH preventing ovulation and makes cervical mucus less suitable for passage of sperm

taken for 21 days then 7 pill free period to have withdrawal bleeding

Question 19

progesterone only pill

Answer 19

mainly effective due to effect on cervical mucus

doesn’t actually block ovulation

taken continuously

less reliable

Question 20

side effects of oral contraceptives

Answer 20

• weight gain
• water retention
• mild nausea
• skin changes
• amenorrhoea

Question 21

what is amenorrhoea?

Answer 21

lack of menstrual period in a woman of reproductive age

Question 22

more severe side effects of oral contraceptives

Answer 22

vascular
• DVT
• myocardial infarction (heart attack) increased
• stroke increased

GI
• jaundice

mental
• depression

cancer
• may increase or may decrease

Question 23

why does breast feeding have a contraceptive affect?

Answer 23

baby sucking causes hypothermic nuclei to secrete prolactin releasing factor (PRF) which causes anterior pituitary to release prolactin

Question 24

regulation of milk production by prolactin

Answer 24

prolactin is the only anterior pituitary hormone than only acts to negatively feedback

inhibits release of GRH and FSH and everything else downstream

breast feeding has a natural contraceptive effect of 6 months

Question 25

other methods of contraception other than oral contraceptives

Answer 25

male contraception

non-hormonal contraceptives - IUD/coil

condom