menstrual cycle

Question 1

When does a new follicle begin to develop in the menstrual cycle?

Answer 1

day 0-7

Question 2

What drives the maturation to a Graafian follicle?

Answer 2

oestradiol

Question 3

On what day does ovulation happen?

Answer 3

14

Question 4

What are the 5 major hormones of the menstrual cycle?

Where are they released from?

Answer 4

GnRH - hypothalamus
FSH - ant pit
LH - ant pit
oestradiol - ovary 
progesterone - ovary

Question 5

Within days 0-14, what are the hormonal changes? (4 things) – GnRH, FSH, LH, Oestradiol

Answer 5

surge in all

oestradiol causes negative feedback on hypothalamus and ant pit

Question 6

Why are FSH and LH levels kept low during days 0-14?

Answer 6

oestradiol

Question 7

Within days 0-14, what do LH and FSH do?

Answer 7

FSH - act on granulosal cells to increase synthesis of oestradiol
LH - thecal cells to produce androgens

Question 8

Go over biosynthesis of oestradiol*

What’s the main precursor molecule?

Answer 8

start from pregnenolone

key intermediate - progesterone

Question 9

Explain the synthesis of oestradiol

What cells involved? Hormones?

Answer 9

binding of FSH causes androstenedione to oestradiol

in the granulosal cell

Question 10

Why does oestradiol continue to rise despite low FSH and LH levels?

Answer 10

oestradiol increases proliferation of granulosal cells = more oestradiol produced (positive feedback)

Question 11

Just before ovulation, what happens in terms of the effect of oestradiol? What does this cause?

Answer 11

at high level act on ant pit to release more FSH and LH

Question 12

At ovulation, the effects of LH change drastically. What causes this change?

Answer 12

high oestradiol + FSH causes change

Question 13

What exactly is the change of action of LH described ^?

Answer 13

now LH binds to granulosal cells instead of thecal cells - cholesterol to form progesterone == now progesterone production

Question 14

What does progesterone trigger?

Answer 14

release of oocyte

Question 15

What maintains the CL (corpus luteum)?
What does it secrete?
What happens to oestradiol levels? Why?

Answer 15

• -LH
• -progesterone
• -oestradiol levels drop (progesterone inhibit oestradiol synthesis)

Question 16

What does progesterone inhibit in the endocrine axis? What’s the effect of this?

Answer 16

causes decrease in GnRH secretion

FSH and LH levels drop = no new follicles

Question 17

When the corpus luteum degenerates: what hormones decrease and what increase?

Answer 17

DECREASE = progesterone and oestradiol

INCREASE = FSH and LH

Question 18

What are the 2 types of hormonal contraceptives? What’s the main principal behind them?

Answer 18

• suppress ovulation = -ve feedback of progesterone on ant pit and hypothalamus
• decrease in GnRH secretion = low FSH and LH, no new follicles

combined oral contraceptive pill - synthetic oestrogen and progesterone (o makes p more effective)

progesterone only pill

Question 19

Why don’t menstrual cycles happen during pregnancy?

Answer 19

high levels of progesterone present

inhibits gonadotrophin secretion

Question 20

Why don’t you get menstrual cycles after menopause?

Answer 20

ovaries dont respond to FSH and LH

low oestradiol levels (follicles dont develop)

Question 21

What do ovarian oestrogens do in terms of female development? What about the androgens?

Answer 21

Ovarian oestrogens regulate growth of breast and female genitalia
androgens from ovary and adrenals control growth of pubic and axillary hair

Question 22

In males? What do steroid hormones (androgens) do?

Answer 22

Testicular androgens control development of genitalia and body hair as well as enlargement of larynx and laryngeal muscles.