Menstrual Cycles

Question 1

Menarche - start of menstrual cycle

Amenorrhoea (absence of periods)

Answer 1

Menarche:
2-3 yrs after thelarche
Soon after peak height velocity (PHV)
Mean age 12.7 years (range 10.7-16.1 yrs)

Primary amenorrhoea:
Later than 16 yrs is regarded as abnormal

Secondary Amenorrhoea:
Common for periods to be irregular/anovulatory for first 18 months
Periods start but then stop for at least 3-6 months

Question 2

Menstrual cycles in adult women
Length of menstrual cycles?
What is Amenorrhoea?
What is oligomenorrhoea?

Answer 2

Menstrual cycles:
28 day cycle (24-35)
+/- 2 days each month

Amenorrhoea- absence of periods
No periods for at least 3-6 months
Or up to 3 periods per year

Oligo-menorrhoea - few periods
Irregular or infrequent periods > 35 day cycles
4-9 cycles per year

Question 3

Menstrual cycle - follicular phase

Answer 3

1. Folicle stimulating hormone (FSH) rises
2. 2-3 follicles start to grow
3. Produce E2 and Innibin B
4. These reduce FSH by -ve feedback
5. Restrict FSH window and non dominant follicles undergo atresia

Question 4

Follicular phase (pre-ovulatory phase)

Answer 4

6. A dominant Graafin follicle emerges
7. E2 continues to increase
8. Switch to +ve feedback by high E2 (oestradiol)
9. Induced luteinising hormone (LH) surge

Question 5

Menstrual cycle
Ovarian cycle
Endometrium - menstrual phase, proliferative phase (oestradiol), secretory phase (progesterone)

Answer 5

Ovarian cycle: 
Follicular phase (1-13) -> ovulation (day 14) -> luteal phase (day 14-28) (oestrogen + oestradiol) 

Endometrium: 
Menstrual phase 
Proliferative phase (oestradiol) - endometrial lining regrows, growth of new epithelial cells, gland proliferation, increase in stroma/arterioles 
Secretory phase (progesterone) - transformation to be receptive for implantation, increased vol of stroma cells >>> thick spongy lining, coiling and lengthening of spiral arteries