Pathophysiology

Question 1

Describe follicular phase of menstrual cycle

inc. hormones involved and how many days

Answer 1

Follicular phase (first 14 days - but can differ if cycle is longer than 28 days)

Hypothalamus → GnRH → stimulates anterior pituitary gland → FSH → stimulates growth of follicles → oocyte (developing egg) form into ovum (mature egg) inside follicles → inc. oestrogen levels → causes -ve feedback on pituitary gland and hypothalamus → decreased FSH and LH levels during this phase

Question 2

Describe ovulation phase of menstrual cycle

inc. hormones involved and how many days

Answer 2

Ovulation (middle of cycle)

Oestrogen levels reach threshold → trigger switch to +ve feedback → inc. GnRH → surge of LH occurs → triggers ovulation → release of mature egg from follicle
+ Inc. oestrogen levels → cervical mucus inc. permeability to sperm for implantation

Question 3

Describe luteal phase of menstrual cycle

inc. hormones involved and how many days

Answer 3

Luteal phase (always last 14 days)
After ovulation → ruptured follicle → becomes corpus luteum → secretes inc. progesterone and small amounts of oestrogen → Inc. progesterone = thickened endometrium for implantation of fertilised egg + less permeable to sperm

If fertilisation doesn’t occur = corpus luteum degenerates → dec. progesterone and oestrogen levels → signals endometrium to shed and menstruation occurs.

Question 4

Describe hormonal changes in puberty

Answer 4

Initially → GH secreted → stimulates growth spurt

Hypothalamus → GnRH → pituitary gland → FSH + LH → inc. oestrogen + progesterone levels

1 year before menarche → FSH levels plateau and LH levels continue to rise and spike right before menarche