Hormonal control of menstrual cycle + disorders Flashcards
What effect does oestrogen have on pit
Low oestrogen inhibits LH release
High oestrogen stimulates it (this feedback loop works by increasing no. of oestrogen receptors)
What effects does progesterone have on pit
Low prog stimulates LH and FSH
High prog inhibits it (this feedback loop works by increasing sensitivity)
What is the most important hormone in follicular stage
FSH ( can rise as O, P and inhibin are low)
What are the two types of cell in follicle
Thecal - make androgens from cholesterol
Granulosa - make oestrogens from androgens (aromatisation) - under influence
What do inhibin and activin do
Both secreted by granulosa cells
Inhibin increases androgen synthesis and down regulates FSH
Activin increases FSH binding onto follicles
What causes LH surge
oestrogen exceeding positive threshold
How and why does ovulation occur
after breakdown of follicle by LH, FSH, proteolytic enzymes and PG
What are the actions of LH
Luteneises follice - makes it start producing prog
Resumption of meiosis
ovulation
Why does corpus luteum degrade
Degrades as prog switches FSH and LH off and there’s no b-hCG to tell it to keep going on
How does menstrual cycle start again
Reduction of P + O and inhibin, brake taken off pituitary and FSH starts again
What change occurs in proliferative endometrial phase
Single layer –> pseudostratified
What happens in secretory endo. phase
Proliferation stops, start secreting stuff into glands and uterine lumen
Formation of decidua (temporary layer)
What are the three layers of endometrium
Basalis (REMAINS)
spongiosum (stroma + exhausted glands)
compactum (decidua)
Definition of precocious puberty
Before 8 in a girl
before 9 in a boy
Definition of delayed puberty
No secondary sexual characteristics by age of 14