Puberty, secondary sexual characteristics, menstrual cycle and contraception Flashcards
What are the six major hormones in sexual characteristics
GOnadotropin releasing hormone
Follicle stimulating hormone
Lutenizing hormone
Oestradiol
Progesterone
Testosterone
Where is gonadotropin releasing hormone formed
Hypothalamus
Where is follicle stimulating hormone made
Anterior pituitary
Where is lutenizing hormone made
Anterior pituitary
Where is oestradiol made and what makes oestrogen
Ovary
OEstrogens= oestradiol+oestrone
Where is progesterone made
Ovary
Where is testosterone made
Testes, adrenal glands, ovary
What hormones are oestradiol and progesterone
Steroid hormones
changes occurring in the menstrual cycle involve interplay between what?
Hypothalamus
Anterior pituitary
Ovary
What happens in the menstrual cycle on days 0-14
GnRH produced in hypothalamus
Stimulates secretion of FSH and LH from pituitary. These act on ovary and stimulate production and secretion of oestradiol from granulosal cells
What does the production of oestradiol cause on days 0-14 of menstrual cycle
Causes a negative feedback loop on anterior pituitary and hypothalamus so stop in both LH and FSH (otherwise there would be uncontrolled secretion)
What happens to oestradiol when LH and FSH levels are falling
Levels are rising
What does FSH act on and what do they do
Granulosal cells of the follicles
-INcrease synthesis of oestradiol
What does LH act on and what does it do
Thecal cells of the follicles to produce androgens
What does cholesterol produce
Androgens and oestrogen’s and glucocorticoids and mineralocorticoids in the adrenal cortex
What is the common step for all steroid hormones and what does this mean
Conversion of cholesterol to pregenelone
-IS the major regulatory stage
What is testosterone derived from
Estradiol
How is oestradiol synthesisesd
FSH acts on granulose cells to produce oestrogen however needs help. Comes from the action of LH on thecal cells
LH binds to its receptor in thecal cells and causes cholesterol to produce androstenedione
Only thecal cells contain receptors to LH and granulose cells to FSH in early stages
Granulose cells do not have enzymes to produce androstenedione. Acramatose activity in granulose cells allows androstenedione to form estradiol when FSH binds
Why do oestradiol levels rise when FSH levels have dropped
Oestrogens bind to receptors in granulosa cells. They are stimulated to proliferate and produce more oestrogen receptors. There is positive feedback- Where oestrogen stimulates further oestrogen output and a surge in circulating oestrogens
What does the production of oestradiol allow the new follicle
TO develop and grow into the Graafian follicle
How does ovulation occur
The high oestradiol levels (late follicular phase) act on the pituitary to release more LH
(At mid cycle the negative feedback becomes positive allowing a short surge of LH to be released)
High oestradiol together with FSH cause change in action of LH
There is stimulation of appearance of LH receptors on granulosal cells and there is an increase in progesterone synthesis
There is a release of oocyte (proteolytic activity to breakdown collagen)
How is the corpus luteum formed
What is it maintained by
What does it secrete and what does this do
What happens to oestradiol levels
Formed from the collapsed follicle
Maintained by LH
Secretes progesterone which maintains endometrium
OEstradiol levels begin to drop because progesterone inhibits oestradiol synthesis
What happens in days 14-28 of the menstrual cycle
Progesterone causes a decrease in gonadotropin secretion (suppresses GnRH)
FSH and LH levels low (no new follicles develop)
What happens if the corpus luteum dies
Decrease in progesterone and oestrodiol levels
Increase in FSH and LH levels
Allows new follicles to mature
Onset of maturation
