adult female reproductive endocrinology

Question 1

at puberty what happens to the hypothalamus

Answer 1

undergoes a desensitization to the negative feedback of gonadal steroids and simultaneously the positive feedback action of estrogen is established

the positive feedback of estrogen brings about the midcycle ovulatory surge of gonadotropins and hence ovulation

Question 2

gonadotropin levels
1-prepuberty
2-approaching puberty
3-completed puberty
4-menopause

Answer 2

1 - FSH>LH, and pulsatile LH is minimal
2 - LH secretion increases during sleep
3 - LH>FSH, and cyclic release occurs
4 - cyclic release stops, and both levels increase

Question 3

what controls the cyclic release of gonadotropins FSH and LH

Answer 3

hypothalamus

Question 4

gonadotropin secretion is highest when?

Answer 4

menopause

Question 5

why is the intermenstrual period longer many times?

Answer 5

the occurrence of anovulatory cycles

• in adolescents this is due to erratic secretion of gonadal steroids and pituitary gonadotropins by an immature hypothalamus
• in perimenopausal time, they are due to a gradual decline in the secretion and negative feedback action of the ovarian steroid hormones

Question 6

menstrual cycle divisions

Answer 6

starts on first day of menses
28 days long
follicular phase
ovulation 
and then luteal phase
**follicular and luteal refer to the state of the ovary

Question 7

follicular phase is characterized by

Answer 7

growth of follicles and enhanced estrogen

–> uterine growth, cervical secretions that favor sperm transport, ovary sensitive to LH and FSH, and LH/FSH surge evoked

Question 8

luteal phase is characterized by

Answer 8

corpus luteum and dominant actions of progesterone

–> uterine quieting, secretions that dont favor sperm transport, and feedback signal to hypothalamus

Question 9

is there overlap in secretions throughout these phases?

Answer 9

yes; dominant ones are just relatively profound

Question 10

gonadotropin secretion during follicular maturation of menstrual cycle leading up to ovulation

Answer 10

FSH induces proliferation of granulosa cells
an aromatizing enzyme converts androgens to estradiol

increased granulosa = increased FSH and LH receptors

then LH acts on theca cells to induce androgen synthesis which diffuses into the granulosa cells (aromatized to estrogen)

estrogen diffuses into general circulation –> provides ovarian signal to hypothalamus for the ovulatory surge of gonadotropins and progesterone

day 14 follicle is ready to ovulate

ovulation 16-24 hours after surge

Question 11

initiation of midcycle surge depends upon…

Answer 11

the hypothalamus sensing a critical profile of estrogen in the circulation during the entire 2 week follicular phase

Question 12

which is higher in surge? LH or FSH

Answer 12

both rise abruptly but LH is alot greater

Question 13

pattern of GnRH release during the surge?

Answer 13

pulsatile

self-priming effect: the gonadotropin response to each consecutive pulse is higher than the last one –> amplifies the ovulatory signal from the hypothalamus

Question 14

GnRH pulsatile vs constant effect

Answer 14

pulsatile - amplifies ovulatory signal to the hypothalamus

constant infusion - inhibit reproductive function

Question 15

negative feedback of estrogen

Answer 15

blood level gonadotropins are low in the follicular phase and the luteal phase when estrogen has negative feedback on hypothalamus, reinforcing progesterone effect

Question 16

positive feedback of estrogen

Answer 16

in follicular phase, estrogen levels rise progressively - unique profile over two weeks that stimulates the hypothalamus

Question 17

what acts on the mature follicle to cause luteinization

Answer 17

LH

Question 18

FSH acts on granulosa cells to cause

Answer 18

cell proliferation
increased LH and FSH receptors (increased sensitivity)
increased estrogen production

Question 19

LH acts on the theca cells to induce

Answer 19

synthesis of androgens which is converted to estrogen by the aromatase enzyme in granulosa cells

Question 20

what event is used as the key starting point when considering the functional sequencce of the menstrual cycle?

Answer 20

rise in FSH that triggers follicular growth

Question 21

luteolysis

Answer 21

life span of the corpus luteum is programmed for abut 14 days then spontaneously regresses
during luteolysis, progesterone and estrogen declines and this leads to vasospasm of the spinal arterioles of the endometrium, endometrial necrosis, desquamation, and bleeding

role of prostaglandins in this process