Endocrine 07

Front 1

Describe GnRH release

Back 1

GnRH is released in a pulsatile manner and that triggers FSH and LH secretion

Front 2

What does FSH do in females?

Back 2

Stimulates follicular growth and induces LH receptors on the growing follicle

Front 3

What does LH do in females?

Back 3

-Stimulates steroidogenesis
-Is responsible for the midcycle surge and ovulation.
-Later in the cycle keeps the corpus luteum alive

Front 4

What hormone is responsible for the midcycle surge and ovulation?

Back 4

LH

Front 5

What hormone keeps the corpus luteum alive?

Back 5

LH

Front 6

What hormones does the ovary make?

Back 6

-Estrogen
-Progesterone

Front 7

Describe the feedback loops that involve estrogen

Back 7

Negative feedback: Estrogen normally turns off LH and FSH secretion

Positive Feedback: High levels of estrogen and a fast rise in estrogen in the midfollicular phase stimulate a positive feedback loop

Front 8

Describe the feedback loop state in patients with polycystic ovarian syndrome

Back 8

Stuck in the positive feedback. They have high estrogen and FSH and LH are not suppressed

Front 9

Describe sexual differentiation into a female

Back 9

1. The default path

2. The primordial gonad turns into an ovary if you do not have testicular determining factors

3. No testes form so there will be no inhibition of female reproductive structures

Front 10

Describe Germ cell numbers in the ovary throughout life

Back 10

1. At a fetal age of 5 months there are approximately 7 million germ cells

2. At birth many of these have been lost and there are between 1-2 million

3. As you enter menarche you have approximately 400k and they are slowly lost

4. All of them disappear with menopause

Front 11

Describe the decline in germ cell numbers through life

Back 11

A primary ovarian process, not dependent on LH or the pituitary

Front 12

Describe puberty and the pattern of LH secretion

Back 12

1. Puberty starts at night
2. There is some small secretion pulses in prepuberty
3. Larger pulses develop during sleep in midpuberty
4. The trigger for LH pulses in puberty is not known, but leptin and body fat are important in this process
5. The adult pattern develops as you mature and the positive and negative feedbacks develop

Front 13

Describe the events of puberty in the female

Back 13

1. Breast budding occurs first at the mean age of 10 as a result of gonadal maturation
2. Pubic hair begins to develop around the age of 10.5 from adrenal androgen secretion
3. Growth spurt occurs around 11.4yo from estrogen from the ovary
4. There is maturation of the positive feedback loop, ovulation, and the first menstrual period around age 13
5. Adult breast develop and adult pubic hair develop eventually occur

Front 14

Describe puberty in a patient with Turner's syndrome

Back 14

There are no ovaries so there is no estrogen develop, however the adrenal glands are fine so there will still be adrenarchy

Front 15

Describe Tanner staging

Back 15

I is the prepuvital stage
V is the adult stage

Staging will tell you when someone enters puberty and if there is a problem

Front 16

What are the two phases of the menstrual cycle?

Back 16

1. Follicular phase is everything before the LH surge and ovulation
2. Luteal phase is everything after

Front 17

Describe hormone levels through the menstrual cycle

Back 17

1. At day 1 Estrogen, FSH, and LH levels are low
2. FSH and LH levels begin to rise
3. This begins to stimulate estrogen secretion
4. This causes recruitment of a cohort of follicles and then a rapid rise in estrogen
5. The estrogen positive feedback loop occurs and there is an LH surge
6. This causes ovulation
7. Post-ovulation estrogen levels drop and LH goes down but still remains high
8. LH causes the corpus luteum to continue to make estrogen and progesterone
9. Estrogen and progesterone secretion continues for 12-14 days
10. If nothing happens the corpus luteum dies, involvutes, and estrogen levels rapidly decline followed by progesterone decline
11. This causes the next menstrual cycle to begin

Front 18

Describe the significance of measuring progesterone

Back 18

Indicates ovulation. If there is no increased progesterone there was no ovulation

Front 19

What is responsible for the bleeding in menstruation?

Back 19

Steroid withdrawal because the endometrium has been stimulated by estrogen and progesterone. When these levels fall menstruation occurs

Front 20

Describe changes in the basal body temperature throughout the menstrual cycle

Back 20

Progesterone increases basal body temperature a little bit. After ovulation it increases a bit.

Front 21

Describe hormone changes if fertilization/pregnancy occurs

Back 21

1. hCG secreted from the placeta stimulates the corpus luteum
2. hCG takes over for LH and progesterone levels do not fall
3. The corpus luteum will survive and begin to maintain the early pregnancy

Front 22

Describe hormone levels in someone who has a hypothalamic pituitary problem suppressing LH and FSH totally

Back 22

There will be suppressed gonadotropins, estradiol, and progesterone

Front 23

Describe hormone levels in patients with polycystic ovarian syndrome

Back 23

You don’t have an ovulatory cycle because you are not really recruiting a group of follicles. You do not get the FSH stimulation, this nice positive feedback or the estrogen secretion. You never ovulate, you just have high estrogen ammenorrhea.

Front 24

What does high estrogen amenorrhea indicate?

Back 24

Polycystic ovarian syndrome

Front 25

What does low estrogen amenorrhea indicate?

Back 25

Hypothalamic amenorrhea

Front 26

Describe hormone dependence in follicular development

Back 26

1. The primordial follicle and primary follicle stages are hormone independent
2. Secondary and tertiary follicles depend on FSH and LH

Front 27

Describe the effect of FSH and LH on secondary and tertiary follicles

Back 27

1. LH stimulates androgen secretion in the theca layer
2. These androgens then diffuse into the granulosa layer and under FSH stimulation are aromatized to estrogen
3. The follicle grows
4. One follicle is recruited which then continues to grow and rapidly make estrogen
5. The rapid increase in estrogen triggers the LH surge and the follicle ovulates and turns into the corpus luteum
6. The corpus luteum is maintained by LH to make progesterone

Front 28

What occurs with follicle stimulation is there is not enough FSH?

Back 28

1. Follicular growth is not stimulated
2. You dont get normal aromatization and you build up androgens

Front 29

Describe steroidogenesis in the female

Back 29

1. There are 2 pathways:
a. Δ4 occurs in the ovary
b. Δ5 occurs in the adrenals where you get dehydroepiandrosterone secretion

Front 30

Describe the relationship between the Δ4 and Δ5 pathways is steroidogenesis

Back 30

Δ5 products can be converted into Δ4 products:
a. Pregnenolone to progesterone
b. 17-hydroxypregnenolone to 17-hydroxyprogesterone
c. dehydroepiandrosterone to androstenedione

Front 31

Describe androstenedione

Back 31

1. Can be converted back and forth to testosterone
2. Both androstenedione and testosterone can be aromatized to estrone and estradiole, respectively

Front 32

Describe how estrogen secretion in women develops

Back 32

There is aromatization of androstenedione and testosterone to make estradiol and estrone