Female Sex Hormones

Question 1

What are the principal steroid hormones secreted by the adult ovary?

Answer 1

Estradiol

Progesterone

Androstenedione

Question 2

What is the primary source of estrogens in the non-pregnant adult?

Answer 2

Maturing follicle

Question 3

What is estradiol (E2)?

Answer 3

Principal ovarian estrogen

Most potent

Question 4

What is estrone (E1)?

Answer 4

Formed from estradiol and androstenedione by peripheral conversion

Fat is a major source of aromatase activity

Question 5

What is estriol (E3)?

Answer 5

Weak estrogen

Levels are only usually measured during pregnancy

Placenta synthesized large amounts of E3 during pregnancy

Question 6

What two cells in the follicle are responsible for estrogen synthesis?

Answer 6

Thecal cells

Granulosa cells

Question 7

What are thecal cells?

Answer 7

Close proximity to blood vessels, source of LDL

Have enzymes to synthesize androgens

Do not produce aromatase, so can’t convert androgens to estrogens

Androstenedione production

Question 8

What are granulosa cells?

Answer 8

Unable to synthesize androgens

Have high aromatase activity, so they can convert androgens from thecal cells to estrogens

Also expresses 17B-HSD, which converts estrone to estradiol

Question 9

Describe the hormonal control of thecal and interstitial cells of the ovary.

Answer 9

Possess LH receptors

LH induces androgen biosynthesis via cAMP pathway

Question 10

Describe the hormonal control of granulosa cells?

Answer 10

Expression of aromatase induced by FSH via cAMP pathway

Question 11

What are progestins?

Answer 11

Steroids that promote gestation

Progesterone is the most potent

Principal sourc is the corpus luteum

Question 12

What is the principal circulating androgen in women?

Answer 12

Testosterone

Question 13

What are the three phases of the reproductive cycle?

Answer 13

Follicular phase

Ovulatory phase

Luteal phase

Question 14

What is the follicular phase?

Answer 14

Begins with the onset of menstrual bleeding

Preovulatory follicle develops within the ovary

Estradiol primary hormone

Corresponds to menstrual and proliferative phases of the endometrial cycle

Question 15

What is the ovulatory phase?

Answer 15

Lasts approximately 36 hours and culminates in ovulation

Question 16

What is the Luteal phase?

Answer 16

13-14 days

Corpus luteum and ovary secretes both progetsone and estradiol

Corresponds to the secretory phase of the endometrial cycle

Question 17

What is the primordial follicle?

Answer 17

Primary ooctye surrounded by a single layer of poorly differentiated pregranulosa cells

Question 18

Describe recruitment of primordial follicles

Answer 18

Begins in fetal life and continues in wave-like fashion until the supply is depleted at menopause

Question 19

What occurs to follicular growth prior to puberty?

Answer 19

Follicular growth occurs but the process is arrested in an early stage

Follicle undergoes atresia

Question 20

What is a primary follicle?

Answer 20

Primordial follicle leaves the pool of inactive follicles

Zona pellucida forms around the oocyte

Oocyte and granulosa cells increase in size

Question 21

What extracellular proteins are secreted by the oocyte during the formation of a mature preantral follicle?

Answer 21

ZP1, ZP2, ZP3

Provide species-specific binding sites for sperm cells

Question 22

How do the granulosa cells mature during mature preantral follicle formation?

Answer 22

Oocyte releases paracrine factor that stimulate the growth and differentiation of the granulosa cells

Granulosa cells begin to express FSH and estrogen receptors

Question 23

What is the difference between early antral follicles and Larger antral follicles?

Answer 23

Early antral follicles - responsive to FSH, but considered to be FSH independent

Large antral follicles - Highly dependent on FSH for growth and survival

Question 24

What factors promote atresia in oocytes and granulosa cells?

Answer 24

Tumor necrosis factor a (TNFa)

Androgens

IL-6

Question 25

What are the two populations of granulosa cells that appear due to the swelling of the antral cavity?

Answer 25

Mural cells - close to thecal layer, engaged in steroidogenesis Cumulus cells - surround oocyte, facilitate the capture of the oocyte by the ciliated fallopian tubes

Question 26

What is the gonadotropin-dependent phase of follicular growth?

Answer 26

Cohort of growing antral follicles is recruited, but only dominant follicle survives Survival of follicles that enter this stage of rapid growth is dependent upon FSH

Question 27

When does cyclic recruitement occur?

Answer 27

During the late luteal phase of the preceding cycle

Question 28

When is the dominant follicle selected?

Answer 28

Early follicular phase of the current cycle

Question 29

What indicates the presence of a dominant follicle?

Answer 29

Dramatic increase in circulating estradiol levels Ovulation occurs about 10-14 days after a follicle is selected

Question 30

What is the role of FSH during the follicle selection process?

Answer 30

FSH stimulates granulosa cell proliferation and estradiol synthesis Estradiol works syntergistically with FSH to promote granulosa cell proliferation Estradiol and inhibit have a negative feedback effect on FSH release by the anterior pituitary

Question 31

How does the dominant follicle inhibit the development of less mature follicles in the cohort?

Answer 31

Through the negative feedback by E2 on FSH release The other follicles will undergo atresia FSH containes within the follicular fluid of the dominant follicle helps it sustain the falling FSH levels

Question 32

Why can granulosa cells respond to the LG surge?

Answer 32

FSH induces the expression of LH receptors

Question 33

What factors influence the growth of the dominant follicle in the presence of declining levels of FSH?

Answer 33

More FSH receptors Produces IGF-1, enhancing responsiveness to FSH FSH induces LH receptor expression Follicular fluid has FSH Better developed vascular supply

Question 34

What is the stigma?

Answer 34

Poorly vascularized bulge in the ovary created by the pressure of the follicle

Question 35

What is cumulus expansion?

Answer 35

Increase in size of the cumulus-oocyte complex due to secretion of ECM components in response to LH stimulation

Question 36

What s the signal required to induce ovulation?

Answer 36

LH surge Result of a positive feedback effect of estradiol on the pituitary and hypothalamus

Question 37

What are the specific actions of LH on the preovulatory follicle?

Answer 37

Release of hydrolytic enzymes Expression of COX-2 and progesterone receptors Resumption of meiosis via growth factor release Promotes cumuls expansion Promotes reorganization of follicle into the corpus luteum

Question 38

What is the corpus luteum formed from?

Answer 38

Remnants of the ruptured follicle Mural granulosa cells and thecal cells differentiate into granulosa- and thecal-lutein cells

Question 39

How does LH promote angiogenesis?

Answer 39

Inducing the granulsa-lutein cells to secrete VEGF

Question 40

Why are granulosa-lutein cells able to obtain cholesterol from circulating LDL and HDL?

Answer 40

LH induces breakdown of basal lamina LH induces LDL and HDL receptor expression

Question 41

How does LH induce steriodogenesis in granulosa-lutein cells?

Answer 41

Induces expression of StAR Since these cells do not express androgen synthesis enzymes, they release progesterone

Question 42

What causes luteolysis?

Answer 42

Decline in LH production due to negative feedback effects of estrogen and progesterone

Question 43

What occurs to the corpus luteum in pregnant women?

Answer 43

Corpus luteum is maintained due to human chorionic gonadotropin (hCG)