Female Reproductive Endocrinology - RS

Question 1

What happens during the follicular phase? What hormones mediate it?

Answer 1

Growth and maturation of a primordial follicle during the follicular phase. FSH and rising estradiol

Question 2

What happens during the ovulatory phase? What hormones mediate it?

Answer 2

Rupture of a mature Graafian follicle and oocyte discharge during the ovulatory phase at mid-cycle. LH surge.

Question 3

What happens during the luteal phase? What hormones mediate it?

Answer 3

Conversion of the ruptured follicle to a corpus luteum during the luteal phase. LH, high progesterone and some estradiol.

Question 4

What happens to the corpus luteum if fertilization doesn’t occur? What hormones mediate it?

Answer 4

Degeneration of the corpus luteum to form a corpus albicans proceeds if fertilization does not occur. Low estrogen and progesterone

Question 5

What happens to the primordial follicle during the ovarian cycle? What does it contain?

Answer 5

It increases in size. It contains the ovum, thecal and granulosa cells.

Question 6

What do the granulosa cells function to do?

Answer 6

They make estrogen

Question 7

What do the thecal cells do?

Answer 7

They make precursors of estrogen from LDL

Question 8

What does estradiol (during the follicular phase) do to the uterus?

Answer 8

It promotes proliferation and primes the uterus for the actions of progesterone (by increasing receptors of progesterone).

Question 9

What does progesterone (during the luteal phase) do to the uterus?

Answer 9

It converts it from a proliferative uterus to a secretory one.

Question 10

What hormone dominates the proliferative phase? How long does this phase last for?

Answer 10

The proliferative phase is dominated by estrogens and is variable in length (ave ~14 days in a standard 28 day cycle), thus accounting for the observed range of menstrual cycle lengths

Question 11

What hormone dominates the secretory phase? How long does this phase last for?

Answer 11

The secretory phase is dominated by progesterone and has a fixed length of 14 days following ovulation. Progesterone promotes accumulation of glycogen, increased glandular secretions, and increased vascularity.

Question 12

What hormone dominates the menstrual phase? How long does this phase last for?

Answer 12

The menstrual phase lasts about 5 days and is associated with prostaglandin-mediated vasoconstriction of spiral arteries and local ischemic injury/inflammation. This phase is associated with regression of the corpus luteum.

Question 13

Which cell type does LH act on?

Answer 13

Thecal cells to produce androgens. It primes the cell to convert cholesterol to androstenedione.

Question 14

Which cell type does FSH act on?

Answer 14

Granulosa cells to produce estrogen. Androstenedione is converted to estradiol by aromatase.

Question 15

What effect does GnRH have on the pituitary?

Answer 15

GnRH stimulates release of LH and FSH by the pituitary; estrogen synthesized by developing ovarian follicles has negative feedback effects on the axis

Question 16

What is the exception to the action of estrogen in the late follicular phase (early ovulatory phase)?

Answer 16

In the late follicular phase, blood estradiol reaches a high level that initiates positive feedback and a surge in LH and FSH release, provoking ovulation

Question 17

What dominates in the luteal phase? What is the action of inhibin?

Answer 17

Negative feedback. Inhibin only acts on the anterior pituitary. It inhibits FSH (not LH).

Question 18

During the follicular phase how is LH secreted?

Answer 18

It is secreted in pulsatile waves and increases in amplitude. Pulsatile release of GnRH and pulsatile secretion of LH: High circulating estrogens during the late follicular phase sensitize the anterior pituitary gonadotrophs to stimulation by GnRH, thereby producing the mid-cycle surge in LH (and FSH) release that is necessary for rupture of the growing follicle and ovulation

Question 19

Explain gonadotropin secretion:

Answer 19

GnRH binds to a G-protein-coupled receptor on the gonadotroph membrane, triggering the IP3/DAG signaling pathway. Stimulation causes the gonadotrophs to synthesize and release two gonadotropins: FSH & LH that are stored in secretory granules. Both FSH and LH are glycoprotein heterodimers comprised of common alpha-subunits and unique beta-subunits.

Question 20

What does aromatase make? Where is it found?

Answer 20

Estrogen. The granulosa cells.

Question 21

What are the effects that estrogen has on the body?

Answer 21

proliferation of the uterine endometrial stroma & development of endometrial glands
Proliferation & development of mucosal lining of the fallopian tubes
Stimulation of bone growth by inhibition of osteoclastic activity
Increased fat deposition in subcutaneous tissues

Question 22

What are the effects of progesterone on the body?

Answer 22

Secretory changes in the uterine endometrium (of major importance)
Decreased frequency & intensity of uterine contractions
Increased fallopian tube secretions
Promotes development of lobules and alveoli in breasts

Question 23

Before puberty what inhibits the release of gonadotropins? How is this different from an adult?

Answer 23

In childhood, even very low estrogen levels are sufficient to fully suppress gonadotropin output. In adolescence, higher levels of estrogens are required. In the adult woman, estrogens must be at very high levels to suppress gonadotropin release

Question 24

What is the age dependence on the feedback sensitivity?

Answer 24

Very high sensitivity when young. Much lower sensitivity when older.

Question 25

What happens to GnRH release during puberty?

Answer 25

puberty is when pulsatile secretion of GnRH is observed first at night, and then during the day as well as night.

Question 26

What is menopause?

Answer 26

When cyclic reproductive function and menstruation cease.

Question 27

At menopause what happens to ovarian follicles?

Answer 27

There are virtually no ovarian follicles to respond to FSH & LH, leading to a dramatic decline in steroid hormone production. There is ongoing atresia of cells throughout the reproductive lifetime, thereby accounting for most of the loss of follicles.

Question 28

What happens to gonadotropin levels in menopausal women?

Answer 28

The amounts of circulating gonadotropins increase dramatically after menopause (10- 20-fold) due to the loss of negative feedback on the pituitary and hypothalamus by estrogens and progestogens.
The increase in LH and FSH is due to increased production, not a change in clearance.
Immunoassay of FSH & LH is often used to determine if a woman has gone through the menopause.

Question 29

What is the postmenopausal source of estrogen?

Answer 29

Production of estrone by muscle and adipose tissue, derived primarily from androstenedione in the adrenal gland (and ovary), provides a postmenopausal source of the estrogen, estrone.
Estrone is ~15%-25% as potent as estradiol.
Since many of the symptoms of the menopause are due to estrogen deficiency, the functionality of this system accounts in part for the observation that some women are less disturbed by menopausal symptoms than others.