The Menstrual Cycle Flashcards

1
Q

A high frequency of GnRH pulses (one every 60-90 mins) is going to selectively promote the secretion of which hormone?

A

LH

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2
Q

A low frequency of GnRH pulses (one pulse every 120 mins) is going to selectively promote the secretion of which hormone?

A

FSH

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3
Q

Define Luteolysis.

A
  • When the Corpus Luteum regresses and dies in the the absence of fertilization and implantation
  • Leads to a drastic decline in levels of progesterone, estrogen, and inhibin A by day 24 of the menstrual cycle
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4
Q

A rise in FSH is going to cause what to happen in the ovary?

A
  • Recruitment of Large Antral Follicles

- These follicles produce low levels of Estrogen and Inhibin B

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5
Q

Explain why the LH/FSH ratio is going to slowly increase throughout the follicular phase.

A
  • Slow rise in estrogen and inhibin B will decrease FSH secretion
  • Loss of High levels of PROGESTERONE will cause an increase in GnRH pulses; thus, secreting more LH
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6
Q

What is the Ovary’s response to a decline in FSH?

A

Follicular Atresia (except for the dominant follicle)

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7
Q

The dominant follicle is going to survive because it has the highest number of FSH receptors on it. What else happens to the dominant follicle?

A
  • Produce increasing amounts of Estradiol-17B and Inhibin B during the second half of the follicular phase
  • FSH will also induce the expression of LH receptors in the mural granulosa cells
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8
Q

Explain the mechanism underlying the midcycle LH surge in the Anterior Pituitary.

A
  • High Levels of Estrogen will exert a POSITIVE Feedback on the gonadotrope, producing the midcycle LH surge
  • Occurs largely at the level of the PITUITARY
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9
Q

Describe the three outcomes that are occuring in the ovary in response to the LH surge.

A
  1. Primary Oocyte will complete meiosis I and arrests at Metaphase of meiosis II
  2. Wall of the follicle and of the ovary at the stigma is broken down and the free-floating Cumulus-oocyte complex is kicked out of the ovary. Normally occurs 32-36 hours after the onset of LH surge.
  3. Mural Granulosa cells and Thecal Cells are reconstructed to form the CORPUS LUTEUM
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10
Q

How does the mature Corpus Luteum exhibit negative feedback on the Pituitary Gonadotrope?

A
  • Rising levels of Progesterone, Estrogen, and inhibin A are going to provide the Negative Feedback to the Pituitary Gonadotrope
  • HIGH Progesterone levels will BLOCK any Positive Feedback that Estrogen could provide
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11
Q

What is required for normal Corpus Luteum function? How many days will it take the corpus luteum to regress? Describe the overall changes in hormone levels that will take place if there is no pregnancy.

A
  • Corpus Luteum will become insensitive to LH signaling unless it receives it from another source (hCG from an implanted embryo)
  • Corpus Luteum will normally regress in 14 days
  • Progesterone and Estrogen levels will start to decline by about 10 days within the Luteal Phase
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12
Q

What happens when you remove the negative feedback at the end of the menstruation cycle?

A

Increase in FSH and the cycle will start all over again!

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13
Q

Describe the frequency of GnRH pulses over the menstrual cycle.

A

Second Half of Follicular Phase: Increase Pulses

Luteal Phase: Decrease Pulses

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14
Q

Define: Thelarche, Adrenarche and Menarche.

A

Thelarche: Breast Development
Adrenarche: Increase in Adneral Androgen Secretion
Menarche: Beginning of Menstrual Cycles

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15
Q

Describe the Pattern of Gonadotropin levels throughout the life of a Female.

A

Childhood: FSH and LH levels are going to be low

Puberty: FSH and LH are going to increase but ONLY at night

Reproductive Years: FSH and LH are going to be increased both day and night

Menopause: FSH and LH are both HIGH

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16
Q

What are the two cycles that are happening during the menstrual cycle?

A
  1. Ovarian Cycle

2. Endometrial Cycle

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17
Q

During which days of the menstrual cycle do the Follicular and Luteal Phases occur?

A
  • Follicular Phase: 0-14 Days

- Luteal Phase: 14-28 Days

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18
Q

Describe the feedback mechanism of Estrogen at LOW and HIGH hormone concentration levels.

A
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19
Q

List the functions of Estrogen.

A
  • Stimulate Bone and Muscle Growth
  • Stimulation of Endometrial Growth
  • Maintain Female Secondary Characteristics
  • Maintain Glands
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20
Q

Name the three hormones that the Corpus Luteum is going to secrete.

A
  1. Estrogen
  2. Inhibin (Inhibits FSH)
  3. Progesterone (Inhibits GnRH & stimulates endometrial growth)
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21
Q

Explain how GnRH is going to be suppressed after ovulation in the Luteal Phase.

A
  • Progesterone Levels will INCREASE

- Estrogen Levels will DECREASE slowly

22
Q

What are the three phases of the Endometrial Cycle?

A
  1. Menses
  2. Proliferative Phase
  3. Secretory Phase
23
Q

Females have both Inhibin A and B. During which phase will they both predominantly exist?

A

Inhibin B: Follicular Phase

Inhibin A: Luteal Phase

24
Q

What is the overall purpose of the Follicular Phase?

A

Growth and Release of Dominant (Graffian) Follicle

25
Q

The Luteal phase is going to occur simultaneous with which endometrial Phase?

A

Secretory Phase

26
Q

The Follicular Phase is going to occur simultaneous with which endometrial Phases?

A

Menses and Proliferative Phases

27
Q

What are the secretory products of Theca and Granulosa Cells?

A

Theca Cells: Androgens and Progestins

Granulosa Cells: Inhibins, Activins, Estrogens and Progestins

28
Q

Which Receptors are going to be present on Theca and Granulosa Cells?

A

Theca Cells: LH

Granulosa Cells: LH and FSH

29
Q

Describe the function of Activins released from the Granulosa Cells.

A

STIMULATES the release of FSH from the Anterior Pituitary

30
Q

Describe the Cellular Pathway of Action that GnRH is going to act through.

A
  • Acts through Gq Receptor
  • Activates IP3 and DAG
  • Increase in INTRACELLULAR Ca2+ levels and you will have release of Gonadotrophs!
31
Q

Explain why the secretion of GnRH is going to be lower during the Early and Late Follicular Phases. What is the main driver for the increase in GnRH sensitivity?

A

The Gonadotrophs become MORE SENSITIVE to GnRH as you move through the follicular phase
- Driven by the POSITIVE Feedback mechanism from Estrogen

32
Q

Which hormone is important for acting on the Corpus Leteum after Ovulation?

A

LH

33
Q

Describe the Structure of Activins and Inhibins.

A
  • Activins: Dimers with B-subunits (Disulfide Bonds)

- Inhibins: Dimers with A- and B-subunits (Disulfide Bonds)

34
Q

Which Cell in the Ovary is going to have Aromatase Activity?

A

GRANULOSA CELLS!

35
Q

Which cell in the Ovary is going to be responsible for creating Androstenedione?

A

Thecal Cells

36
Q

What is going to be the main products of the Thecal Lutein and Granulosa Lutein Cells?

A

Thecal Lutein: Progesterone (MAIN) and Estradiol-17B

Granulosa Lutein: Androstenedione

37
Q

What is going to happen to Basal Body Temperature during the Luteal Phase?

A

Progesterone is going to be responsible for an INCREASE in the Basal Body Temperature!

If Pregnancy does not occur, you are going to have degeneration of the CORPUS Luteum which will DECREASE the basal body temperature back down to normal at the END of the Luteal Phase

38
Q

What is going to happen to Basal Body Temperature during the Follicular Phase?

A

Estrogen is going to be responsible for a DECREASE in Basal Body Temperature

39
Q

When is the endometrium going to be restored during the Proliferative Phase? Which hormone is responsible for the proliferation and differentiate of the Endometrium?

A

5th Day of the Cycle

ESTROGEN

40
Q

What is the function of progesterone during the Proliferative Phase?

A

Stimulates 17B-HSD and Sulfotransferase to convert ESTRADIOL to Weaker compounds

INHIBITS epithelial cell proliferation but PROMOTES proliferation of the endometrial STROMA

41
Q

Which hormone is crucial to the Secretory Phase?

A

Progesterone

42
Q

Increases in vascularization of the endometrium and glycogen content is stimulate by which hormone during the Secretory Phase?

A

ESTROGEN

43
Q

When are you going to take the different type of Oral Contraceptive Pills?

A

1- 21 Days: Oral Contraceptive Pill

22-28 Days: Placebo Pill

44
Q

Explain how Oral Contraceptive Pills work in regards to the HPA axis.

A
  • Negative Feedback on the Hypothalamus and Anterior Pituitary
  • Low FSH levels are insufficient to stimulate normal Folliculogenesis
  • Low LH levels will inhibit Ovulation
45
Q

How does the Progestin-Only Contraceptive work?

A
  • Causes Cervical Mucus to thicken and become sticky, making it difficult for the Spermatozoa to penetrate.
  • You will still have Ovulation
46
Q

Define: Menorrhagia, Dysmenorrhea, Oligomenorrhea, and Amenorrhea

A

Menorrhagia: Loss of > 80 mL of Blood

Dysmenorrhea: PAINFUL Periods

Oligomenorrhea: Existence of few, irregular periods

Amenorrhea: ABSENCE of periods

47
Q

Describe the Pathophysiology of Polycystic Ovarian Syndrome.

A
  • Overproduction of Androgens (DHEA)
  • Causes growing follicles that are not Ovulated and you get cyst formation in the Ovaries
  • Risk Factors: Obesity and Diabetes Mellitus
  • ELEVATED (LH and Testosterone) & LOW (FSH)
48
Q

Describe the Clinical Presentation of Turner’s Syndrome.

A
  • Female Phenotype
  • Webbed Neck
  • Square Chest
  • Short Stature
  • 45 XO
49
Q

Describe the Pathophysiology of Turner’s Syndrome.

A
  • Primary Hypogonadism
  • Ovarian Failure
  • Feedback mechanisms are absent so you are going to have HIGH FSH and LH levels in the serum
50
Q

Describe hormonal changes that occur with Menopause.

A
  • Occurs around 51 years of age
  • Due to REDUCTION in ESTROGEN and LOW levels of INHIBIN
  • HIGH LEVELS of LH and FSH due to NO negative Feedback mechanisms