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OBG: Functional Gynaecology > Hormonal and endometrial changes in menstrual cycle > Flashcards

Hormonal and endometrial changes in menstrual cycle Flashcards

1
Q

What is the average duration of the menstrual cycle?

A

28 days

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2
Q

What are the 3 phases of the menstrual cycle?

A

Follicular phase, ovulation, post-ovulatory/ secretory (or luteal) phase

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3
Q

What happens during the follicular/proliferative phase of the menstrual cycle?

A

Endometrium thickens

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4
Q

What happens during the secretory/ luteal phase of the menstrual cycle?

A

after ovulation, endometrial growth stops and the endometrial glands become active and full of secretions

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5
Q

What changes to the 3 phases of the menstrual cycle occur if the cycle is prolonged and what ALWAYS stays the same?

A

if the cycle is prolonged, the follicular phase lengthens (longer time to ovulation) but the luteal phase remains constant

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6
Q

What is the length of the luteal phase of the menstrual cycle?

A

ALWAYS 14 days

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7
Q

What 3 things are fundamental to the normal menstrual cycle?

A
  1. Intact hypothalamo-pituitary-ovarian endocrine axis
  2. Presence of responsive follicles in the ovaries
  3. Functional uterus
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8
Q

Despite the hypothalamus controlling the menstrual cycle, what in turn can influence the hypothalamus?

A

high centres in the brain, so factors such as anxiety or stress can affect the cycle

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9
Q

What is the role of the hypothalamus and pituitary gland in the control of the menstrual cycle?

A
  • Hypothalamus secretes gonadotrophin-releasing hormone (GnRH)
  • GnRH travells through small blood vessels of pituitary portal system to the anterior pituitary
  • GnRH acts on pituitary gonadotrophs to stimulate the synthesis and release of follicle-stimulating hormone (FSH) and luteinising hormone (LH)
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10
Q

What is gonadotrophin-releasing hormone and how often is it released?

A

decapeptide, secreted in a pulsatile manner approximately every 90 minutes

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11
Q

What are the effects of secretion of FSH and LH by the anterior pituitary gland on the hypothalamus?

A

Negative feedback effect

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12
Q

What are the 2 key roles of FSH?

A
  1. stimulates growth of follicles during follicular phase of the cycle
  2. also stimulates sex hormone secretion, predominantly of oestradiol, by the granulosa cells of the mature ovarian follicle
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13
Q

What type of molecule are both FSH and LH?

A

glycoprotein

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14
Q

What are 3 key roles of LH?

A
  1. Stimulates sex hormone production - mainly testosterone, subsequently converted by FSH into oestradiol
  2. Mid-cycle surge of LH triggers rupture of mature follicle with release of oocyte
  3. Influences post-ovulatory production of progesterone by corpus luteum
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15
Q

What helps to maintain the cyclical activity within the ovary which constitutes the ovarian cycle?

A

feedback mechanisms between ovary, hypothalamus and pituitary

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16
Q

What happens to FSH and LH levels at the start of the cycle (follicular phase, days 1-8) and what triggers this?

A

levels of FSH and LH levels rise in repsonse to fall of oestradiol and progesterone at menstruation

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17
Q

What happens as a result of the rise in LH and FSH at the start of the cycle - follicular phase, days 1-8?

A
  • the rise in FSH and LH stimulates development of 10-20 follicles
  • the follicle that is most sensitive to FSH is the dominant follicle and is the one destined to reach full maturation and ovulation
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18
Q

At what point does the dominant follicle appear in the menstrual cycle and what happens to the remaining follicles that developed following a rise in FSH and LH?

A
  • this appears during the mid-follicular phase
  • the remainder undergo atresia
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19
Q

What happens to hormone levels in association with growth of the dominant follicle in the mid-follicular phase?

A

Oestradiol levels increase

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20
Q

Describe the development of the dominant follicle? 3 stages

A
  1. primary follicle increases in size and localised accumulations of fluid appear among the granulosa cells and become confluent
  2. confluence gives rise to fluid-filled central cavity called the antrum, which transforms primary follicle into a Graafian follicle
  3. the oocyte occupies an eccentric position in the Graafian follicle, surrounded by two to three layers of granulosa cells termed the cumulus oophorus
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21
Q

Describe the position of the oocyte in the Graafian follicle.

A

Eccentric position, surrounded by two to three layers of granulosa cells termed the cumulus oophorus

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22
Q

When does development of the dominant follicle into a Graafian follicle occur?

A

Days 9-14 (follicular phase)

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23
Q

What happens to hormone levels as the follicle matures and what secretes the hormone?

A
  • Progressive increase in production of oestrogen (mainly oestradiol) by the granulosa cells of the developing follicle
  • Granulosa cells also produce inhibin
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24
Q

What is the effect of the release of oestradiol by the developing follicle during the follicular phase?

A

negative feedback to suppress gonadotrophins, preventing hyperstimulation of the ovary and maturation of multiple follicles

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25
Q

What is the effect of inhibin, produced by the granulosa cells?

A

Implicated as a factor in the restriction of number of follicles undergoing maturation

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26
Q

When does ovulation occur?

A

Day 14

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27
Q

What happens at ovulation?

A

Rapid enlargement of the follicle followed by protrusion from the surface of the ovarian cortex and rupture of the follicle, with extrusion of the oocyte and adherent cumulus oophorus

28
Q

What is the word used to describe pain experienced just before follicular rupture at ovulation?

A

Mittelschmerz: short-lived pain in one or other iliac fossa

29
Q

What is believed to be the effect of the final rise in oestradiol concentration just before ovulation? What happens to the oestradiol and progesterone levels after this?

A
  • responsible for mid-cycle surge of LH and, to a lesser extent, of FSH
  • Immediately before ovulation there is a precipitous fall in oestradiol levels and increase in progesterone production
30
Q

Within what time frame following the mid-cycle surge of LH does ovulation occur?

A

follows within 18 hours of the surge

31
Q

What happens to the Graafian follicle during the luteal phase (days 15-28)?

A
  • it is retained in the ovary and penetrated by capillaries and fibroblasts from the theca
  • granulosa cells undergo luteinisation and collectively form the corpus luteum
32
Q

What is the role of the corpus luteum, formed in the luteal phase?

A

major source of sex steroid hormones oestradiol and progesterone which are secreted by the ovary in the post-ovulatory phase

33
Q

What is the result of establishment of the corpus luteum?

A

marked increase in progesterone secretion, second rise in oestradiol levels

34
Q

At what point in the ovarian cycle do progesterone levels peak and what is a use for this?

A
  • peak 1 week after ovulation (day 21) after formation of corpus luteum
  • Tests of serum progesterone at this time may be used in fertility investigations to confirm occurrence of ovulation
35
Q

What happens to gonadotrophin levels during the luteal phase?

A

Reach the lowest point; remain low until regression of corpus luteum, which occurs at days 26-28

36
Q

At what point in the menstrual cycle does regression of the corpus luteum occur?

A

days 26-28 - only if conception and implantation don’t occur

37
Q

What happens to the corpus luteum if conception and implantation occurs and why?

A

the corpus luteum does not regress because it is maintained by human chorionic gonadotrophin (hCG) secreted by the trophoblast

38
Q

What happens following regression of the corpus luteum?

A
  1. Progesterone levels fall, menstruation ensues
  2. Consequent fall in sex hormones allows FSH and LH levels to rise and initiate the next cycle
39
Q

What are the 2 things that change in the uterus due to the cyclical production of sex hormones by the ovary?

A

Endometrial changes and changes in cervical mucus

40
Q

What is the anatomy of the endometrium?

A
  • Consists of two layers:
    • superficial layer that is shed in course of menstruation
    • basal layer, does not take part in shedding but regenerates the superficial layer during the subsequent cycle
  • junction between 2 layers
41
Q

What marks the junction between the basal and superficial layers of the endometrium?

A

change in the arterioles that supply it; portion of arterioles in the basal endometrium is straight but in the superficial layer their course becomes convoluted, giving rise to the spiral section of the arteriole

42
Q

What are the 3 phases of the menstrual cycle referred to when discussing the endometrium?

A
  1. Proliferative phase
  2. Secretory phase
  3. Menstrual phase
43
Q

What happens during the proliferative phase in the endometrium? 3 points

A
  1. during the follicular phase in the ovary, the endometrium is exposed to oestrogen
  2. after menstruation, secretion of oestradiol from ovary brings about repair and regeneration of endometrium
  3. ongoing growth and proliferation of glands and blood vessels.
44
Q

What is the arrangement of the glands in the endometrium during the proliferative phase?

A

the glands are tubular and arranged in a regular pattern, parallel to each other

45
Q

What happens to the endometrium during the secretory phase?

A
  • after ovulation, progesterone production induces secretory changes in the endometrial glands, preparing the endometrium for implantation
  • secretory vacuoles in the glandular epithelium appear below the nuclei
  • progresses to secretion of material into the lumen of the glands, which become tortuous and their margins appear serrated
46
Q

What happens to the endometrium during the menstrual phase?

A
  1. Regression of corpus luteum associated with decline in ovarian oestradiol and progesterone production
  2. followed by intense spasmodic contraction of spiral section of endometrial arterioles, giving rise to ischaemic necrosis, shedding of superficial layer of endometrium and bleeding
47
Q

What triggers the vasospasm of the spiral section of endometrial arterioles leading to shedding of the superficial layer?

A

appears to be due to local production of prostaglandins

48
Q

What do prostaglandins that cause spiral arteriole sections to spasmodically contract also possibly cause?

A

increased uterine contractions at time of menstrual blood flow

49
Q

What is thought to be the reason for failure of menstrual blood to clot?

A

Presence of local fibrinolytic activity in the endometrial blood vessels, which reaches a peak at the time of menstruation

50
Q

What produces the cervical mucus?

A

glands of the cervix

51
Q

What causes the differences in the type of cervical mucus produced at different points in the cycle?

A

sex hormones from the ovary

52
Q

What is cervical mucus like early in the follicular phase?

A

cervical mucus is scant

53
Q

What changes happen to cervical mucus later in the follicular phase?

A
  • increasing oestradiol levels induce changes in composition, making it more stretchy - change called ‘spinnbarkheit’.
  • Water content increases progressively so just before ovulation mucus is watery and easily penetrated by spermatozoa
54
Q

What does mid-cycle cervical mucus look like under the microscope?

A

Characteristic fern-like pattern

55
Q

What is mucus like after ovulation (secretory phase)?

A
  • progesterone secreted by corpus luteum counters effect of oestradiol, so mucus becomes thick and impermeable
  • prevents entry of further spermatozoa
56
Q

How can the effects of progesterone on mucus explain one way that progestogen-only methods of contrcaeption exert their contraceptive effect?

A

after ovulation, high progesterone levels causes thick impermeale mucus to prevent entry of further spermatozoa

57
Q

When might a woman want to monitor changes in cervical mucus?

A

if using rhythm method of contraception

58
Q

What are 3 additional cyclical changes outside of the genital tract due to ovarian hormones?

A
  1. Basal body temperature
  2. Breast changes
  3. Psychological changes
59
Q

What changes to basal body temperature occur with cyclical hormonal changes?

A

rise of basal body temperature of approximately 0.5oC following ovulation and is sustained until onset of menstruation

60
Q

What causes the rise in body temperature between ovulation and menstruation?

A

thermogenic effect of progesterone acting at the hypothalamic level

61
Q

What happens to the rise in body temperature in pregnancy?

A

if conception occurs, elevation in basal body temperature at ovulation is maintained throughout pregnancy

62
Q

What can mimic the effect of progesterone between ovulation and menstruation?

A

administration of progestogens

63
Q

What is often the first sign of puberty and why?

A

breast swelling, in response to the small increase in ovarian oestrogens as human mammary gland is very sensitive to oestrogen and progesterone

64
Q

How do hormones in the body act on the breast tissue?

A

Oestradiol and progesterone act synergistically on the breast

65
Q

What breast changes happen during the normal menstrual cycle? What is this due to?

A

Breast swelling occurs in the luteal (secretory) phase apparently in response to increasing progesterone levels

swelling likely due to vascular changes (not changes in glandular tissue)

66
Q

What psychological changes have been reported in association with the menstrual cycle?

A

increase in emotional lability in the late luteal phase

67
Q

What is thought to cause mood changes in the menstrual cycle?

A

falling levels of progesterone - but not always closely synchronised with hormonal fluctuations

OBG: Functional Gynaecology (7 decks)

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