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Gynaecology > Ovarian and Menstrual Cycle > Flashcards

Ovarian and Menstrual Cycle Flashcards

1
Q

What are the hormones secreted by the anterior pituitary?

A

The anterior pituitary secretes six hormones: Growth Hormone (GH), Prolactin (PRL), Thyroid-Stimulating Hormone (TSH), Adrenocorticotropic Hormone (ACTH), Follicle-Stimulating Hormone (FSH), and Luteinizing Hormone (LH).

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2
Q

What stimulates the release of Growth Hormone (GH)?

A

Growth Hormone-Releasing Hormone (GHRH) from the hypothalamus stimulates its release. GH release is inhibited by Somatostatin (GHIH).

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3
Q

What is the primary target of Growth Hormone (GH), and what are its effects?

A

GH primarily targets the liver and various tissues. It stimulates the production of insulin-like growth factor 1 (IGF-1), promotes growth of bones and muscles, and increases protein synthesis and fat metabolism.

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4
Q

What stimulates the release of Prolactin (PRL)?

A

Prolactin-Releasing Factors (PRFs) from the hypothalamus and a decrease in dopamine (Prolactin-Inhibiting Factor, PIF) stimulate its release.

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5
Q

What is the primary target of Prolactin (PRL), and what are its effects?

A

PRL targets the mammary glands to stimulate milk production during lactation.

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6
Q

What stimulates the release of Thyroid-Stimulating Hormone (TSH)?

A

Thyrotropin-Releasing Hormone (TRH) from the hypothalamus stimulates TSH release.

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7
Q

What is the primary target of TSH, and what are its effects?

A

TSH targets the thyroid gland, stimulating the synthesis and release of thyroid hormones (T3 and T4), which regulate metabolism.

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8
Q

What stimulates the release of Adrenocorticotropic Hormone (ACTH)?

A

Corticotropin-Releasing Hormone (CRH) from the hypothalamus stimulates ACTH release.

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9
Q

What is the primary target of ACTH, and what are its effects?

A

ACTH targets the adrenal cortex, stimulating the production of glucocorticoids (like cortisol), which are involved in stress responses, metabolism, and immune function.

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10
Q

What stimulates the release of Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH)?

A

Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus stimulates the release of FSH and LH.

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11
Q

What are the primary targets and effects of FSH?

A

In females: FSH targets the ovaries, promoting follicle development and estrogen production.

In males: FSH targets the testes, stimulating spermatogenesis.

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12
Q

What are the primary targets and effects of LH?

A

In females: LH targets the ovaries, triggering ovulation and stimulating progesterone production.

In males: LH targets the testes, stimulating testosterone production.

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13
Q

How are anterior pituitary hormones regulated?

A

Anterior pituitary hormones are regulated by releasing and inhibiting hormones from the hypothalamus and feedback loops involving the hormones produced by their target glands.

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14
Q

What are the hormones secreted by the posterior pituitary?

A

The posterior pituitary secretes two hormones: Antidiuretic Hormone (ADH) (also known as Vasopressin) and Oxytocin.

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15
Q

Where are posterior pituitary hormones synthesized?

A

They are synthesized in the hypothalamus:

  • ADH is produced by the supraoptic nucleus.
  • Oxytocin is produced by the paraventricular nucleus.
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16
Q

How do the hormones reach the posterior pituitary for release?

A

ADH and Oxytocin are transported down axons of the hypothalamic-hypophyseal tract and stored in the posterior pituitary until release

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17
Q

What stimulates the release of Antidiuretic Hormone (ADH)?

A

ADH is released in response to:

  • Increased plasma osmolality (detected by osmoreceptors in the hypothalamus).
  • Decreased blood volume or pressure (detected by baroreceptors).
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18
Q

What are the primary targets of ADH, and what are its effects?

A

Target: The kidneys (collecting ducts).

Effect: Promotes water reabsorption by increasing the permeability of the collecting ducts, which concentrates the urine and maintains water balance.

Additional Effect: In high concentrations, ADH causes vasoconstriction, increasing blood pressure.

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19
Q

What stimulates the release of Oxytocin?

A

Oxytocin is released in response to:

  • Stretching of the cervix and uterus during labor.
  • Suckling of the nipple during breastfeeding.
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20
Q

What are the primary targets of Oxytocin, and what are its effects?

A

Target: Uterus and mammary glands.

Effects:
- Stimulates uterine contractions during labor (positive feedback mechanism).
- Promotes milk ejection (“let-down reflex”) during breastfeeding.

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21
Q

How are posterior pituitary hormones regulated?

A

ADH: Regulated by osmoreceptors and baroreceptors in response to fluid and electrolyte balance.

Oxytocin: Regulated by positive feedback mechanisms, especially during childbirth and lactation.

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22
Q

What is a clinical condition associated with insufficient ADH?

A

Diabetes Insipidus: Characterized by excessive urination (polyuria) and thirst (polydipsia) due to a lack of ADH or kidney insensitivity to ADH.

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23
Q

What is a clinical condition associated with excessive ADH?

A

Syndrome of Inappropriate ADH Secretion (SIADH): Characterized by water retention, hyponatremia, and reduced urine output due to excessive ADH secretion.

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24
Q

What characterizes the reproductive cycle in women?

A

The reproductive cycle is a dynamic system with short-term hormonal fluctuations (minute-to-minute), leading to changing morphological and functional states characteristic of the normal ovarian cycle.

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25
Q

What conditions are necessary for ovulatory cycles to occur?

A

Ovulatory cycles require:

  1. An intact CNS-hypothalamic-pituitary-ovarian (HPO) axis.
  2. A responsive endometrium.
  3. A patent outflow tract.
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26
Q

What marks the onset of the hypothalamo-pituitary-ovarian (HPO) axis functionality?

A

Events around the onset of puberty, including:

  • Thelarche: Development of breasts.
  • Adrenarche: Onset of adrenal androgen production.
  • Menarche: The first menstrual cycle.
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27
Q

What marks the decline in the HPO axis functionality?

A

The decline is represented by:

  1. Perimenopause: The transition phase leading to menopause.
  2. Menopause: The cessation of menstruation and end of reproductive capability.
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28
Q

What characterizes a functional HPO axis between puberty and menopause?

A

A functional HPO axis is represented by regular cyclical menses and the potential for fertility.

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29
Q

How do external and internal environments influence reproduction?

A

External environment: Factors like nutrition, light, and seasons affect reproduction.

Internal environment: Factors like body fuel availability and psychological status are critical.

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30
Q

What is the hypothalamus’s role in linking the environment to reproduction?

A

The hypothalamus integrates environmental signals to regulate reproductive function, ensuring conditions are conducive for potential pregnancy and offspring.

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31
Q

What is the Hypothalamus-Pituitary-Ovarian (HPO) axis?

A

The HPO axis is a hormonal feedback system that regulates female reproduction, including ovulation, menstrual cycles, and fertility.

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32
Q

What hormones are involved in the HPO axis?

A

Hypothalamus: Gonadotropin-Releasing Hormone (GnRH).

Pituitary: Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH).

Ovaries: Estrogen, Progesterone, and Inhibin.

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33
Q

What is the role of the hypothalamus in the HPO axis?

A

The hypothalamus secretes GnRH in a pulsatile manner to stimulate the anterior pituitary to release FSH and LH.

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34
Q

What is the role of the anterior pituitary in the HPO axis?

A

FSH: Stimulates follicular growth and estrogen production in the ovaries.

LH: Triggers ovulation and stimulates progesterone production by the corpus luteum.

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35
Q

What is the role of the ovaries in the HPO axis?

A

Produce estrogen and progesterone to regulate the endometrial cycle and feedback to the hypothalamus and pituitary.

Secrete inhibin to selectively inhibit FSH release.

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36
Q

How does feedback regulation occur in the HPO axis?

A

Negative feedback: High levels of estrogen and progesterone inhibit GnRH, FSH, and LH secretion.

Positive feedback: During the late follicular phase, high estrogen levels stimulate a surge in GnRH and LH, leading to ovulation.

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37
Q

What happens during the follicular phase of the menstrual cycle in the HPO axis?

A

GnRH: Stimulates FSH and LH secretion.

FSH: Promotes follicle development and estrogen production.

Estrogen: Thickens the endometrium and provides negative feedback to reduce FSH secretion.

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38
Q

What triggers ovulation in the HPO axis?

A

A surge in LH, caused by positive feedback from high estrogen levels, triggers ovulation (release of the mature egg).

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39
Q

What happens during the luteal phase in the HPO axis?

A

The corpus luteum forms and secretes progesterone and estrogen.

Progesterone prepares the endometrium for implantation and exerts negative feedback on GnRH, FSH, and LH.

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40
Q

What happens if fertilization does not occur in the HPO axis?

A

The corpus luteum degenerates, leading to a drop in progesterone and estrogen.

The drop removes negative feedback, allowing GnRH, FSH, and LH secretion to restart the cycle.

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41
Q

How is the HPO axis affected by external factors?

A

Stress, malnutrition, or excessive exercise: Can suppress GnRH release, disrupting the cycle.

Polycystic Ovary Syndrome (PCOS): Leads to abnormal feedback and hormone imbalances.

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42
Q

How does menopause affect the HPO axis?

A

Ovaries become unresponsive to FSH and LH, leading to low estrogen and progesterone levels.

FSH and LH levels rise due to the loss of negative feedback.

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43
Q

What are the three phases of the ovarian cycle?

A
  1. Follicular phase.
  2. Ovulation.
  3. Luteal phase.
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44
Q

What is the primordial follicle, and what phase of meiosis is the oocyte in?

A

The primordial follicle consists of an oocyte arrested in the prophase of the first meiotic division, surrounded by granulosa cells.

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45
Q

How is the growth of primordial follicles initiated?

A

Growth begins independently of gonadotropins (Gn-independent).

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46
Q

What hormonal changes mark the follicular phase?

A

Decreased luteal steroidogenesis and inhibin secretion.

Increased FSH levels.

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47
Q

What happens during follicular recruitment?

A

A cohort of follicles is recruited, and one follicle is selected for dominance.

48
Q

How does the dominant follicle survive despite decreasing FSH levels?

A

The dominant follicle has:

  • Increased FSH receptor content.
  • Autocrine/paracrine peptides.
  • Enhanced vasculature, allowing it to respond to lower FSH levels.
49
Q

What changes occur in granulosa cells of the dominant follicle?

A

FSH induces LH receptors on granulosa cells, which is coordinated by local auto- and paracrine factors.

50
Q

How does the dominant follicle control its own development?

A

Through its production of estrogen and peptides.

51
Q

What triggers the LH surge in the late follicular phase?

A

Positive feedback from increasing estrogen levels alters GnRH pulsing, resulting in the LH surge.

52
Q

What event induces ovulation?

A

The LH surge, which occurs about 10-12 hours before ovulation and 24-36 hours after the estradiol peak.

53
Q

What key events does the LH surge stimulate?

A
  • Resumption of meiosis in the oocyte.
  • Progressive rise in granulosa cell progesterone production.
  • Activation of proteolytic enzymes to break down follicular wall collagen.
  • Increase in follicular prostaglandin production.
  • Luteinization of granulosa cells.
  • Progesterone-influenced midcycle FSH rise.
  • Induction of LH receptors for an adequate luteal phase.
54
Q

What is the role of androgens during ovulation?

A

Androgens rise midcycle, produced by theca cells of follicles that were recruited but not selected (underwent apoptosis).

55
Q

What hormone suppresses new follicular growth in the luteal phase?

A

Progesterone

56
Q

When do progesterone levels peak in the luteal phase?

A

Approximately 8 days after the LH surge.

57
Q

What maintains luteal function if conception occurs?

A

hCG (human chorionic gonadotropin) until placental steroidogenesis is established.

58
Q

What happens to the corpus luteum if conception does not occur?

A

It is maintained by LH but declines 9-11 days after ovulation. Menses occur about 14 days after ovulation.

59
Q

What mechanisms are thought to cause regression of the corpus luteum?

A

Local prostaglandin production.

Luteolytic action of its own estrogens

60
Q

What regulates the ovarian cycle?

A

The ovarian cycle is regulated by steroid hormones (estrogen and progesterone) and autocrine/paracrine peptides acting on ovarian follicles.

61
Q

What ensures a coordinated ovarian cycle?

A

The interplay between the hypothalamus, pituitary, and ovaries through the release of GnRH, FSH, LH, estrogen, and progesterone.

62
Q

What marks the transition from primordial follicles to pre-antral follicles?

A

Recruitment of primordial follicles during the first days of the cycle.

Transition to pre-antral stage occurs when growth becomes gonadotropin-dependent, accompanied by estrogen production.

63
Q

What is the significance of FSH during the early follicular phase?

A

FSH stimulates follicular development and granulosa cell proliferation, increasing estrogen secretion.

64
Q

How does the selection of a dominant follicle occur?

A

Among the recruited cohort, the follicle with the highest FSH receptor content and superior vascular supply is selected for dominance, while others undergo atresia.

65
Q

What effect does estrogen have on the hypothalamus and pituitary during the follicular phase?

A

Early phase: Negative feedback reduces FSH secretion.

Late phase: Positive feedback triggers the LH surge.

66
Q

What structural changes occur in the dominant follicle?

A

The dominant follicle enlarges, its granulosa cells proliferate, and it begins producing large amounts of estrogen.

67
Q

What enzymes are activated during ovulation?

A

Proteolytic enzymes are activated to break down the collagen in the follicular wall, facilitating oocyte release.

68
Q

What triggers the oocyte to resume meiosis?

A

The LH surge signals the oocyte to resume meiosis, progressing to metaphase II before ovulation.

69
Q

What role do prostaglandins play in ovulation?

A

Prostaglandins increase within the follicle to aid follicular rupture and oocyte release.

70
Q

How long after the LH surge does ovulation occur?

A

Ovulation occurs approximately 24-36 hours after the estradiol peak and 10-12 hours after the LH peak.

71
Q

What structural feature supports oocyte release?

A

The stigma (a weakened spot on the follicle wall) ruptures, allowing the oocyte to exit the follicle.

72
Q

What happens to the granulosa and theca cells post-ovulation?

A

They luteinize (transform into luteal cells) and form the corpus luteum, which secretes progesterone and estrogen.

73
Q

Why is progesterone important during the luteal phase?

A

Progesterone stabilizes the endometrium, preparing it for implantation if fertilization occurs.

74
Q

What is the lifespan of the corpus luteum in a non-conception cycle?

A

The corpus luteum degenerates after 9-11 days, leading to a drop in progesterone and the onset of menstruation.

75
Q

What maintains the corpus luteum in a conception cycle?

A

hCG from the developing embryo maintains the corpus luteum until the placenta takes over hormone production.

76
Q

What causes the decline of the corpus luteum in a non-conception cycle?

A

Declining LH levels, local prostaglandin production, and possible luteolytic effects of estrogens contribute to its regression.

77
Q

How does the luteal phase ensure synchrony with the uterine cycle?

A

The peak in progesterone secretion corresponds with the secretory phase of the endometrium, preparing it for potential implantation.

78
Q

What is the average length of the menstrual cycle?

A

The average interval is 25-35 days.

79
Q

How long does menstrual flow typically last?

A

Menstrual flow lasts 3-6 days.

80
Q

What is the average blood loss during menstruation?

A

Average blood loss is 30-80 mL.

81
Q

How is a “regular” menstrual cycle defined?

A

A regular cycle has:

  • A minimum inter-menstrual interval of 21 days.
  • A maximum interval of 35 days.
  • An inter-cycle variation of ≤4 days for an individual.
82
Q

What is an alternate definition of cycle regularity?

A

Cycle-to-cycle variation of ≤7 days (≤9 days at age extremes).

83
Q

What determines the length of the menstrual cycle?

A

The length of the follicular phase is the major determinant of cycle length.

84
Q

What happens to the endometrium during the follicular phase?

A

Under the influence of estrogen, the endometrium grows from 0.5 mm to 3.5-5.0 mm in height, becoming proliferative.

85
Q

At what ages are anovulatory cycles most common?

A

Anovulatory cycles occur most commonly under 20 years and over 40 years.

86
Q

Why do anovulatory cycles occur at these ages?

A

These age extremes represent periods when the hypothalamo-pituitary-ovarian (HPO) axis may be immature (in younger women) or declining (in older women).

87
Q

What happens to the endometrium after ovulation?

A

Combined estrogen and progesterone secretion results in the development of the compact secretory endometrium.

88
Q

How does the endometrium prepare for potential implantation?

A

The secretory phase produces a mature, glandular endometrium conducive to embryo implantation.

89
Q

What triggers menstruation if fertilization does not occur?

A

Falling concentrations of estrogen and progesterone lead to:

  • Release of liposomal enzymes.
  • A chain of events culminating in the shedding of the endometrium (menstruation).
90
Q

What happens to the endometrium during menstruation?

A

The compact and functional layers are shed, leaving the basal layer intact.

91
Q

How does ovarian steroidogenesis influence the endometrium?

A
  • Estrogens promote proliferation during the follicular phase.
  • Combined estrogen and progesterone stabilize and mature the endometrium in the luteal phase.
92
Q

What is the maximum acceptable inter-menstrual interval for a “regular” cycle?

A

35 days.

93
Q

What is the minimum inter-menstrual interval for a “regular” cycle?

A

21 days.

94
Q

What is the significance of inter-cycle variation?

A

For regular cycles, the inter-cycle variation should not exceed 4 days in an individual.

95
Q

What hormone drives the changes in the endometrium during the follicular phase?

A

Estrogens

96
Q

How thick does the endometrium grow during the follicular phase?

A

It grows from approximately 0.5 mm to 3.5-5.0 mm in height.

97
Q

What is the state of the endometrium during the follicular phase?

A

The endometrium is in a proliferative state.

98
Q

What marks the transition from the follicular phase to the luteal phase?

A

Ovulation, triggered by the LH surge.

99
Q

What hormones are responsible for the secretory changes in the endometrium after ovulation?

A

Combined effects of estrogen and progesterone.

100
Q

What happens to the endometrium during the secretory phase?

A

The endometrium becomes compact, glandular, and prepared for potential embryo implantation.

101
Q

What causes the shedding of the endometrium in the absence of fertilization?

A

Falling concentrations of estrogen and progesterone.

102
Q

What role do liposomal enzymes play in menstruation?

A

Liposomal enzymes initiate a chain of events that lead to the breakdown and shedding of the functional layer of the endometrium.

103
Q

Which layer of the endometrium remains intact after menstruation?

A

The basal layer.

104
Q

How do anovulatory cycles differ from ovulatory cycles?

A

Anovulatory cycles lack ovulation, meaning there is no LH surge, corpus luteum formation, or progesterone production.

105
Q

How does an anovulatory cycle affect the endometrium?

A

The endometrium remains under estrogen stimulation without the stabilizing effects of progesterone, which may lead to irregular or heavy bleeding.

106
Q

What is the most common cause of anovulatory cycles at age extremes?

A

Immaturity or decline in the hypothalamo-pituitary-ovarian (HPO) axis.

107
Q

What are the three phases of the uterine cycle?

A
  1. Menstrual phase
    Proliferative phase
    Secretory phase
108
Q

What occurs during the menstrual phase of the uterine cycle?

A

The functional layer of the endometrium is shed, resulting in menstrual bleeding.

109
Q

What triggers the menstrual phase?

A

A drop in estrogen and progesterone levels due to regression of the corpus luteum.

110
Q

How long does the menstrual phase typically last?

A

It lasts 3-6 days.

111
Q

What part of the endometrium remains intact after menstruation?

A

The basal layer.

112
Q

What drives the proliferative phase of the uterine cycle?

A

Rising estrogen levels from developing ovarian follicles.

113
Q

What happens to the endometrium during the proliferative phase?

A

The endometrium regenerates and thickens, growing from about 0.5 mm to 3.5-5 mm.

114
Q

What structural changes occur in the endometrium during the proliferative phase?

A

Endometrial glands elongate and spiral arteries begin to form.

115
Q
A
116
Q
A

Gynaecology (1 decks)

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