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Gynaecology > 1. Ovarian and Menstrual Cycle > Flashcards

1. Ovarian and Menstrual Cycle Flashcards

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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
What conditions are necessary for ovulatory cycles to occur?
Ovulatory cycles require: 1. An intact CNS-hypothalamic-pituitary-ovarian (HPO) axis. 2. A responsive endometrium. 3. A patent outflow tract.
26
What marks the onset of the hypothalamo-pituitary-ovarian (HPO) axis functionality?
Events around the onset of puberty, including: - Thelarche: Development of breasts. - Adrenarche: Onset of adrenal androgen production. - Menarche: The first menstrual cycle.
27
What marks the decline in the HPO axis functionality?
The decline is represented by: 1. Perimenopause: The transition phase leading to menopause. 2. Menopause: The cessation of menstruation and end of reproductive capability.
28
What characterizes a functional HPO axis between puberty and menopause?
A functional HPO axis is represented by regular cyclical menses and the potential for fertility.
29
How do external and internal environments influence reproduction?
External environment: Factors like nutrition, light, and seasons affect reproduction. Internal environment: Factors like body fuel availability and psychological status are critical.
30
What is the hypothalamus's role in linking the environment to reproduction?
The hypothalamus integrates environmental signals to regulate reproductive function, ensuring conditions are conducive for potential pregnancy and offspring.
31
What is the Hypothalamus-Pituitary-Ovarian (HPO) axis?
The HPO axis is a hormonal feedback system that regulates female reproduction, including ovulation, menstrual cycles, and fertility.
32
What hormones are involved in the HPO axis?
Hypothalamus: Gonadotropin-Releasing Hormone (GnRH). Pituitary: Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH). Ovaries: Estrogen, Progesterone, and Inhibin.
33
What is the role of the hypothalamus in the HPO axis?
The hypothalamus secretes GnRH in a pulsatile manner to stimulate the anterior pituitary to release FSH and LH.
34
What is the role of the anterior pituitary in the HPO axis?
FSH: Stimulates follicular growth and estrogen production in the ovaries. LH: Triggers ovulation and stimulates progesterone production by the corpus luteum.
35
What is the role of the ovaries in the HPO axis?
Produce estrogen and progesterone to regulate the endometrial cycle and feedback to the hypothalamus and pituitary. Secrete inhibin to selectively inhibit FSH release.
36
How does feedback regulation occur in the HPO axis?
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.
37
What happens during the follicular phase of the menstrual cycle in the HPO axis?
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.
38
What triggers ovulation in the HPO axis?
A surge in LH, caused by positive feedback from high estrogen levels, triggers ovulation (release of the mature egg).
39
What happens during the luteal phase in the HPO axis?
The corpus luteum forms and secretes progesterone and estrogen. Progesterone prepares the endometrium for implantation and exerts negative feedback on GnRH, FSH, and LH.
40
What happens if fertilization does not occur in the HPO axis?
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.
41
How is the HPO axis affected by external factors?
Stress, malnutrition, or excessive exercise: Can suppress GnRH release, disrupting the cycle. Polycystic Ovary Syndrome (PCOS): Leads to abnormal feedback and hormone imbalances.
42
How does menopause affect the HPO axis?
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.
43
What are the three phases of the ovarian cycle?
1. Follicular phase. 2. Ovulation. 3. Luteal phase.
44
What is the primordial follicle, and what phase of meiosis is the oocyte in?
The primordial follicle consists of an oocyte arrested in the prophase of the first meiotic division, surrounded by granulosa cells.
45
How is the growth of primordial follicles initiated?
Growth begins independently of gonadotropins (Gn-independent).
46
What hormonal changes mark the follicular phase?
Decreased luteal steroidogenesis and inhibin secretion. Increased FSH levels.
47
What happens during follicular recruitment?
A cohort of follicles is recruited, and one follicle is selected for dominance.
48
How does the dominant follicle survive despite decreasing FSH levels?
The dominant follicle has: - Increased FSH receptor content. - Autocrine/paracrine peptides. - Enhanced vasculature, allowing it to respond to lower FSH levels.
49
What changes occur in granulosa cells of the dominant follicle?
FSH induces LH receptors on granulosa cells, which is coordinated by local auto- and paracrine factors.
50
How does the dominant follicle control its own development?
Through its production of estrogen and peptides.
51
What triggers the LH surge in the late follicular phase?
Positive feedback from increasing estrogen levels alters GnRH pulsing, resulting in the LH surge.
52
What event induces ovulation?
The LH surge, which occurs about 10-12 hours before ovulation and 24-36 hours after the estradiol peak.
53
What key events does the LH surge stimulate?
- 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
What is the role of androgens during ovulation?
Androgens rise midcycle, produced by theca cells of follicles that were recruited but not selected (underwent apoptosis).
55
What hormone suppresses new follicular growth in the luteal phase?
Progesterone
56
When do progesterone levels peak in the luteal phase?
Approximately 8 days after the LH surge.
57
What maintains luteal function if conception occurs?
hCG (human chorionic gonadotropin) until placental steroidogenesis is established.
58
What happens to the corpus luteum if conception does not occur?
It is maintained by LH but declines 9-11 days after ovulation. Menses occur about 14 days after ovulation.
59
What mechanisms are thought to cause regression of the corpus luteum?
Local prostaglandin production. Luteolytic action of its own estrogens
60
What regulates the ovarian cycle?
The ovarian cycle is regulated by steroid hormones (estrogen and progesterone) and autocrine/paracrine peptides acting on ovarian follicles.
61
What ensures a coordinated ovarian cycle?
The interplay between the hypothalamus, pituitary, and ovaries through the release of GnRH, FSH, LH, estrogen, and progesterone.
62
What marks the transition from primordial follicles to pre-antral follicles?
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
What is the significance of FSH during the early follicular phase?
FSH stimulates follicular development and granulosa cell proliferation, increasing estrogen secretion.
64
How does the selection of a dominant follicle occur?
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
What effect does estrogen have on the hypothalamus and pituitary during the follicular phase?
Early phase: Negative feedback reduces FSH secretion. Late phase: Positive feedback triggers the LH surge.
66
What structural changes occur in the dominant follicle?
The dominant follicle enlarges, its granulosa cells proliferate, and it begins producing large amounts of estrogen.
67
What enzymes are activated during ovulation?
Proteolytic enzymes are activated to break down the collagen in the follicular wall, facilitating oocyte release.
68
What triggers the oocyte to resume meiosis?
The LH surge signals the oocyte to resume meiosis, progressing to metaphase II before ovulation.
69
What role do prostaglandins play in ovulation?
Prostaglandins increase within the follicle to aid follicular rupture and oocyte release.
70
How long after the LH surge does ovulation occur?
Ovulation occurs approximately 24-36 hours after the estradiol peak and 10-12 hours after the LH peak.
71
What structural feature supports oocyte release?
The stigma (a weakened spot on the follicle wall) ruptures, allowing the oocyte to exit the follicle.
72
What happens to the granulosa and theca cells post-ovulation?
They luteinize (transform into luteal cells) and form the corpus luteum, which secretes progesterone and estrogen.
73
Why is progesterone important during the luteal phase?
Progesterone stabilizes the endometrium, preparing it for implantation if fertilization occurs.
74
What is the lifespan of the corpus luteum in a non-conception cycle?
The corpus luteum degenerates after 9-11 days, leading to a drop in progesterone and the onset of menstruation.
75
What maintains the corpus luteum in a conception cycle?
hCG from the developing embryo maintains the corpus luteum until the placenta takes over hormone production.
76
What causes the decline of the corpus luteum in a non-conception cycle?
Declining LH levels, local prostaglandin production, and possible luteolytic effects of estrogens contribute to its regression.
77
How does the luteal phase ensure synchrony with the uterine cycle?
The peak in progesterone secretion corresponds with the secretory phase of the endometrium, preparing it for potential implantation.
78
What is the average length of the menstrual cycle?
The average interval is 25-35 days.
79
How long does menstrual flow typically last?
Menstrual flow lasts 3-6 days.
80
What is the average blood loss during menstruation?
Average blood loss is 30-80 mL.
81
How is a "regular" menstrual cycle defined?
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
What is an alternate definition of cycle regularity?
Cycle-to-cycle variation of ≤7 days (≤9 days at age extremes).
83
What determines the length of the menstrual cycle?
The length of the follicular phase is the major determinant of cycle length.
84
What happens to the endometrium during the follicular phase?
Under the influence of estrogen, the endometrium grows from 0.5 mm to 3.5-5.0 mm in height, becoming proliferative.
85
At what ages are anovulatory cycles most common?
Anovulatory cycles occur most commonly under 20 years and over 40 years.
86
Why do anovulatory cycles occur at these ages?
These age extremes represent periods when the hypothalamo-pituitary-ovarian (HPO) axis may be immature (in younger women) or declining (in older women).
87
What happens to the endometrium after ovulation?
Combined estrogen and progesterone secretion results in the development of the compact secretory endometrium.
88
How does the endometrium prepare for potential implantation?
The secretory phase produces a mature, glandular endometrium conducive to embryo implantation.
89
What triggers menstruation if fertilization does not occur?
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
What happens to the endometrium during menstruation?
The compact and functional layers are shed, leaving the basal layer intact.
91
How does ovarian steroidogenesis influence the endometrium?
- Estrogens promote proliferation during the follicular phase. - Combined estrogen and progesterone stabilize and mature the endometrium in the luteal phase.
92
What is the maximum acceptable inter-menstrual interval for a "regular" cycle?
35 days.
93
What is the minimum inter-menstrual interval for a "regular" cycle?
21 days.
94
What is the significance of inter-cycle variation?
For regular cycles, the inter-cycle variation should not exceed 4 days in an individual.
95
What hormone drives the changes in the endometrium during the follicular phase?
Estrogens
96
How thick does the endometrium grow during the follicular phase?
It grows from approximately 0.5 mm to 3.5-5.0 mm in height.
97
What is the state of the endometrium during the follicular phase?
The endometrium is in a proliferative state.
98
What marks the transition from the follicular phase to the luteal phase?
Ovulation, triggered by the LH surge.
99
What hormones are responsible for the secretory changes in the endometrium after ovulation?
Combined effects of estrogen and progesterone.
100
What happens to the endometrium during the secretory phase?
The endometrium becomes compact, glandular, and prepared for potential embryo implantation.
101
What causes the shedding of the endometrium in the absence of fertilization?
Falling concentrations of estrogen and progesterone.
102
What role do liposomal enzymes play in menstruation?
Liposomal enzymes initiate a chain of events that lead to the breakdown and shedding of the functional layer of the endometrium.
103
Which layer of the endometrium remains intact after menstruation?
The basal layer.
104
How do anovulatory cycles differ from ovulatory cycles?
Anovulatory cycles lack ovulation, meaning there is no LH surge, corpus luteum formation, or progesterone production.
105
How does an anovulatory cycle affect the endometrium?
The endometrium remains under estrogen stimulation without the stabilizing effects of progesterone, which may lead to irregular or heavy bleeding.
106
What is the most common cause of anovulatory cycles at age extremes?
Immaturity or decline in the hypothalamo-pituitary-ovarian (HPO) axis.
107
What are the three phases of the uterine cycle?
1. Menstrual phase Proliferative phase Secretory phase
108
What occurs during the menstrual phase of the uterine cycle?
The functional layer of the endometrium is shed, resulting in menstrual bleeding.
109
What triggers the menstrual phase?
A drop in estrogen and progesterone levels due to regression of the corpus luteum.
110
How long does the menstrual phase typically last?
It lasts 3-6 days.
111
What part of the endometrium remains intact after menstruation?
The basal layer.
112
What drives the proliferative phase of the uterine cycle?
Rising estrogen levels from developing ovarian follicles.
113
What happens to the endometrium during the proliferative phase?
The endometrium regenerates and thickens, growing from about 0.5 mm to 3.5-5 mm.
114
What structural changes occur in the endometrium during the proliferative phase?
Endometrial glands elongate and spiral arteries begin to form.
115
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Gynaecology (32 decks)

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