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Gynecology > Physiology - Gonadotropic hormones, female hormones and the menstrual cycle > Flashcards

Physiology - Gonadotropic hormones, female hormones and the menstrual cycle Flashcards

1
Q

What are the four stages of gametogenesis?

A

1) Extra-embryonic origin of germ cells and their migration into the gonads.
2) Increase in the number of germ cells due to mitosis.
3) Decrease in chromosomal number by meiosis.
4) Structural and functional maturation of oocytes and spermatozoa.

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2
Q

At what time does the number of germ cells in women peak?

A

5 months after conception.

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3
Q

At what stage of meiosis is the primary oocytes arrested until meiotic resumption in puberty?

A

The diplotene stage in meiosis 1.

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4
Q

When does the spermatogonia start and finish meiosis?

A

From puberty. (Unlimited production of new spermatogonia in the testes.)

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5
Q

When does the oocytes finish meiosis 1 and 2?

A

Meiosis 1 is finished after puberty. (One primary oocytes gives rise to one secondary oocyte and one polar body.)
Meiosis 2 is finished after fusion and the secondary oocytes and sperm cells. (Halving the chromosome number, creating an ovum and a second polar body. After fusion of the spermatocyte and ovum nucleus it becomes a zygote.)

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6
Q

In what form is GnRH secreted? What receptor does it bind to?

A

Secreted as preproGnRH.

GnRH type 1 receptor which is a G protein coupled receptor.

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7
Q

True or false: Most gonadotrophes secretes both luteinising-hormone (LH) and folliclestimulating hormone (FSH).

A

True. Although not equal in amounts.

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8
Q

What is the pulse frequency and amplitude of GnRH neurons dependent upon?

A

Variable firing patterns appear to be intrinsic to GnRH
neurons, but may be altered by neurotransmittors and
neuromodulators.
It is dependent upon: Age, sex (male/female), time of day, and phase of menstrual cycle.

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9
Q

Is LH secretion mainly stimulated by high of low frequency GnRH?

A

High frequency.

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10
Q

Is FSH secretion mainly stimulated by high or low frequency of GnRH?

A

Low frequency.

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11
Q

Where are the human gonadotropins produced?

A

Two are produced in the anterior pituitary gland, FSH and LH.
One is produced in the placenta, hCG.

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12
Q

Why is pulsatile GnRH secretion absolutely required for long-term stimulation of gonadotropin synthesis and secretion?

A

Continuous GnRH receptor stimulation leads to marked
desensitization of gonadotropin synthesis and secretion, while intermittent GnRH stimulation increases (or maintain) GnRH receptors on gonadotropes.

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13
Q

How are gonadotropins built? What are the functions of each unit?

A

Gonadotropins consist of one alpha unit and one beta unit. The alpha unit is responsible for receptor binding, while the beta unit is involved in hormone specificity.

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14
Q

What hormones can bind to the LH receptor? What cells have this receptor?

A

Both LH and hCG can bind to the LH receptor.

Leydig, theca, granulosa and luteal cells have this receptor.

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15
Q

What hormones can bind to the FSH receptor? What cells have this receptor?

A

FSH can bind to the FSH receptor.

Granulosa and sertolli cells have this receptor.

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16
Q

What inhibits GnRH release at the hypothalamic level?

A

Medication/drugs.
Stress.
Sex hormones.
Prolactin.

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17
Q

What is the effect of high estrogen levels on the secretion/effect of GnRH at the hypothalamic and pituitary levels?

A

Hypothalamic level: Increased amplitude and frequency of GnRH pulses.
Pituitary level: Increased levels of GnRH receptors on gonadotropes and enhancement of post-receptor signaling.

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18
Q

Functional hypothalamic amenorrhea is a reversible condition of suppressed hypothalamic-pituitary function. What is this condition often accompanied by?

A

Reduced body weight, disordered eating (anorexia nervosa).
Excessive exercise (“female athletic triad”).
Psychological stress.

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19
Q

True or false: It is usually required cooperative efforts by two different tissues or cell types to generate estrogen from cholesterol.

A

True. It is rare

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20
Q

What are effects sulfatase and sulfotransferases?

A

Sulfatase and sulfotransferases have pivotal roles in inactivating and potentiating sex-steroids in various tissues. E.g.: In the placenta key role in placental estrogen synthesis by liberating sulfonated androgen precursors.

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21
Q

Where in the cell are the estrogen, progesterone and androgen receptors located?

A

Estrogen receptor is usually located in the nucleus.

Progesterone receptor and androgen receptor is located in the cytosol.

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22
Q

What are general factors effecting steroid hormone action?

A 
Hormone availability.
Expression of hormone receptors.
Binding of hormones to their receptors.
Receptor phosphorylation.
Interaction with DNA, co-factors and transcription factors.
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23
Q

The majority of steroid hormones are bound to plasma proteins. What proteins bind estrogen, testosterone and progesterone?

A

Sex hormone binding globulin (SHBG) binds estradiol and testosterone.
Corticosteroid-binding globulin (CBG) bind progesterone (and some testosterone).
Albumin binds estrogen, progesterone and testosterone.

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24
Q

How is the majority of circulating steroid hormones removed from the blood?

A

By the liver.

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25
Q

What is the name of the enzyme converting androgens (testosterone and androstendion) into estrogen and estradiol?

A

Aromatase.

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26
Q

In what tissue/organs is androgens converted into estrogens?

A

Ovaries.
Placenta.
Peripheral circulation / fatty tissue.
Adrenal glands.

27
Q

What are the three major estrogens in females and where are they produced? What is the most and least potent?

A

Estradiol (E2) - produced in the ovaries. Most potent.
Estriol (E3) - produced in the placenta.
Estrone (E1) - produced in fatty tissue. Least potent.

28
Q

What organs have estrogen receptors?

A

Most organs like skeleton, kidneys, liver, heart, vessel walls, brain, internal and external genitalia and breasts.

29
Q

What effects do estrogen have on development during puberty in females?

A

Growth of genitalia.
Growth and development of breasts.
Skeletal development and growth. (Inhibits bone resorption, closes epiphysial plates, and accelerates growth.)
Slightly anabolic effect (builds muscle, fat deposition).

30
Q

What are the biological effects of estrogens in the fallopian tubes?

A

Increased epithelial cells.
Increased blood flow of the oviducts.
Increases the production of oviduct specific glycoproteins.
Increased ciliogenesis.

31
Q

What are the biological effects of estrogens in the uterus?

A

Increased number of smooth muscle cells and increased contraction of the myometrium.
Proliferation of endometrium (directly and indirectly).
Preparing the endometrium for the luteal phase by inducing progesterone receptors.

32
Q

What are biological effects of estrogens on the cervix?

A

Stimulates production of a copious quantity of thin, watery, slightly alkaline mucus that is an ideal environment for sperm.

33
Q

What are biological effects of estrogens on the vagina?

A

Induces keratinization of the apical layers.

Stimulates proliferation of the vaginal epithelium and increases glycogen content.

34
Q

What are biological effects of estrogens on bone?

A

Closure epiphyseal plates of long bones in both sexes.

Anabolic effect and a calciotropic effect (intestinal Ca++
absorption and renal tubular Ca++ reabsorption).

Potent regulators of osteoblast and osteoclast function.
(Survival of osteoblasts and apoptosis of osteoclasts).

35
Q

What are biological effects of estrogens on cardiovascular system?

A

Estrogen promotes vasodilation through increased production of nitric oxide (NO), which relaxes vascular smooth muscle and inhibits platelet activation.

Estrogen promotes angiogenesis in target tissues.

36
Q

What is the general effect of estrogen on adipose tissue?

A

It decreases adipose tissue.

37
Q

What is the biological effect of progesterone on the uterus?

A

Prepare uterus for implantation of fertilized ovum.
Uterine glands to secrete a nutrient-rich product.
Adhesivety of the surface epithelium, generating the
“window of receptivity for implantation”.
Differentiation of the stromal cells into predecidual cells.
Progesteron oposes the effects of estrogens (down-regulates receptors, inactivates estradiol)
Reduces contraction of the myometrium.

38
Q

What are the effects of progesterone on the hypothalamus and pituitary gland?

A 
Negative feedback (GnRH, LH, FSH).
Body temperature increase (0.5 degrees C).
Respiratory frequency increase.
Appetite increase.
Weak aldosterone antagonist.
More sleep?
39
Q

What is usually termed as reproductive age in women?

A

15-45 years.

40
Q

What is the average age of menarche in Norway?

A

13 years.

41
Q

What is the functional unite of the ovary?

A

The follicle.

42
Q

What are the functions of the ovarian follicles?

A

Maintains and nurtures the oocyte.
Matures the oocyte and release it at the right time.
Prepares the vagina and fallopian tubes to assist fertilization.
Prepares the lining of the uterus.
Maintain hormonal support for the fetus until placenta can take over.

43
Q

For how long may meiotic arrest in meiosis 1 last for the primary oocyte?

A

Up to 50 years.

44
Q

How many follicles are there in the ovaries at birth? How many are there left by the age of reproductive maturity?

A

At birth: 1 million.

At age of reproductive maturity: 300 000.

45
Q

How many follicles will mature between menarche and menopause?

A

400-500.

46
Q

True or false: Whether resting primordial follicles enter the early growth phase is dependent entirely upon LH and FSH from the pituitary gland.

A

False. It is dependent upon paracrine factors, not the pituitary gonadotropins.

47
Q

What are the main differences between primordial and primary follicles?

A

In the primordial follicle there is only a single layer of flat granulosa cells surrounding the ooctye.

In the primary follicle the granulosa cells become cuboid and proliferate. The granulosa cells express FSH receptors. Zona pellucida begins to form.

48
Q

What is the average duration of a menstrual cycle?

A

28 days.

49
Q

What are the names of the phases in the ovarian cycle?

A

Follicular phase of luteal phase.

50
Q

What are the names of the phases in the uterine cycle?

A

Proliferative phase, secretory phase and menstrual phase.

51
Q

At what day in the menstrual cycle is ovulation?

A

Day 14.

52
Q

What phases of the uterine and ovarian cycle occur simultaneously? What phases start at day 0?

A

The ovarian follicular phase occur simultaneously as the menstrual phase and proliferative phase in the uterus. They start at day 0 and end with ovulation.

The ovarian luteal phase occurs simultaneously to the secretory phase i uterus. They start at ovulation and at day 0.

53
Q

How many ovarian follicles growth each month during the follicular phase?

A

15-20.

54
Q

Where is inhibin produced? What is inhibin’s effect on FSH and LH?

A

Iinhibin is produced the testes and ovaries.
Inhibin inhibits the secretion of FSH from the pituitary gland, and increases the effect FSH and LH have on production of sex hormones in the gonads.

55
Q

What is characteristic for the gonadotropines and sex hormones during the early follicular phase?

A

GnRH and FSH is secreted due to low levels of ovarian hormones (inhibin and estradiol).
Theca cells express LH receptors and produce weak androgens.
FSH receptors on the granulosa cells are acitivated. This increased aromatase, which in turn increased production of estradiol.

56
Q

Describe in short the relationshop between LH, FSH, theca cells and granulosa cells.

A

Theca cells are dependent upon LH to produce androgens. Granulosa cells repond to FSH mainly by aromatasing androgens into estrogens.

57
Q

Are the granulosa cells released with the oocytes at ovulation?

A

Only the cumulus granulosa cells are released with the oozytes at ovulation.

58
Q

What does it mean that estradiol has a role as a biological amplifier?

A

Estradiol, has an autokrine effect, and amplifies the effect of FSH, causing further production of estrogen even though FSH secretion decreases.

59
Q

What are the main feedback mechanisms during the follicular phase?

A

Negative feedback on GnRH because of moderate levels of estrogen.
As the estrogen levels increase it causes negative feedback on FSH.
Inhibin has a negative feedback on FSH.
High estrogen levels in the last part of the follicular phase has a positive feedback on GnRH - causing a LH surge and ovulation.
FSH decreases right before ovulation.

60
Q

How long after LH surge is the ovulation?

A

26-34 hours.

61
Q

What happens to the follicle during the luteal phase?

A

Vascularisation of the remaining mural granulosa cells.
Luteinisation of granulosa cells (luteal cells).
Uptake of cholesterol via LDL High production of estradiol and progesterone, inhibin A.
(Negative feedback on LH and FSH.)

62
Q

What happens in the uterus during the menstrual phase? What happens simultaneously in the ovaries?

A

Spasms in spiral arteries, necrosis of superficial part of the endometrium, bleeding, uterine contraction (prostacyclins).

In the ovaries new follicles are recruited to the follicular phase. Corpus luteum from the previous cycle regresses and the hormone levels drop.

63
Q

What happens in the uterus during the proliferative phase?

A

In the days following menstruation estradiol stimulates the remaining layer of cells in the endometrium to proliferate. Regeneration of endometrium, more stroma
cells, glands, blood vessels.

64
Q

What happens in the uterus during the secretory phase?

A

Progesterone stimulates the endometrium to secrete a glycogen rich nutrient medium to the fertilized egg.

Together with estradiol stimulates progesterone continued growth of endometrial vascular system.

Gynecology (7 decks)

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