4/7 Basic Rev of Principles of Repro + Menst Cycle VIDEO

Question 1

The maximum number of oocytes is present when? drops when?

Answer 1

The maximum endowment of oocytes is present at birth and drops with time (at 40-50 y)

Note dropoff in #oocytes from 20 wks gestation to birth!

Question 2

Spermatogenesis begins when?

Answer 2

Spermatogenesis begins at puberty and continues throughout the lifetime.

Question 3

If you give an adult woman a constant infusion of GnRH, what would you see in terms of changes to her FSH levels?

Answer 3

Her FSH would rise immediately, but ultimately would fall and be suppressed – due to downregulation of the number of GnRH receptors.

Question 4

what is the driver of the H-P-A axis? what kind of secretion is required for normal repro function?

Answer 4

The arcuate nucleus and its production of GnRH is the driver of the hypothalamic-pituitary-gonadal axis.

Pulsatile secretion of GnRH is required for normal reproductive function.

Question 5

At puberty, what part of the HPA axis matures/awakens for proper functioning of reproduction?

Answer 5

“awakening” of the arcuate nucleus (within the hypothalamus)

Question 6

GnRH: what is it also called? what hormones does it stimulate?

Answer 6

GnRH aka LHRH

Stimulates both LH and FSH from the anterior pituitary

stimulates LH >>> FSH

Question 7

What does FSH stimulate in the female? male?

Answer 7

Female: FSH stimulates Granulosa Cells in the ovary –> follicular development

Male: FSH stimulates seminiferous tubules

Bottom line: FSH –> germ cell production in both F and M.

Question 8

What does LH stimulate in the female? male?

Answer 8

Female: LH stimulates the theca cells in the ovary to convert cholesterol to androgens

Male: LH stimulates the Leydig cells to produce testosterone

Question 9

How do we use GnRH agonists for therapeutic treatment?

Answer 9

Can give a GnRH agonist in order to shut off the HPO circuit.

ex: endometriosis, if we want to decrease the amount of systemic estrogen. Works because the pituitary will be desensitized to GnRH (downreg of GnRH receptors)

Question 10

If GnRH is suppressed, what happens to levels of LH and FSH?

Answer 10

Pituitary will release NO LH

some FSH (some FSH is secreted regardless of GnRH levels)

Question 11

A 4 yo boy has an androgen producing tumor. What will happen to his LH levels compared with his pre-tumor levels?

Answer 11

LH will be lower than pre-tumor levels

(Too much testosterone will suppress GnRH production in the hypothalamus due to negative feedback)

Question 12

The HPG axis is under the primary control of positive or negative feedback?

Answer 12

Negative

Question 13

For the LH surge and subsequent ovulation, is positive or negative feedback required?

Answer 13

Postive feedback.

Question 14

If a woman loses all of her follicles (due to radiation or something), will she still have any oocytes? any estrogen production?

Answer 14

She will have neither oocytes or estrogen production

These are linked in one compartment (the follicle) in the female system. Loss of follicle = loss of ability to make estrogen and loss of ability to reproduce

Question 15

What does the theca cell do? What stimulates it?

Answer 15

In the ovary, Theca cell is stimulated by LH.

Converts cholesterol into androgens

Question 16

What does the Granulosa cell do? What stimulates it?

Answer 16

In ovary, Granulosa cell aromatizes androgen to estrogen and then to estradiol.

Stimulated by FSH

(remember which is which because F and G are next to each other in the alphabet

FSH –> Granulosa cell

LH –> Theca cell)

Question 17

where do the proceses of spermatogenesis and androgen production take place?

Answer 17

in the testes

Question 18

Generally are spermatogenesis and androgen production in the male linked?

What could affect both processes?

Answer 18

Generally these two processes are separate - men can have normal androgen levels alongside abnormal spermatogenesis

Could both be affected with a tumor in the hypothalamus or pituitary, or a genetic cause like Klinefelter’s

Question 19

In the male, what does FSH do?

Answer 19

In the testis, FSH stimulation of seminiferous tubules (with initiation of spermatogenesis) causes the initial increase of testicular size at puberty (first sign of puberty in males).

Question 20

In the male, what does LH do?

Answer 20

In testis: LH Stimulation of Leydig Cells causes 10 fold increase in testicular testosterone production (later in puberty).

Leydig cells constitute < 10% of adult testicular mass

Question 21

Describe the axis which causes spermatogenesis in males.

(Hypothal –> GnRH –> Pituitary ….etc)

Answer 21

(axis on the left)

Question 22

Describe the axis which causes androgen production in males.

(Hypothal –> GnRH –> Pituitary etc)

Answer 22

(axis on the right)

Question 23

How long is a normal (ovulatory) menstrual cycle?

How long is the follicular phase?
how long is the luteal phase?

Answer 23

normal/ovulatory cycle = 21-35 d (mean is 29d)

Follicular: variable length

Luteal: ALWAYS 14d +/- 2d

Question 24

If a woman makes too much estrogen (or makes normal estrogen but no progesteron), what is she at risk for?

Answer 24

If woman makes nothing but estrogen, precursor to endometrial cancer.

Overgrowth of estrogen –> overgrowth of endometrium –> endometrial cancer.

Progesterone is needed to prevent this overgrowth.

Question 25

Two parts of the menstrual phase? what are they alternatively called?

what event divides them?

Answer 25

Follicular (aka Proliferative)

Luteal (aka Secretory)

Divided by Ovulation

Question 26

What marks the start of the follicular phase? the end?

Answer 26

Start = onset of menses

End = Ovulation

Question 27

What marks the start of the luteal phase? the end?

Answer 27

Start = ovulation

End = onset of menses

Question 28

During the Follicular phase, what generally is going on?

Answer 28

A batch (cohort) of follicles reach the point of maturation where they are Gn-sensitive.

One is selected as dominant - that one will mature and ovulate.

The others undergo atresia/die off.

Question 29

How is one follicle determined to be the dominant one in its cohort?

Answer 29

There’s competition for FSH that allows a dominant follicle to emerge based on its having more FSH receptors than the others.

The smaller follicles die off due to lack of FSH

Question 30

After ovulation, what happens to the dominant follicle?

Answer 30

It becomes the Corpus Luteum, lasts for the duration of the cycle.

Secretes progesterone.

Question 31

What generally is going on during the Luteal phase?

Answer 31

Corpus Luteum (former dominant follicle) is secreting progesterone.

If the Corpus Luteum does not get hCG by day 9 of Luteal phase, it stops producing estrogen and progesterone and dies.

Question 32

In the context of reproduction, what do these numbers represent?

• 5 days
• 250 (units?)
• 12 hrs
• 40 hrs
• 9 days
• 14 days

Answer 32

• 5 days = time for a dominant follicle to emerge from its cohort
• 250 (units?) = Peak estrogen level: causes LH surge
• 12 hrs = Time between peak estrogen level and LH surge
• 40 hrs = Time from LH surge to follicle rupture and ovulation
• 9 days = if Corpus Luteum is not exposed to hCG within 9 days after ovulation, it will stop producing est and progest and die.
• 14 days = Max time the Corpus Luteum can survive without exposure to hCG. Also length of Luteal phase

Question 33

During the follicular phase, what is the effect of estrogen on the endometrium?

Answer 33

Estrogen stimulates the production of estrogen and progesterone receptors on the endometrium.

The effect of estrogen on the estr receptors –> proliferation of the endometrium (“Like watering a field of grass”)

Question 34

What is the dominant hormone during the Luteal phase? what does it do?

Answer 34

Progesterone dominates during Luteal phase.

It limits the number of receptors on the endometrium and thereby halts endometrial growth.

Also causes endometrial cells to become secretory

(creating secretions needed for implantation)

Question 35

In the absence of a pregnancy, what happens with estrogen and progesterone levels?

what is the result?

Answer 35

No pregnancy –> estrogen and progesterone levels decline

Causes production of Prostaglandins –> arteriolar spasm –> shedding of endometrium –> menstrual period.

Bottom line: withdrawal of progesterone at end of luteal phase –> menses)

Question 36

What are signs that a cycle is ovulatory?

Answer 36

• cycles lasting 21-35 days are almost always ovulatory
• Breast tenderness, bloating indicates presence of progesterone
• Menstrual cramps - produced by ovulatory endometrium
• Increased basal body temp - during Luteal phase, can rise as much as one degree with ovulation.

(Also rises in first trimester of preg.!!)

Question 37

Describe theh general behavior of progesterone over the menstrual cycle.

Answer 37

Progesterone: secreted from the Corpus Luteum.

Low during Follicular Phase.

Slow rise and fall during Luteal phase.

Question 38

General behavior of Estrogen during menstrual cycle?

Answer 38

Estrogen is secreted by the dominant follicle.

Peaks at the end of the Follicular phase (at a level of approx 250). Causes LH surge 12 h later.

With demise of Corpus Luteum, estrogen has its nadir (lowest point), causing FSH to rise mid-Luteal phase.

Rising FSH stimulates a new corhort of follicles, which will secrete estrogen

Question 39

General behavior of LH during the menstrual cycle?

Answer 39

LH surges 12 h after the Estrogen peak, causing ovulation and the onset of the Luteal phase

Question 40

General behavior of FSH during the menstrual cycle?

Answer 40

Peaks at same time as LH (but to lesser degree)

with low estrogen at the start of the Follicular phase, FSH levels rise and stimulate estrogen release from the cohort of follicles.