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Endocrine- Sex Hormones > Hypothalamic-Pituitary Axis and The Menstrual Cycle > Flashcards

Hypothalamic-Pituitary Axis and The Menstrual Cycle Flashcards

1
Q

What 2 hormones are secreted from the anterior pituitary gland in this axis?

A

LH and FSH

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2
Q

How are LH and FSH secreted? In response to what?

A

In pulses, in response to GnRH from the hypothalamus

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3
Q

What 2 hormones exert negative feedback on LH secretion and have multiple peripheral effects?

A

Testosterone and oestrogen

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4
Q

What exerts negative feedback on FSH secretion?

A

Inhibin

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5
Q

What is the function of LH in males? Where does it exert its action?

A

Production of testosterone from the Leydig cells of the testes

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6
Q

What type of receptor does testosterone act on?

A

Nuclear androgen receptors

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7
Q

What are the roles of testosterone once it has bound to its receptor?

A

Male secondary sex characteristics, anabolism, maintenance of libido, aids spermatogenesis

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8
Q

Testosterone circulates, mainly bound to what?

A

Sex-hormone binding globulin

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9
Q

Testosterone feeds back to inhibit secretion of what?

A

GnRH and LH

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10
Q

Where does FSH act in males?

A

Sertoli cells (spermatogenic) in the seminiferous tubules

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11
Q

What is the action of FSH at the Sertoli cells?

A

To produce mature sperm and produce inhibins A and B

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12
Q

What is the function of inhibin?

A

Feeds back to the anterior pituitary to decrease FSH production

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13
Q

What peptide counteracts inhibin?

A

Activin

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14
Q

From where exactly in the hypothalamus is GnRH released?

A

Arcuate nucleus

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15
Q

Describe the production of GnRH from the hypothalamus in an adult female?

A

A menstrual cycle of 28 days upon the activity of GnRH. Pulses are released at about 2 hour intervals.

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16
Q

Where does LH act in a female?

A

Theca cells

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17
Q

Where does FSH act in a female?

A

Granulosa cells

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18
Q

What is the function of LH in a female?

A

Stimulates ovarian androgen production (at the theca cells)

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19
Q

What has to occur for ovarian androgen production to occur?

A

ATP - cAMP

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20
Q

What are the 3 functions of FSH in a female?

A

Stimulate follicular development and activity of aromatase. Also stimulates release of inhibin from ovarian stromal cells.

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21
Q

What is aromatase?

A

An enzyme required to convert androgens to oestrogens

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22
Q

What must occur for aromatase to be produced?

A

ATP - cAMP

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23
Q

What hormone and enzyme mix to produce oestrogen?

A

Aromatase and androgen

24
Q

What chemical is the basis needed to produce oestrogen?

A

Cholesterol

25
Q

What is cholesterol converted to in the cycle to produce oestrogen?

A

Pregnenolone and then progesterone

26
Q

What exhibits a) positive feedback and b) negative feedback, on the change from pregnenolone to progesterone?

A

a) Inhibin (+), b) Activin (-)

27
Q

What is progesterone converted into which can finally be converted to oestrogen?

A

Androstenedione

28
Q

What exerts positive feedback on the conversion of androstenedione to oestrogen?

A

Activin

29
Q

When in the menstrual cycle does ovulation usually occur?

A

Day 14

30
Q

The follicular stage of the menstrual cycle begins when oestrogen levels are?

A

Low

31
Q

What stimulates the follicle to develop in the follicular stage of the menstrual cycle?

A

FSH

32
Q

What happens to the granulosa cells around the egg in the follicular stage of the menstrual cycle?

A

They enlarge, releasing oestrogen

33
Q

What does the increased oestrogen by the end of the follicular stage of the menstrual cycle do?

A

Causes thickening of the uterine lining

34
Q

What hormone level peaks at the beginning of the follicular stage of the menstrual cycle?

A

FSH

35
Q

What happens to oestrogen levels in the follicular stage of the menstrual cycle?

A

They start low and are raised at the end

36
Q

What is the relative concentration of progesterone throughout the follicular stage of the menstrual cycle?

A

Low

37
Q

When does ovulation occur?

A

At the peak of follicular growth, in response to an LH surge

38
Q

What happens after the LH peak in the ovulation stage of the menstrual cycle?

A

The oocyte is released into the ampulla of the fallopian tube

39
Q

What hormone has a large peak at the beginning of ovulation?

A

LH

40
Q

What hormone has a small peak at the beginning of ovulation?

A

FSH

41
Q

In the luteal phase of the menstrual cycle, why are the remaining granulosa cells around the egg yellow?

A

They absorb a lot of keratin

42
Q

What are the remaining granulosa cells known as in the luteal phase?

A

Corpus luteum

43
Q

What hormone does the corpus luteum secrete?

A

Progesterone

44
Q

When is there a peak of oestrogen in the luteal phase?

A

First 1/3rd of the phase

45
Q

What is the major hormone of the luteal phase?

A

Progesterone

46
Q

What hormones are responsible for endometrial proliferation in preparation for implantation?

A

Oestrogen initially and then progesterone

47
Q

If implantation does not occur, what happens to the corpus luteum?

A

It regresses, so progesterone and inhibin levels fall so that the endometrium is shed

48
Q

What hormones are increased again if no pregnancy occurs at the end of a menstrual cycle?

A

GnRH and FSH

49
Q

What hormone will be produced at the end of the menstrual cycle if a pregnancy has occurred?

A

HCG

50
Q

How is the ovary attached to the pelvic side wall?

A

Infundibulopelvic ligament

51
Q

What are the two parts of an ovary? Which contains the follicles?

A

Outer cortex and inner medulla, the cortex contains the follicles

52
Q

What components make up the uterus?

A

Body of the uterus and cervix

53
Q

Oestrogen acts synergistically with what other hormone?

A

FSH

54
Q

Where can oestrogen be synthesised?

A

Ovaries, but also adrenal glands, fat and bone

55
Q

What are both inhibin and activin and where are they found?

A

Peptides in follicular fluid

Endocrine- Sex Hormones (5 decks)

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