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RED > L01: HPG Axis > Flashcards

L01: HPG Axis Flashcards

1
Q

What is the HPG axis

A

Hypothalamus pituitary gonads axis

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2
Q

What hormone does the hypothalamus release in females and males

A

GNRH

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3
Q

Where does GNRH act in the head

A

Anterior pituitary gland

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4
Q

What does the anterior pituitary gland release to the gonads in female and male

A

LH

FSH

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5
Q

What are the female gonads

A

Ovary

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6
Q

What are the male gonads

A

Testis

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7
Q

What hormone does the testis produce

A

Inhibin

Testosterone

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8
Q

What hormone does the ovary produce

A

Oestrogen

Progesterone

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9
Q

What happens to the gonads at puberty

A

They are activated

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10
Q

How is GNRH triggered

A

A pulsatile secretion

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11
Q

Why is it important to have pulsatile release of GNRH and not a continuous release

A

A continuous release of GNRH leads to down regulation of GNRH receptors

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12
Q

Where are GNRH receptors found

A

In the surface of gonadotroph cells in the anterior pituitary gland

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13
Q

What would happen to the levels of FSH/LH if there was a continuous flow of GNRH

A

No stimulation of FSH and LH

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14
Q

What other hormones does the anterior pituitary gland release

A 
Acth 
Tsh
Gh 
LH 
FSH
Prolactin
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15
Q

What hormone does the posterior pituitary gland release

A

ADH

Oxytocin

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16
Q

What does FSH stand for

A

Follicle stimulating hormone

Luteinising hormone

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17
Q

What is the third important gonadotropin but not produced in the pituitary gland called

A

HCG

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18
Q

What type of substances are gonadtrohps

A

Glycoproteins

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19
Q

What type of receptors does glycoproteins bind to

A

GCPRs

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20
Q

What cell is LH and FSH secreted by

A

Gonadotrophs

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21
Q

What cell is HCG secreted by

A

Trophoblast cells in the embryo

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22
Q

What type of cells does LH act on

A

Leydig
Theca
Granulosa cells

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23
Q

What type of cells does FSH act on

A

Sertoli

Granulosa cells

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24
Q

What type of cells does HCG act on

A

Luteal cells in the corpus luteum

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25
Q

In the 3 gonadotrophs what is a similarity in their structure

A

All have alpha chains that are similiar

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26
Q

What are the differnces in the 3 gonadotrophs

A

Beta chains differ

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27
Q

How is the beta chain of LH and HCG

A

They differ very small compared to FSH

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28
Q

What receptor does LH bind to

A

LHCGR

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29
Q

What receptor does FSH bind to

A

FSHR

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30
Q

What receptor does HCG bind to

A

LHCGR

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31
Q

How does the hypothalamus and anterior pituitary gland communicate

A

Indirectly via vasculature

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32
Q

What is the role of gonads

A

To produce sex steroids and other regulatory factors e.g inhibition

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33
Q

What type of feedback does the hormones release by the gonads create

A

Regulatory feedback

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34
Q

What molecule are all steroids derived from

A

Cholesterol

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35
Q

What are the 3 families of sex steroids

A

Progesterone
Androgens
Oestrogen’s

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36
Q

What is the feedback in the males called

A

Negative feedback loop

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37
Q

What is the feedback in females like

A

More complicated, (will be explained in detail later)

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38
Q

What role does progesterone play a role in

A

In pregnancy

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39
Q

Where is progesterone produced

A

Ovaries

Placenta

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40
Q

What type of role does androgen have

A

Maleness (but also produced in the female)

41
Q

Where are androgens produced

A

Gonads

Adrenal glands

42
Q

What role does oestrogens play

A

Femaleness ( and some male)

43
Q

Where are oestrogen produced

A 
Ovaries 
Testis 
Liver 
Adrenal glands
Adipose 
Placenta
44
Q

Are sex steroid lipid soluble or lipid insoluble

A

Lipid soluble

45
Q

If sex steroids are lipid soluble what does it mean in terms of the plasma membrane of a cell

A

It can pass into the cell

46
Q

When sex steroids pass into the cell what receptors do they bind to

A

Nuclear receptors

47
Q

What do the sex steroids act on the nuclear receptros via

A

Steroid response elements

48
Q

If sex steroids are lipophilic what does this mean in terms of them being solution

A

They cannot be in solution

49
Q

To allow sex steroid hormones to be in solution what are they bound to

A

Sex hormone binding globulin

50
Q

What is sex hormone binding globulin

A

A carrier protein

51
Q

Name another carrier protein that is present in the testis

A

Androgen binding protein

52
Q

How are sex steroids produced

A

Progesterones form androgens

Androgens form the oestrogens

53
Q

How many forms does progestagens have

A

3

54
Q

Name the 3 forms of progestagens

A

Progesterone
17alpha-hydroxyprogesterone (17a-OHP)
20alpha-hydroxyprogesterone (20a-OHP)

55
Q

What happens to potency of the progestagens as you go from progesterone to 20a-OHP

A

Decreases

56
Q

What are the receptors of the progestagens

A

PR-A

PR-B

57
Q

How many forms of androgen are there

A

4

58
Q

Name the 4 forms of androgen

A

5alpha-dihydrotestosterone (DHT)
Testesterone
Androstenedione (A4)
Dehydropiandrosterone (DHEA)

59
Q

What receptors do androgens binds to

A

AR

60
Q

What happen to the potency of androgens as you go from DHT to DHEA

A

Decrease

61
Q

How many forms of oestrogen are there

A

3

62
Q

Name the forms of oestrogen

A

Oestradiol 17beta (E2)
Oestriol (E3)
Oestrone (E1)

63
Q

What are the receptors of oestrogens

A

ER-alpha

ER-beta

64
Q

What happens to the potency of oestrogen as you go from E2 to E1

A

Decreases

65
Q

How does the predominant form of oestrogen vary within the female lifecycle

A

Puberty to menopause: oestradial (E2)
Pregnancy: oestriol (E3)
Post menopause: oestrone (E1)

66
Q

What is potency

A

How well it binds to its receptors

67
Q

What are the 2 ways that we can regulate steroid action

A

1) alter amount of steroid produced

2) alter amount or structure of receptors

68
Q

What is central hypogonadism

A

Low FSH/LH due to a problem in the hypothalamus or pituitary i.e central because it cannot produce it

69
Q

What is primary hypogonadism

A

High FSH and LH because the gonads are not responding to FSH/LH and so are not producing the sex steroids to inhibit it causing lack of feedback.

70
Q

what role does prolactin play a role in

A

Breastfeeding

71
Q

When does prolactin increase

A

During pregnancy

72
Q

What doe high levels of prolactin do to the HPG axis

A

Supress it

73
Q

If the HPG axis is suppressed what happens to LH/FSH

A

Decreases

74
Q

What is lactational ammenrrhoea

A

Absence of periods due to breastfeeding

75
Q

What is abnormal increases in prolactin called

A

Hyperprolactinemia

76
Q

What can hyperprolactinemia cause

A

Galactorrhea

77
Q

What is galatactorrhea

A

Production of breast milk when you are not pregnant

78
Q

Is the gametogenesis in males continous or cyclic

A

Continous

79
Q

Is gametogenesis in females continous or cyclic

A

Cyclic - one oocyte released per month

80
Q

What are the 3 phases of the menstrual cycle in females

A

Follicular
Ovulation
Luteal/secretory

81
Q

What is the normal duration of the menstrual cycle

A

26-32 days

82
Q

How long does the luteal phase last

A

14 days

83
Q

Which phase of the menstrual cycle varies that determines the length of the menstrual cycle

A

Follicular phase

84
Q

What is day 1

A

First day of period

85
Q

What is oligomennorhea

A

Less than 9 cycles in the last 12 months

86
Q

What is ammenorhea

A

No bleed in the last 6 months

87
Q

What are 2 types of ammenorhhea

A

Primary

Secondary

88
Q

What is primary ammenorhhea

A

Never had periods

89
Q

What is secondary amennorhea

A

Had periods but stopped for some reason

90
Q

What is mennorhagia

A

Heavy period

91
Q

What is dysmenorrhea

A

Painful periods

92
Q

Around what age does a female experience menopause

A

50

93
Q

Why does a lady get menopoause

A

Ovarian reserve is depleted

94
Q

What happens to the LH/FSH levels

A

High

95
Q

Why is there high FSH/LH in menopause

A

Due to loss of negative feedback by sex steroids

96
Q

What are hormonal contraception

A

Progestagens

Oestrogen

97
Q

What does progesterone and oestrogens do

A

Supress ovulation
Thickens cervical mucus
Thins endometrium

98
Q

What does fertility treatment involve

A

Down regulate the HPG axis with GNRH agonist/antagonist

99
Q

How do we treat prostate cancer

A

GNRH antagonist to suppress T production

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