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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
In the 3 gonadotrophs what is a similarity in their structure
All have alpha chains that are similiar
26
What are the differnces in the 3 gonadotrophs
Beta chains differ
27
How is the beta chain of LH and HCG
They differ very small compared to FSH
28
What receptor does LH bind to
LHCGR
29
What receptor does FSH bind to
FSHR
30
What receptor does HCG bind to
LHCGR
31
How does the hypothalamus and anterior pituitary gland communicate
Indirectly via vasculature
32
What is the role of gonads
To produce sex steroids and other regulatory factors e.g inhibition
33
What type of feedback does the hormones release by the gonads create
Regulatory feedback
34
What molecule are all steroids derived from
Cholesterol
35
What are the 3 families of sex steroids
Progesterone Androgens Oestrogen’s
36
What is the feedback in the males called
Negative feedback loop
37
What is the feedback in females like
More complicated, (will be explained in detail later)
38
What role does progesterone play a role in
In pregnancy
39
Where is progesterone produced
Ovaries | Placenta
40
What type of role does androgen have
Maleness (but also produced in the female)
41
Where are androgens produced
Gonads | Adrenal glands
42
What role does oestrogens play
Femaleness ( and some male)
43
Where are oestrogen produced
``` Ovaries Testis Liver Adrenal glands Adipose Placenta ```
44
Are sex steroid lipid soluble or lipid insoluble
Lipid soluble
45
If sex steroids are lipid soluble what does it mean in terms of the plasma membrane of a cell
It can pass into the cell
46
When sex steroids pass into the cell what receptors do they bind to
Nuclear receptors
47
What do the sex steroids act on the nuclear receptros via
Steroid response elements
48
If sex steroids are lipophilic what does this mean in terms of them being solution
They cannot be in solution
49
To allow sex steroid hormones to be in solution what are they bound to
Sex hormone binding globulin
50
What is sex hormone binding globulin
A carrier protein
51
Name another carrier protein that is present in the testis
Androgen binding protein
52
How are sex steroids produced
Progesterones form androgens | Androgens form the oestrogens
53
How many forms does progestagens have
3
54
Name the 3 forms of progestagens
Progesterone 17alpha-hydroxyprogesterone (17a-OHP) 20alpha-hydroxyprogesterone (20a-OHP)
55
What happens to potency of the progestagens as you go from progesterone to 20a-OHP
Decreases
56
What are the receptors of the progestagens
PR-A | PR-B
57
How many forms of androgen are there
4
58
Name the 4 forms of androgen
5alpha-dihydrotestosterone (DHT) Testesterone Androstenedione (A4) Dehydropiandrosterone (DHEA)
59
What receptors do androgens binds to
AR
60
What happen to the potency of androgens as you go from DHT to DHEA
Decrease
61
How many forms of oestrogen are there
3
62
Name the forms of oestrogen
Oestradiol 17beta (E2) Oestriol (E3) Oestrone (E1)
63
What are the receptors of oestrogens
ER-alpha | ER-beta
64
What happens to the potency of oestrogen as you go from E2 to E1
Decreases
65
How does the predominant form of oestrogen vary within the female lifecycle
Puberty to menopause: oestradial (E2) Pregnancy: oestriol (E3) Post menopause: oestrone (E1)
66
What is potency
How well it binds to its receptors
67
What are the 2 ways that we can regulate steroid action
1) alter amount of steroid produced | 2) alter amount or structure of receptors
68
What is central hypogonadism
Low FSH/LH due to a problem in the hypothalamus or pituitary i.e central because it cannot produce it
69
What is primary hypogonadism
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
what role does prolactin play a role in
Breastfeeding
71
When does prolactin increase
During pregnancy
72
What doe high levels of prolactin do to the HPG axis
Supress it
73
If the HPG axis is suppressed what happens to LH/FSH
Decreases
74
What is lactational ammenrrhoea
Absence of periods due to breastfeeding
75
What is abnormal increases in prolactin called
Hyperprolactinemia
76
What can hyperprolactinemia cause
Galactorrhea
77
What is galatactorrhea
Production of breast milk when you are not pregnant
78
Is the gametogenesis in males continous or cyclic
Continous
79
Is gametogenesis in females continous or cyclic
Cyclic - one oocyte released per month
80
What are the 3 phases of the menstrual cycle in females
Follicular Ovulation Luteal/secretory
81
What is the normal duration of the menstrual cycle
26-32 days
82
How long does the luteal phase last
14 days
83
Which phase of the menstrual cycle varies that determines the length of the menstrual cycle
Follicular phase
84
What is day 1
First day of period
85
What is oligomennorhea
Less than 9 cycles in the last 12 months
86
What is ammenorhea
No bleed in the last 6 months
87
What are 2 types of ammenorhhea
Primary | Secondary
88
What is primary ammenorhhea
Never had periods
89
What is secondary amennorhea
Had periods but stopped for some reason
90
What is mennorhagia
Heavy period
91
What is dysmenorrhea
Painful periods
92
Around what age does a female experience menopause
50
93
Why does a lady get menopoause
Ovarian reserve is depleted
94
What happens to the LH/FSH levels
High
95
Why is there high FSH/LH in menopause
Due to loss of negative feedback by sex steroids
96
What are hormonal contraception
Progestagens | Oestrogen
97
What does progesterone and oestrogens do
Supress ovulation Thickens cervical mucus Thins endometrium
98
What does fertility treatment involve
Down regulate the HPG axis with GNRH agonist/antagonist
99
How do we treat prostate cancer
GNRH antagonist to suppress T production

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