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Endocrinology > Lec2 - Hypothalamic Pituitary Axis > Flashcards

Lec2 - Hypothalamic Pituitary Axis Flashcards

- Overview of hypothalamic-pituitary axis - Assessment of anterior pituitary function - MRI and visual field assessment in patients with HPA disease

1
Q

What is the area of the brain directly above the pituitary gland?

A

Hypothalamus

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2
Q

The pituitary gland is connected to the brain via the

A

Infundibulum

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3
Q

Trauma to the head, causing the infundibulum to get snapped can result in?

A

Endocrine problems, with effects on the ovaries and testes etc.

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4
Q

What happens if the pituitary gland becomes enlarged?

A

It can press on the optic chiasm, causing bilateral hemianopsia

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5
Q

The infundibulum contains

A

The hypothalamico-hypophyseal tract &

the hypothalamico-hypophyseal portal vessels

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6
Q

Name the two portions of the pituitary gland

A

The anterior pituitary gland &

posterior pituitary gland

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7
Q

How do the anterior and posterior pituitary glands function in relation to one another?

A

Independently

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8
Q

The posterior pituitary gland is what type of growth from the brain

A

A “down growth”

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9
Q

The posterior pituitary is also known as:

A

Neurohypophysis

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10
Q

Name the hormones stored and secreted from the posterior pituitary gland

A

Anti-diuretic hormone (ADH)/ Vasopressin

Oxytocin

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11
Q

What type of hormones are ADH and oxytocin?

A

Peptide hormones

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12
Q

How many amino acids in ADH and oxytocin?

A

Nine amino acids

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13
Q

How many of the amino acids are identical in ADH and oxytocin?

A

7

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14
Q

What does is the significance of the fact that there are 7 identical amino acids in ADH and oxytocin?

A

That at high concentrations of each, there can sometimes be cross over of activity e.g. at high concentrations of ADH it has some of the effects of oxytocin

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15
Q

Where are the hormones ADH and oxytocin synthesised?

A

In neurons of the hypothalamus:
Supraoptic nuclei
Paraventricular nucleus of the hypothalamus

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16
Q

In what form are ADH and oxytocin synthesised?

A

They are synthesised as inactive precursor hormones

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17
Q

Where are ADH and oxytocin converted into active hormones?

A

In the posterior pituitary gland

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18
Q

The inactive hormones are transported from the supraoptic nuclei and paraventricular nucleus to the pituitary gland via the:

A

Hypothalamico-neurohypophyseal tract

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19
Q

What is secretion of ADH influenced by?

A

Plasma osmolarity

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20
Q

ADH causes stimulation of what receptors?

A

V2 receptors

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21
Q

Stimulation of v2 receptors results in:

A

translocation of aquaporins to the membrane of the kidney tubule, allowing water reabsorption

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22
Q

ADH reabsorbs water in the kidney tubule so

A

there is less urine output

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23
Q

If there is dehydration, what happens to ADH?

A

ADH is secreted

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24
Q

Dehydration can also occur during haemorrhage which leads to a:

A

reduction in blood pressure

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25
Q

At high concentrations ADH causes:

A

an increase in blood pressure

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26
Q

Disorders of ADH secretion lead to:

A

disorders of fluid balance

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27
Q

A reduction in ADH secretion leads to:

A

an increase in urine volume

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28
Q

What is DIABETES INSIPIDUS?

A

A lack of ADH secretion

resulting in high volume of diluted urine

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29
Q

How do you treat DI?

A

By giving ADH

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30
Q

Increased ADH leads to:

A

Syndrome of Inappropriate ADH (SIA)

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31
Q

Syndrome of Inappropriate ADH causes:

A

very dilute blood and produce very little urine

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32
Q

How do you treat SIA?

A

Removal of the tumour and restrict fluid intake

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33
Q

Oxytocin acts via which second messenger?

A

IP3

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34
Q

Oxytocin causes

A

contraction of the smooth muscle of the uterus and breast

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35
Q

Oxytocin is most important during:

A

parturition and lactation

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36
Q

Secretion of oxytocin is stimulated by:

A

stimulation of the genitals and nipples

37
Q

Stimulation of V1 receptors cause:

A

Vasoconstriction but this does not happen at physiological concentrations of ADH

38
Q

Oxytocin synthesis increases during

A

pregnancy

39
Q

An increase in oxytocin synthesis during pregnancy also results in a parallel increase in:

A

oxytocinase activity

40
Q

During parturition, oxytocin causes contraction of smooth muscle of the uterus to aid:

A

expulsion of the foetus

41
Q

What is oxytocin responsible for after parturition?

A

For milk ‘let down’ / expulsion

42
Q

What is the stimulus for milk let down?

A

Suckling, but there is a delay between the start of suckling and milk let down

43
Q

Many women start secreting oxytocin when they hear what?

A

When they hear the baby crying

44
Q

Is oxytocin necessary for the initiation of normal labour?

A

No

45
Q

Why is administration of oxytocin to induce labour not part of current NICE guidelines?

A

Because oxytocin causes the uterus to contract but if the cervix hasn’t dilated, then the baby has nowhere to go and this can cause damage to the baby

46
Q

The anterior pituitary gland is what type of growth from the palate?

A

An upgrowth

47
Q

Name the hormones stored and secreted from the anterior pituitary gland:

A 
Adrenocorticotrophic hormone (ACTH)
Growth hormone (GH)
Thyroid stimulating hormone (TSH)
Follicle stimulating hormone (FSH)
Luteinising hormone (LH)
Prolactin (PRL)
48
Q

Prolactin is involved in

A

milk synthesis

49
Q

Oxytocin is involved in

A

milk expression

50
Q

Thyroid stimulating hormone is synthesised by:

A

thyrotrophe cells

51
Q

Adrenocorticotrophic hormone is synthesised by:

A

corticotrophe cells

52
Q

Follicle stimulating hormone (FSH) is synthesised by:

A

gonadotrophe cells

53
Q

Tumours of the pituitary gland can cause:

A

excess secretion of one or all of the hormones secreted by the pituitary gland

54
Q 
The hypothalamus secretes:
Thyrotrophin Releasing Hormone (TRH)
Corticotrophin Releasing Hormone (CRH)
Gonadotrophin Releasing hormone (GnRH)
Growth Hormone Releasing Hormone (GHRH)
A 
to stimulate secretion of:
Thyroid stimulating hormone (TSH)
Adrenocorticotrophin hormone (ACTH)
Follicle Stimulating Hormone (FSH)
Growth Hormone (GH)
55
Q

The releasing hormones are released by the hypothalamus into the:

A

hypothalamico-adenohypophyseal portal vessels which carry them into the anterior pituitary gland

56
Q

Do the releasing hormones enter the systemic circulation?

A

No

57
Q

The signs are

A

what the doctor can see

58
Q

The symptoms are

A

what the patient reports

59
Q

What biochemical tests should be done?

A 
TSH & FT4
Cortisol
LH and FSH
PRL
Testosterone/ ask about periods
60
Q

Why do we measure FSH?

A

To see whether the problem is in the pituitary or in the ovary

61
Q

How do we learn about the female sex hormones in a patient?

A

By asking a woman about her periods

62
Q

How can we tell about testosterone levels in a man?

A

By looking at him

63
Q

When do we experience the highest levels of cortisol?

A

In the morning, just after getting out of bed

64
Q

What are the next steps in investigation after biochemical tests?

A

Imaging e.g. MRI of pituitary

Visual field tests e.g. bitemporal hemianopia means there is compression of the optic chasm

65
Q

How many amino acids in prolactin?

A

199 amino acids

66
Q

Where is prolactin synthesised?

A

Lactotrophe cells of the anterior pituitary gland

67
Q

The secretion of prolactin is under what kind of control?

A

Hypothalamic control by means of Prolactin Release Inhibiting Factor aka DOPAMINE

68
Q

DOPAMINE

A

inhibits prolactin release

69
Q

Thyrotrophin releasing hormone

A

stimulates prolactin release

70
Q

Anti-psychotic medications are

A

dopamine antagonists

71
Q

Therefore anti-psychotic medications e.g. haloperidol

A

induce prolactin secretion

72
Q

Prolactin secretion is stimulated by:

A

Mild stress
Nipple stimulation
Coitus

73
Q

Prolactin inhibits

A

fertility - it is harder to get pregnant whilst breastfeeding

74
Q

What is the primary role of prolactin is to

A

promote lactation and the development of breast tissue

75
Q

Hyperprolactinaemia

A

is the most common cause of infertility

76
Q

A tumour of the pituitary gland which secretes prolactin is called

A

A prolactinoma

77
Q

What happens to prolactin production as we age?

A

It increases

78
Q

Where is growth hormone synthesised?

A

Somatotrophe cells of the anterior pituitary gland

79
Q

Secretion of growth hormone is controlled by?

A

Hypothalamic control via the growth hormone releasing hormone

80
Q

Growth hormone inhibiting hormone is also known as

A

Somatotrophin

81
Q

What has more control in the release of GH - GHRH or GHIH?

A

Growth hormone releasing hormone GHRH

82
Q

Secretion of growth hormone is stimulated by

A

decreased carbohydrates and fatty acids and increased amino acids

83
Q

In some tissues, GH acts via

A

second messengers

84
Q

Where are these second messengers produced?

A

In the liver

85
Q

What are the second messengers produced in the liver called?

A

Insulin-growth-factor 1

Insulin-growth-factor 2

86
Q

What is the function of these second messengers?

A

to promote growth

87
Q

What is the primary effect of GH?

A

to promote linear growth of adolescence by increasing protein synthesis and collagen deposition

88
Q

Growth hormone is also involved in

A

tissue turnover and repair

89
Q

Foetal growth is relatively independent of GH - True or False?

A

True

Endocrinology (11 decks)

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