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Endocrine > The hypothalamus and pituitary > Flashcards

The hypothalamus and pituitary Flashcards

1
Q

How are the hypothalamus and the pituitary connected?

A

The pituitary stalk

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2
Q

What structure comes into close contact with the pituitary that can cause vision changes? Which vision changes are these?

A

The optic nerves in the optic chiasm

Pressure on these can cause bitemporal hemianopnea

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3
Q

Where does the pituitary gland sit?

A

In the pituitary fossa of the sphenoid bone (sella turcica).

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4
Q

How is the pituitary divided?

A

Into anterior adenohypophysis and posterior neurohypophysis

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5
Q

What synthesises posterior pituitary hormones?

A

Supraoptic and paraventricular nuclei in the hypothalamus.

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6
Q

Name the 5 releasing hormones from the hypothalamus

A 
Growth hormone releasing hormone
Prolactin releasing hormone
Thyrotropin releasing hormone
Corticotrophin releasing hormone
Gonadotrophin releasing hormone
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7
Q

Name the 2 inhibitory hormones from the hypothalamus

A

Somatostatin

Dopamine

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8
Q

What does somatostatin do?

A

Suppresses release of growth hormone

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9
Q

What do all hypothalamic hormones have in common (other than dopamine)?

A

They are all peptides

Dopamine is an amine

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10
Q

Name the 6 hormones released from the anterior pituitary ?

A 
Growth hormone
Prolactin
Lutinising hormone
Follicle stimulating hormone
Adrenocorticotrophic hormone
Thyroid stimulating hormone
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11
Q

Name the 2 hormones released by the posterior pituitary

A

Oxytocin

Antidiuretic hormone

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12
Q

What effect does growth hormone have on the body?

A 
It increases plasma glucose levels
Increases protein synthesis
Decreases fat storage
Increases bone growth
Increases soft tissue growth
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13
Q

How does growth hormone increase plasma glucose levels

A

By increasing liver gluconeogenesis and decreasing glucose uptake in cells.

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14
Q

What is IGF-1? And what does it do?

A

Produced by the liver in response to growth hormone.

Acts on the muscle to increase protein synthesis, increases soft tissue and bone growth.

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15
Q

Describe the symptoms and signs of excess growth hormone

A 
Increase in hand and foot size
Increased gap between the teeth
Increased sweating (especially at night)
Prominent supraorbital ridge
Increase in jaw size
Increase in tongue size
Joint pain, lethargy, pain and tingling sensations
Tongue and soft tissue enlargement may cause the patient to start to snore
Polydipsia and polyuria
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16
Q

Why do patients with excess growth hormone get polyuria and polydipsia

A

The increase in glucose in the blood means that they can develop diabetes. The insulin at first accounts for it- however after a while the receptors become desensitised and type 2 diabetes ensues.

17
Q

What are the complications of excess growth hormone?

A

Type 2 diabetes
High bp- increase in free fatty acids means patient is at higher risk of atherosclerosis
Carpal tunnel syndrome due to increase in growth of soft tissues.

18
Q

What is the most likely cause of hyper secretion of growth hormone?

A

Pituitary adenoma

19
Q

What is acromegaly?

A

Hypersecretion of growth hormone from the pituitary gland.

Could be due to a micro adenoma <1cm or a macro adenoma >1cm

20
Q

What is gigantism?

A

Hypersecretion of growth hormone in children. In childhood- the epiphyseal growth plates haven’t fused yet so excess growth hormone release causes accelerated growth of long bones.

21
Q

Why can’t gigantism occur in adults?

A

This can’t occur in adults due to the epiphyseal growth plates already being fused.

22
Q

Symptoms of a pituitary tumour

A

Can cause local symptoms as well as those produced from excess release of hormone.
Headache
Bitemporal hemianopia
Hormone release- in 1/3rd of people it also causes hypersecretion of prolactin.
Suppress normal pituitary function- hypopituitism

23
Q

Investigations into acromegaly

A 
Oral glucose tolerance test
IGF-1 test
Visual field exam
MRI
Pituitary function tests
Look at old photos and compare
24
Q

Oral glucose tolerance test

A

Growth hormone causes an increase in plasma glucose levels. Therefore when plasma glucose levels are high- growth hormone becomes suppressed. This doesn’t happen in acromegaly- so by giving oral glucose at 9am and testing the patients growth hormone levels every half an hour for two hours you can see whether the growth hormone becomes suppressed.
Normal levels <1ug/L
Acromegaly levels>1ug/L

25
Q

IGF-1 test

A

Gives an idea of the mean growth hormone secretion in the past 24 hours.
Normal levels of this and normal levels of growth hormone can rule out acromegaly.

26
Q

What benefits come from doing an MRI on a patient with suspected acromegaly?

A

You can assess whether it is a micro adenoma or macro adenoma.

27
Q

Why would you look at pituitary function tests in a patient with suspected acromegaly?

A

Other pituitary hormones may be suppressed because of the tumour.

28
Q

Treatment of acromegaly

A

Trans-sphenoidal surgery
Radiotherapy
Medical therapy

29
Q

Advantages of surgery

A

Generally first line treatment

Can cause remission in many cases

30
Q

Advantages and disadvantages of radiotherapy

A

Advantage- success rate at 25% after 3 years
Can be used on its own or as add on therapy to surgery
Disadvantages- treatment only prevents growth of the tumour- may still get local symptoms
Also takes a LONG time- up to 10 years.
Patient may also suffer from hypopituitism as a result.

31
Q

Name the medical therapies and describe them

A

Dopamine agonists- used to suppress the secretion of prolactin
Somatostatin receptor agonists- increase levels of somatostatin to deal with increased levels of growth hormone. Called octreotide or lanreotide
Growth hormone antagonists- act on growth hormone receptors around the body to de-sensitise them. Called Pegvisomant

Endocrine (20 decks)

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