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Endocrinology > Acromegaly and Prolactinoma > Flashcards

Acromegaly and Prolactinoma Flashcards

1
Q

When will getting acromegaly make you a giant?

A

Teenager

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2
Q

Pathogenesis of acromegaly

A

Pituitary Tumour – releases GH – under influence of GH binding to receptor in liver get release of Insulin like growth factor 1 – this goes on to have systemic efffects
GH in excess causes harm

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3
Q

Is acromegaly common?

A

No
Incidence of 3.3 per million (range 2.8 to 4.0)
Mean age at diagnosis is 44 years

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4
Q

What are the co-morbidities of acromegaly?

A

Hypertension and heart disease
High BP
Cerebrovascular events and headache
Strokes
Arthritis
Insulin-resistant diabetes
Sleep apnea

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5
Q

What is the impact of acromegaly on survival?

A

Affects your LE
However this + diabetes or cardiac disease brings it down exponentially lower

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6
Q

Growth hormone (acromegaly) and survival

A

As growth hormones level increase survival was lower
IGF one stimulated by GH – fairly stable – increased of this leads to increased mortality

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7
Q

What do we have to check for the diagnosis of acromegaly?

A

Clinical Features
GH
IGF-I

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8
Q

What are the physical features of acromegaly?

A

Acral enlargement
Arthralgias
Maxillofacial changes
Excessive sweating
Headache
Hypogonadal symptoms

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9
Q

What are the GH secretion patterns?

A

Growth hormone is a pulsatile hormone – in normal people theres pulses of GH and then go down to baseline
Acromegaly – GH never returns fully to baseline

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10
Q

What is the oral glucose tolerance test for the diagnosis of acromegaly?

A

Normal – give them glucose it suppresses GH
Acromegaly don’t get suppression – get rise instead (most of the time) dont get suppression

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11
Q

What is the criteria for the diagnosis of acromegaly?

A

Acromegaly excluded if:
random GH <0.4 ng/ml and normal IGF-I
If either abnormal proceed to:
75 gm Glucose tolerance test (GTT)
Acromegaly excluded if:
IGF-I normal and
GTT pushes GH down

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12
Q

What are the options for treatment for acromegaly?

A

Pituitary surgery

Medical therapy

Radiotherapy

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13
Q

Why is surgery a good option for acromegaly?

A

Causes rapid fall of GH
Decompression
Cost effective
Prospective cure

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14
Q

Surgery rates

A

For a microadenoma <1cm 90% success rate
For a macroadenoma >1cm <50cm success rate
Depends on surgeon and size of tumour

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15
Q

Whats transsphenoidal pituitary surgery?

A

Used as primary treatment for all types of pituitary adenoma except prolactinoma
Problems making surgery harder

Large size
Invasiveness

Life-long monitoring needed for most patients

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16
Q

How does conventional radiotherapy work for acromegaly?

A

multi-fractional
Optic chiasm doesn’t like radiotherapy
Fraction – small dose daily for 5-6 weeks – irradiates tumour – minimise the dose of optic chiasm – this is conventional
Stereotactic – focusing radiotherapy to make sure it misses vital structures

17
Q

What is stereostatic radiotherapy?

A

single fraction
less radiation to surrounding tissues
gamma knife
LINAC
proton beam
Gamma knife – 200 fine beams to hit a target

18
Q

What are the possible issue of pituitary radiotherapy?

A
  • Loss of pituitary function in the long-term
  • Potential damage to local structures – e.g. eye nerves
  • Control of tumour growth / excess hormone
    secretion not always achieved
  • Life-long monitoring needed for all patients
19
Q

What are the disadvantages of convential radiotherapy?

A
  • Delayed response
  • Hypopituitarism
  • Rare secondary tumours
  • rare visual defects
  • Long time to take its effects

Deficiency at 10 years:
TSH 19%
ACTH 38%
gonadotrophin 55%

20
Q

What does the medical therapy consist of?

A

Dopamine agonists – cabergoline
Somatostatin analogues
Growth Hormomne receptor antagonist

21
Q

What do pituitary tumours express?

A

Tumours express D2 receptors – G protein coupled cell surface receptors and under influence of dopamine will switch off GH

22
Q

What do dopamine agonists do?

A

Control normal IGF-1
bromocriptine 10%
Cabergoline 37%
more potent
fewer side effects
twice weekly
Particularly useful in GH/prolactin co-secreting tumors
occasional dramatic tumour shrinkage
control of GH secretion

23
Q

What are the advantages of dopamine agonists (medical therapy)?

A

No hypopituitarism
Oral administration
Rapid onset

24
Q

What are the disadvantages of dopamine agonists (medical therapy)?

A

Relatively ineffective
Side effects

25
Q

Somatostatin

A

Endogenous hormone
Short half life
Hormone cyanide – switches off production of many diff hormones
Subtype 2 typically present on growth hormone secreting tumours that cause acromegaly
binds all 5 receptor sub-types

26
Q

Somatostatin analogues

A

Octreotide
more specific
T1/2 100 min
no rebound

Lanreotide
Both of these share same business end of molecule compared to somatostatin

27
Q

Disadvantages of somatostatin analogues

A

injectable
side effects

28
Q

Pegvisomant

A

GH analogue
191 amino acids
9 amino acid substitutions
4 - 5 PEG moieties
molecular weight 42 - 46000 D
half-life >70 hours
subcutaneous administration
serum GH cannot be used as a disease marker

29
Q

What is the physiology of pegvisomant?

A

GH binds to cytokine receptor – binds at site 1 – site 2 causes dimerization to have this dimer that then signals allow GH in liver to cause creation of IGF 1 and signalling Mutation which at site 2 prevents the dimerization and some mutation in site 1 to make it more avidly bind to GH receptor – pegalation molecules added to it so it doesn’t clear as quickly – works as competitive antagonist

30
Q

Pegvisomant results

A

Very good
97% normalisation of IGF-1

31
Q

Prolactinoma features

A

Incidence 10 per 100,000
Women&raquo_space; men
Prevalence 90 per 100,000

Lactotroph cell tumour of the pituitary

32
Q

What are the clinical features of microadenoma

A

headache
visual field defect (bi-temporal hemianopia)
CSF leak (rare)

33
Q

What are the clinical features of the effect of prolactin?

A

menstrual irregularity/amenorrhoea
infertility
Galactorrhoea
low libido
low testosterone in men
High levels of prolactin interferes with gonadotrophin releasing hormone pulsatitlity and switches off synchronised release of FSH and LH
Galactorrhoea – milk from nipple

34
Q

Hyperprolactinaemia features:

A

Macroprolactinoma – can be massive

Microprolactinoma – virtually always stay small

Non functioning pituitary tumour – compression of pituitary stalk – prolactin <4000 mIU/L

Antidopaminergic drugs – don’t measure prolactin in patients on these, but a careful drug history needed!

35
Q

What is the management of prolactinoma

A

Medical rather than surgery
Dopamine agonists – cabergoline, bromocriptine, quinagolide

Remarkable shrinkage usual with macroadenoma – sight saving

Microadenoma - usually respond to small doses of cabergoline just once or twice per week

Endocrinology (17 decks)

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