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endo > 1B pituitary tumours > Flashcards

1B pituitary tumours Flashcards

1
Q

What would a tumour of somatotrophs cause?

A

Acromegaly

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2
Q

What would a tumour of lactotrophs cause?

A

Prolactinoma

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3
Q

What would a tumour of thyrotrophs cause?

A

TSHoma

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4
Q

What would a tumour of gonadotrophs cause?

A

Gonadotrophinoma

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5
Q

What would a tumour of corticotrophs cause?

A

Cushing’s disease (corticotroph adenoma)

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6
Q

What are the different ways to classify a pituitary tumour?

A
  • Radiological (MRI)
  • Function
  • Benign or malignant
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7
Q

What are the subclassifications of radiological (MRI) scans for pituitary tumours?

A
  • Size- microadenoma is <1cm and macroadenoma is >1cm
  • Sellar or suprasellar (grows out of sella turcica)
  • Compressing optic chiasm or not
  • Invading cavernous sinus or not
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8
Q

What are the function subclassifications?

A
  • Excess secretion of a specific pituitary hormone e.g. prolactinoma
  • No excess secretion of pituitary hormone (non functioning adenoma)
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9
Q

How are pituitary tumours classified as benign or malignant?

A
  • Pituitary carcinoma- very rare (<0.5% of pituitary tumours)
  • Mitotic index measured using Ki67 index- <3% means tumour is benign
  • Pituitary adenomas can have benign histology but display malignant behaviour
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10
Q

What would hyperprolactinaemia caused by a prolactinoma do to HPG axis?

A
  • PRL binds to PRL receptors on kisspeptin neurons in hypothalamus
  • Inhibits kisspeptin release
  • Decreases in downstream GnRH → LH/FSH → T/Oest
  • Oligo-amenorrhoea/low libido/infertility/osteoporosis
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11
Q

What do prolactinomas do to serum PRL?

A
  • Commonest functioning pituitary adenoma
  • Usually serum PRL >5000 mU/L
  • Normal levels: 530mU/L
  • Serum PRL proportional to tumour size
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12
Q

How does hyperprolactinaemia caused by a prolactinoma present?

A
  • Menstrual disturbance
  • Erectile dysfunction
  • Reduced libido
  • Subfertility
  • Galactorrhoea (milk production outside of breastfeeding- men can also get galactorrhoea but unusual)
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13
Q

What are other causes of elevated PRL aside from a prolactinoma?

A
  • Physiological
    • Pregnancy/breastfeeding
    • Stress: exercise, seizure, venepuncture
    • Nipple/chest wall stimulation
  • Pathological
    • Primary hypothyroidism
    • PCOS
    • Chronic renal failure
  • Iatrogenic
    • Antipsychotics
    • Anti-emetics
    • Opiates
    • Selective serotonin reuptake inhibitors (SSRIs)
    • High dose oestrogen
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14
Q

What is a true elevation in serum PRL and why is it important to get?

A
  • No diurnal variation, not affected by food
  • Confirm true elevation in serum PRL as there are many false positives
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15
Q

What could it be when you see a mild elevation in serum PRL but no clinical features of prolactinoma and you’ve checked the medication list?

A
  • Macroprolactin
  • Venepuncture
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16
Q

What is macroprolactin?

A
  • Majority of circulating PRL is monomeric and biologically active
  • Macroprolactin is a ‘sticky’ polymeric form of PRL that is an antigen-antibody complex of monomeric PRL and IgG (normally <5% of circulating PRL)
  • Recorded on assay as elevation of PRL- needs alternative method to confirm
  • Limited bioavailability and bioactivity
  • Can reassure patient
17
Q

How do we deal with stress of venepuncture?

A

By a cannulated PRL series:

Sequential serum PRL measurement 20 mins apart with an indwelling cannula to minimise venepuncture stress

18
Q

What do you do if you’ve confirmed a true pathological elevation of serum PRL?

A

Organise a pituitary MRI

19
Q

How do we treat prolactinomas?

A
  • First-line treatment is medical not surgical
  • Dopamine receptor agonists are mainstay of treatment like cabergoline (bromocriptine)
  • Safe in pregnancy
  • Aim is to normalise serum PRL and shrink prolactinoma
  • Microprolactinomas need smaller doses than macroprolactinomas
20
Q

How do dopamine receptor agonists work?

A

1) The agonist mimics dopamine and it binds to D2 receptors on anterior pituitary lactotrophs

2) Works like dopamine and prevents lactotrophs making PRL

21
Q

What are the symptoms of acromegaly?

A
  • Sweatiness
  • Headache
  • Coarsening of facial features- macroglossia, prominent nose
  • Large jaw- prognathism
  • Increase hand and feet size
  • Snoring and obstructive sleep apnoea
  • Hypertension
  • Impaired glucose tolerance/diabetes mellitus
22
Q

How do we diagnose acromegaly?

A
  • GH is pulsatile- so random measurement is unhelpful
  • Elevated serum IGF-1 helps
  • Failed suppression (paradoxical rise) of GH following oral glucose load- oral glucose tolerance test- we don’t know why
  • PRL can be raised- co-secretion of GH and PRL
23
Q

What do we do once we confirm GH excess for acromegaly?

A

Pituitary MRI to visualise pituitary tumour

24
Q

Why do we need to treat acromegaly?

A

Increased cardiovascular risk in untreated acromegaly

25
Q

What is the treatment for acromegaly?

A
  • First line treatment is surgical- trans-sphenoidal pituitary surgery
  • Aim to normalise serum GH and IGF-1
  • Could use radiotherapy (slow)
26
Q

What can we use to shrink tumour prior to surgery for acromegaly?

A
  • Somatostatin analogues e.g. octreotide- ‘endocrine cyanide’
  • Dopamine agonists e.g. cabergoline (GH secreting pituitary tumours frequently express D2 receptors)
27
Q

What is Cushing’s syndrome?

A

Occurs due to an excess of cortisol or other glucocorticoid

28
Q

What are the causes of Cushing’s syndrome?

A

ACTH independent

  • Taking steroids by mouth (common)
  • Adrenal adenoma or carcinoma

ACTH dependent

  • Cushing’s disease (corticotroph adenoma)
  • Ectopic ACTH (lung cancer)
29
Q

Difference between Cushing’s disease and syndrome?

A
  • Syndrome: excess cortisol
  • Disease: corticotroph adenoma secreting ACTH
30
Q

What investigations are performed for Cushing’s?

A
  • Elevation of 24h urine free cortisol- increased cortisol secretion
  • Elevation of late night cortisol- salivary or blood test- loss of diurnal rhythm
  • Failure to suppress cortisol after oral dexamethasone (exogenous glucocorticoid)- increased cortisol secretion
31
Q

Once hypercortisolism is confirmed, what further investigations are made?

A

Measure ACTH and if it’s high, do a pituitary MRI scan to find tumour

32
Q

What do non-functioning pituitary adenomas often present with?

A

Bitemporal hemianopia

33
Q

What problems can non-functioning pituitary adenomas cause?

A
  • Can present with hypopituitarism
  • Serum PRL can be raised (dopamine can’t travel down pituitary stalk from hypothalamus)- this is because tumour compresses/pinches posterior pituitary stalk
34
Q

How do we treat larger pituitary tumours?

A

Trans-sphenoidal surgery needed for larger tumours, particularly if visual disturbance

endo (12 decks)

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