Endo - Pituitary Tumours Flashcards
What is functioning tumour of somatotrophs called?
Acromegaly
What is functioning tumour of lactotrophs called?
Prolactinoma
What is functioning tumour of gonadotrophs called?
Gonadotrophinoma
What is functioning tumour of thyrotrophs called?
TSHoma
What is functioning tumour of corticotrophs called?
Corticotroph adenoma
What are the 3 criteria for classifying pituitary tumours?
Function
Size
Benign vs malignant
What is a functioning tumour?
Secretes excess hormone
What is a non functioning pituitary adenoma?
Doesn’t secrete excess
What is a micro adenoma?
<1cm
Sellar
What is a macro adenoma?
> 1cm
Suprasellar
What other 2 questions do we need to ask when assessing tumour size?
Is it compressing on the optic chiasm?
Is it invading the cavernous sinus?
What is the risk when a tumour has invaded the cavernous sinuses?
There are to many cranial nerves and the internal carotid therefore removing a tumour in the cavernous sinus is too risky
How do we determine whether a tumour is malignant or benign?
Determined by mitotic index by ki67 index - if it is less than 3% then it’s benign
When may a benign tumour have malignant behaviour?
For example, if it causing a visual disturbance
Describe the secretion pattern of GnRH
Pulsatile
How does hyperprolactinemia cause hypogonadism?
Prolactin binds to prolactin receptors on kisspeptin neurones which inhibits the release of GnRh therefore we inhibit the release of FSH and Lh in turn causing T or Oestrogen to fall
What is the commonest functioning pituitary adenoma?
Prolactinoma
What is the normal range of prolactin?
<300 M mU/L
<600 F mU/L
What is the prolactin level in a prolactinoma?
> 5000 mU/L
What increases serum prolactin?
Increase in tumour size
What is the presentation in a prolactinoma?
Menstrual disturbance Erectile dysfunction Low libido Galactorrhoea Subfertility
What are the 3 classes of causes for hyperprolactinemia?
Physiological
Pathological
Iatrogenic
What are physiological causes of increased PRL?
Prengancy/breast feeding
Stress: exercise, seizure, venepuncture
Nipple/chest wall stimulation
What are the pathological causes of increased PRL?
Primary hypothyroidism
PCOS
Chronic renal failure (PRL not excreted properly)
What are the iatrogenic causes of increased PRL?
Anti-psychotic SSRI Anti-emetics High dose oestrogen Opiates
When should we consider other differentials aside from prolactinoma when looking at an increased PRL?
When we have confirmed it is a true elevation not a false positive
If there are not 2 clinical features of prolactinoma and we’ve checked the drug chart
What do we consider after ruling out PRL?
Macroprolactin
Stress to venepuncture
What is macroprolactin?
Most prolactin is monomeric however in some people PRL will clump together and stick to IgG therefore during a blood test this will show up as high PRL - benign blood test error
What is the stress response to venepuncture?
Prolactin secreted in response to stress therefore we take patient to a relaxing unit and place needle in their arm for a long period, measuring PRL every 20 minutes waiting for PRL to fall
What should we do if we have rules out macroprolactin and stress for venepuncture?
Order a pituitary MRI
What is the first line treatment for prolactinoma?
DA receptor agonist such as cabergoline to normalise serum prolactin
Is cabergoline safe fro pregnant women?
Yes
When do we increase the dose of cabergoline?
When there is a bigger tumour
How does cabergoline work?
Binds to D2 receptors on lactotrophs therefore stimulates the inhibitory effect they have on PRL secretion, and there is less PRL secretion
What do we call a functioning Gh tumour in children?
Gigantism
What do we call a functioning GH tumour in adults?
Acromegaly
What is the onset of acromegaly and how does this affect its presentation as a tumour?
Insidious onset (10 years) therefore often reveals as a big tumour
What are the symptoms of acromegaly?
Sweatiness Headache Coarsening of facial features Spade like hands due to increased soft tissue size Large jaw (prognathism) Increase in foot and hand size Snoring/OSA Hypertension Impaired glucose tolerance/ diabetes mellitus
How does acromegaly cause headaches?
Due to IGF-1/GH behaviour, not because of tumour size
Why do we not measure GH to diagnose acromegaly?
GH is too pulsatile
How do we diagnose acromegaly?
Increased IGF-1 serum level with failed suppression test after 75g glucose load, instead a paradoxical rise is seen
What may we also see in acromegaly patients in terms of other hormones?
Increase in prolactin
What should we do after confirming excess GH?
Pituitary MRI
What is the first line treatment for acromegaly?
Surgery: trans-sphenoidal pituitary surgery due to increased CVD risk
What should we do prior to acromegaly surgery?
Somatostatin analogue e.g. ocreotide injection
What is a side effect of octreotide injection?
Endocrine cyanide therefore can disturb gut enzymes to cause diarrhoea
Why do GH tumours co-secrete PRL?
Some GH tumours have D2 receptors
When else may drugs be used for a GH tumour?
If surgical resection is incomplete
What is the con of using radiotherapy for Gh tumour?
Slow
What happens in Cushings syndrome?
Too much cortisol
What is the difference between Cushing’s syndrome and disease?
Cushing’s syndrome is when there is too much cortisol from any cause
Cushing’s disease is when there is a tumour causing increased ACTH therefore increased cortisol
What are the causes of Cushing’s syndrome?
Too much steroids
Adrenal adenoma
What are the causes of Cushing’s disease?
Corticotroph adenoma
Ectopic ACTH e.g. from lung cancer
How do we show Cushing’s on a test?
We want to demonstrate that we have either lost diurnal cortisol rhythm or we can show that we have produced too much cortisol over a 24 hours period
Where can we test for cortisol?
Can be tested for in the saliva or the blood
What can we use to try and suppress cortisol?
We can give oral dexamethasone which is an exogenous glucocorticoid
What should we do once hypercortisolism is confirmed?
Measure ACTH - if that is high then we order a pituitary MRI
What do non functioning pituitary adenomas secrete?
They do not secrete any specific hormone
What do non functioning pituitary adenomas cause?
Often cause a visual disturbance such as bitemporal hemianopia
What may non functioning pituitary adenomas cause?
As they get larger they may disrupt the stalk and thus cause hypopituitarism
What is an exception to adenomas causing hypopituitarism?
Inhibitory dopamine won’t be able to travel down the stalk therefore we may get hyperprolactinemia