Pituitary Tumors Flashcards
What are the 5 anterior pituitary cell types?
Somatotrophs Lactotrophs Thytotrophs Gonadotrophs Corticotrophs
What does a tumour of somatotrophs cause?
Acromegaly
Too much GH
What does a tumour of lactotrophs cause?
Prolactinoma
Too much prolactin
What does a tumour of thyrotrophs cause?
TSHoma
Very rare
What does a tumour of gonadotrophs cause?
Gonadotrophinoma
Very rare
What does a tumour of corticotrophs cause?
Cushing’s disease
(Corticotroph adenoma)
Too much ACTH therefore too much cortisol
What is the difference between Cushing’s syndrome and disease?
Disease = corticotroph adenoma
How do we classify pituitary tumour radiologically?
Size
Sellar or Suprasellar
Compressing optic chiasm or not
Invading cavernous sinus or not
What how do we classify pituitary tumour by size?
Microadenoma (<1cm)
Macroadenoma(>1cm)
What is a functional pituitary tumour?
Excess secretion of a specific pituitary hormone
e.g. prolactinoma
What is a non functional pituitary tumour?
No excess secretion of pituitary hormone
Non-functioning Adenoma
Is pituitary cancer common?
Pituitary carcinoma very rare
Mitotic index measured using Ki67 index - benign is <3%
Are pituitary tumours benign or malignant?
Pituitary adenomas can have benign histology but display malignant behaviour
How does hyperprolactinaemia shut down the HGP axis?
Prolactin binds to prolactin receptors on kisspeptin neurones in hypothalamus
Inhibits kisspeptin release
Decreases in downstream GnRH
Decreased LH/FSH
Decreased Testosterone and Oestrogen
Causes oligo-amenorrhoea, low libido, infertility and osteoporosis
What is the most common functional pituitary tumour?
Prolactinomas
What is the serum prolactin proportional to?
Tumour size
>5000mU/L
How does a prolactinoma present?
Menstrual disturbance Erectile dysfunction Reduced libido Galactorrhea (milk production from the breast) Sub-fertility
What are the physiological causes of an elevated prolactin?
Pregnancy/breastfeeding
Stress: exercise, seizure, venepuncture
Nipple/chest wall stimulation
What are the pathological causes of an elevated prolactin?
Primary hypothyroidism
Polycystic ovarian syndrome
Chronic renal failure, prolactin secreted by the kidneys and cannot be excreted
What are the iatrogenic causes of an elevated prolactin?
Antipsychotics
Selective serotonin re-uptake inhibitors
Anti-emetics
(all work by dopaminergic pathway which inhibits prolactin)
High dose oestrogen
Opiates e.g. morphine
Can prolactin levels vary in a day?
No diurnal variation
Not affected by food
What do you consider if someone has a mild prolactin elevation, no clinical features and you have reviewed their medication list?
Macroprolactin
Stress of venipuncture
What is macroprolactin?
‘sticky prolactin’
a polymeric form of prolactin
an antigen-antibody comped of monomeric prolactin and IgG (normally <5% of circulating prolactin
Recorded on assay as elevation
No impact on life
Can reassure patient
How do you exclude the stress of venepuncture?
Cannulated prolactin series
Sequential serum [prolactin] measurement 20 mins apart with an indwelling cannula to minimise venipuncture stress
When do you conduct a pituitary MRI?
Only once you have confirmed a true pathological elevation of serum prolactin
What is the first line treatment of prolactinoma?
Medical not surgical
Dopamine receptor agonists mainstay of treatments
Cabergoline
Safe in pregnancy
Aims to normalise serum prolactin and shrink prolactinoma
How do dopamine receptor agonists work?
Dopamine from hypothalamic dopaminergic binds to receptor and inhibits prolactin
D2 agonists do the same
What is the difficulty with acromegaly?
Often insidious presentation
Mean time to diagnosis from onset of symptoms = 10y
What are the symptoms of acromegaly?
Sweatiness
Headache
Coarsening of facial features - macroglossia - prominent nose Large jaw - prognathism Increased hands and feet Snoring and obstructive sleep apnea Hypertension Impaired glucose tolerance/ diabetes mellitus
What is are the two mechanism of GH?
Via IGF-1 on the liver
Directly on muscle and bone
How do we diagnose acromegaly?
GH pulsatile -so random measurement unhelpful
Elevated serum IGF-1
Failed suppression (paradoxical rise) of GH following oral glucose load tolerance test
Prolactin can be raised (co-secretion of GH and prolactin)
Carpal tunnel syndrom
What is done once GH is confirmed to be in excess?
Pituitary MRI to visualise pituitary tumour
How doe we treat acromegaly?
First line treatment is surgery
Trans-sphenoidal pituitary surgery
Aim to normalise serum GH and IGF-1
What can you do to treat acromegaly medically?
Medical treatment prior to surgery to shrink tumour or if resection is incomplete
Somatostatin analogues
Dopamine agonists
Radiology (very slow)
What are the symptoms of Cushing’s?
Mental changes Red cheeks Moon face Easy brushing Lemon on a stick etc.
What causes Cushing’s?
Oral steroids
Pituitary depende Cushing;s disease (pituitary adenoma)
Ectopic ACTH (lung cancer)
Adrenal adenoma or carcinoma
How do you investigate Cushing’s disease?
Elevated of 24h urine free cortisol - increased cortisol secretion
Elevation of late nigh cortisol - salivary or blood test - loss of diurnal rhythm
Failure to suppress cortisol after oral dexamethasone (exogenous glucocorticoid) - increased cortisol secretion
What are non-functioning pituitary adenomas?
Don’t secrete any specific hormone
Often present with visual disturbance (bitemporal hemianopia)
How can someone with a non-functioning pituitary adenoma present?
Hypopituitarism
Serum prolactin can be raised
(dopamine cannot travel down pituitary stalk from hypothalamus)
How can you treat non-functioning pituitary adenomas?
Trans-sphenoidal surgery needed for larger tumours, particular if visual disturbance
3rd line: Sellar radiotherapy
