Pituitary tumours Flashcards
WHat re the 5 cells in the anterior pit and what hormones do they make
Somatotrophs --> GH/ somatostatin Lactotrophs --> prolactin Thyrotropes --> TSH / thyrotropin Gonadotrophs --> LH + FSH corticotrophs -->ACTH / corticotrophin
What do you call each each of the 5 anterior pit cells if they make to much hormone
Somatotrophs --> acromegaly lactotrophs --> prolactinoma thyrotropes --> TSHoma Gonadotrophs --> gonadotrophin Corticotrophs --> Cushing's disease ( corticotroph adenoma)
3 ways to classify pit tumours
1) radiological –> can classify on size: micro ( <10nm) or macro(>10nm) adenoma. Or can classify on sellar / suprasella , compressing optic chiasm or not, invading carvernous sinous or not
2) Function –> functional ( secrete excess hormone) vs non functional ( doesn’t)
3) Benign or malignant –> measure mitotic index note pituitary adenomas can be benign but display malignant behaviour
What mitotic index is measured for benign / malignant pit tumour classification
ki67
What does hyperprolactinaemia do and why
cause amenorrhea / low libido/ infertility / osteoporosis
why:
prolactin binds to receptors on kisspeptin neurons in hypothalamus –> inhibits kisspeptin release –> decrease in downstream GnRH/LH/FSH/oest
how to define prolactinoma clinically
Serum prolactin over 5000mU/l
most common pit tumour
Symptoms of prolactinoma
Menstrual disturbance
erectile dysfunction
reduced libido
galactorrhoea ( milky discharge from nipple)
Subfertility ( due to no GnRH for LH/FSH)
Other causes of elevated prolactin
1) physiological –> pregnancy / breastfeeding , stress , excurse, seizure , !venepuncture due to stress
nipple chest wall stimulation
2) pathological –> 1ary hypothyroidism , Polycystic ovarian syndrome , chronic renal failure
3) Iatrogenic –> antiphycotics, selective serotonin reuptake inhibitors, anti- emetics , high dose oestrogen , opiates
4) !Macroprolactin
What can prolactin levels be used to daignose
True seizure vs stress seizure
What is the process for diagnosing hyperprolactinaemia
Confirm true elevation in serum prolactin ( lots of false positives) however prolactin is not affected by food or diurnal variation
See hyperpro is mild or severe –> in mild patients ( if no clinical features consistent and medication list reviewed think of 2 other possible options
in true elevation –> arrange MRI of pit
What is macroprolactin
sticky polymeric form on prolactin - formed from antigen - antibody complex of monomeric prolactin and IgG
will elevate serum prolactin levels thus needs more investigation
but patient is normal and can be reassured
how can you exclude a raised prolactin level due to venepuncture
insert a cannula to measure prolactin every 20 min . If due to venepuncture after a while prolactin levels will decrease
How to treat prolactinomas
Use dopamine receptor agonists , cabergoline –> these will shrink prolactinoma and normalise serum prolactin
these are safe in pregnancy but remember different dose will be needed depending on size of pit tumoour
How do dopamine receptor agonists work
Bind to D2 receptors and act like dopamine released from dopaminergic neurons in hypothalamus. This blocks prodcution of prolactin
What is the name of the disease for too much GH in children vs in adults
Gigantism ( due to unfused epiphyseal plate) and acromegaly
Symptoms of acromegaly
slow presenting
Insidious presentation: ( long time to present). mean time to diagnosis from onset of symptoms = 10 years
•Sweatiness
•Headache
•Coarsening of facial features: macroglossia and prominent nose
•Large jaw - prognathism
•Increased hand and feet size
•Snoring & obstructive sleep apnoea ( due to enlarged tissue around larynx and pharynx)
•Hypertension
•Impaired glucose tolerance/diabetes mellitus
What goes GH act on
Body tissues for metabolic actions for growth and development
liver to prod IGF -1 and 2 ( somatomedin)
How to diagnose acromegaly
GH pulsitile so can’t measure
elevated serum igf-i
Growth hormone exerts anabolic effects on the growth of tissues (muscle and bone) supporting the development of an individual.
Potentiates the release of insulin-like growth factor (Somatomedin) – IGF-I and IGF-2 from the liver.
paradoxical (failed to suppress) rise of GH following oral glucose tolerance test
high prolactin
this is co secreted with GH
Cannot confirm acromegaly by itself
pituitary MRI to visualise tumour
How do we treat acromegaly
surgery ( trans sphenoidal pit surgery) –> first line, aims to normalise serum GH and IGF-1
can use medical treatment prior to surgery to shrink tumour of if surgical resection incomplete
2) Somatostatin analogues ie octreotide ( endocrine cyanide as targets all cells)
3) Dopamine agonists eg cabergoline ( GH tumours freuq express D2 receptors
4) radiotherapy ( slow)
What happens if we don’t treat acromegaly
Increased Cardiovascular risk
Symptoms of cushing’s
Red cheeks ,
mental changes ( depression ), osteoporosis , fat pads ( buffalo hump), thin skin , moon face , easy bruising , purple striae ( stretch marks)
Impaired glucose tolerance ( diabetes) + hypertensive
proximal myopathy ( weakness muscles and thin arms and legs)
Poor wound healing , pendulous abdomen
What causes cushings
Excess cortisol / other glucocorticoid due to :
ACTH dependent reasons :
1) Pit adenoma ( corticotroph adenoma) ( pit dependent Cushing’s disease) aka secreting too much ACTH ( common)
3) Ectopic ACTH ( lung cancer)
ACTH independednt reasons:
1) taking steroids
4) Adrenal adenoma / carcinoma
How to diagnose cushings’
Elevation of 24h urine free cortisol
Elevation of late night cortisol ( salivary or blood test) due to loss of diurnal rhythm
Failure to supress cortisol after oral dexamethasone ( exogenous glucocorticoid) increased cortisol secretion
once confirmed hypercortisolism measure ACTH. If high –> pituitary MRI + most likly ACTh dependent cause
Symptoms of non-functioning pit adenomas
bitemporal hemianopia , but no secretion of specific hormone
can present with hypopituitarism
and raised serum prolactin ( due to blockage of pit stalk so no dopamine can travel down from hypothalamus to inhibit prolactin )
