1b Pituitary Tumours Flashcards
What is a functioning tumour of the somatotrophs called?
Acromegaly
What is a functioning tumour of the lactotrophs called?
prolactinoma
What is a functioning tumour of the Corticotrophs called?
Cushings Disease
What is the name for a radiologically small and large pituitary tumour?
Microadenoma (<1cm) and macroadenoma (>1cm)
What things are we looking for in an MRI?
Seller or suprasellar
Compressing optic chiasm or not
Invading carvenous sinus or not
What are the two functional classifications for tumours?
excess hormone secretion or not (non-functioning adenoma)
Are pituitary tumours generally malignant?
No (<0.5%)
How do you tell the difference between malignant or benign tumour?
Mitotic index measured using Ki67 index - benign is <3%
Pituitary adenomas can have benign histology but display malignant behaviour
Describe how hyperprolactinaemia leads to the associated symptoms?
Prolactin binds to prolactin
receptors on kisspeptin
neurons in hypothalamus
Inhibits kisspeptin release.
Decreases in downstream
GnRH/LH/FSH/T/Oest
Oligo-amenorrhoea/Low
libido/Infertility/Osteoporosis
What is serum prolactin proportional to in prolactinomas?
The size of the tumour
What is the hormonal presentation of prolactinomas?
low GnRH, low FSH and low LH
Usually serum concentration of prolactin >5000mU/L
What are the clinical symptoms of prolactinoma?
Menstrual disturbance
Erectile dysfunction
Reduced libido
Galactorrhoea
Subfertility
What are other causes of elevated prolactin?
Physiological
Pregnancy, stress, nipple stimulation
Pathological
Hypothyroidism, pcos or renal failure
Iatrogenic
Antipsychotics, oestrogen, opiates
Why is prolactin levels higher in pregnancy?
Lactotrophs undergo hypertrophy
Why does primary hypothyroidism cause elevated prolactin?
thyroid gland not working, therefore not producing thyroxine, so TSH rises which stimulates prolactin release
How should a prolactinoma be investigated?
MRI - look for pituitary tumour
What is the first line treatment of prolactinoma?
Cabergoline - dopamine receptor agonist
How do dopamine receptor agonists reduce prolactin and shrink prolactinomas?
Dopamine is the off switch for prolactin, therefore dopamine binds to the D2 receptors on the lactotrophs and reduces prolactin production - can also used dopamine agonists like Cabergoline
Where does the dopamine come from?
The dopaminergic neurones
What is the difference between acromegaly and giganticism?
acromegaly is in adults, gigantism in children
What is the problem with insidious prsentation of acromegaly?
long time between symptoms appearing and mean time to diagnosis
What are some clinical symptoms of acromegaly?
Sweatiness
* Headache
* Coarsening of facial features
* Macroglossia
* Prominent nose
* Large jaw - prognathism
* Increased hand and feet size
* Snoring & obstructive sleep
apnoea
* Hypertension
* Impaired glucose
tolerance/diabetes mellitus
What are the two mechanisms of growth hormone action?
direct and indirect
Direct = growth hormones acting on tissues
Indirect = GH act on liver, which makes IGF-1 which then acts on other body tissues
How do you diagnose acromegaly?
GH pulsatile so random measurement is unhelpful
Failed suppression (‘paradoxical
rise’) of GH following oral
glucose load – oral glucose
tolerance test
Elevated IGF-1
