Pituitary Flashcards
What are the 6 hormones produced by the anterior pituitary?
GH Prolactin TSH LH, FSH ACTH
What hormone stimulates GH production?
GHRH
What hormone stimulates /suppresses prolactin?
TRH stimulates
dopamine suppresses
What hormone stimulates LH, FSH
LHRH
What hormone stimulates ACTH?
CRH
Why do people with hypothyroidism commonly have hyperprolactinaemia?
Low T4 > positive feedback onto TRH > high TRH
TRH also stimulates prolactin
What are symptoms of hyperprolactinaemia?
galactorrhea
amenorrhoea
What types of prolactinoma can you get in terms of size?
micro adenoma = <1cm
macro adenoma = >1cm
What visual field defect is caused by a prolactinoma?
Bilateral hemianopia
Due to compression of optic chiasm
What visual testing is done for bilateral hemianopia?
Humphreys test
When is a prolactinoma considered inoperable?
when it is in very close contact with the carotid arteries
Define prolactinoma
An adenoma of the pituitary producing excess prolactin
What prolactin results do you get with a prolactinoma?
x10 higher than upper limit for prolactin
so 6000
What testing is important if a prolactinoma is suspected
Testing pituitary to see if it responds to metabolic stress by producing ACTH, GH
so perform a COMBINED PITUITARY FUNCTION TEST -
What does a CPFT involve?
Give 3 stimuli:
- hypoglycaemia
- TRH
- LHRH
What must you be aware of before performing a CPFT ‘
That hypoglycaemia is DANGEROUS
Therefore ensure that there are no cardiac RF (ECG normal) and no history of epilepsy
What occurs to the patient when blood glucose drops below 1.5 mol/L
Neuroglycopoenia - patient loses consciousnes, becomes confused or aggressive
How do you rescue a patient with severe hypoglycaemia?
50mL 20% dextrose IV
What is the dose of insulin you must give in CPFT?
0.15 units/kg
What hormone must be replaced urgently if ALL pituitary hormones are reduced?
HYDROCORTISONE
To replace cortisol
What cortisol levels need to be reached for a CPFT to be normal?
Cortisol >550
What GH levels need to be reached for a CPFT to be normal?
GH >10
What hormones need to be given if pituitary function is suppressed?
hydrocortisone
Thyroxine
Oestrogen
GH
What is front line treatment for a prolactinoma?
A dopamine agonist (bromocriptine/cabergoline)
This willl shrink the size of the tumour
Other than a prolactinoma, what other tumour can cause increased prolactin?
a LARGE NON FUNCTIONING tumour
How does a large non functioning tumour cause hyperprolactinaemia?
It compresses the pituitary stalk
Thereby prevents dopamine from reaching the pituitary
How do you treat a large non functioning tumour?
SURGERY
They will NOT respond to dopamine agonist
How do you distinguish a prolactinoma from a non functioning tumour?
SIZE & PROLACTIN RATIO
A LARGE non functioning tumour (size detected by bitemporal hemianopia) will cause moderate increase in prolactin (around 3000)
A SMALL prolactinoma can cause MASSIVE increase in prolactin
What steroids can be given in ACTH / cortisol replacement=
Hydrocortisone - current front line
Predisolone - potent steroid, longer half life, currently being trialled
How do you test acromegalY?
Oral glucose tolerance test (as glucose suppresses GH)
IGF-1 levels
How do you test GH deficiency in children?
Random plasma GH
Exercise then test GH (exercise causes GH release)
Do NOT do a GH stimulation test right away
After these you can try INSULIN TOLERANCE TEST
How do you treat acromegaly?
Octreotide (suppresses GH)
Cabergoline (if tumour is co-secreting prolactin)
Pituitary surgery
Pituitary radiotherapy
