Chem path 8 - Pituitary Flashcards
Why do patients with primary hypothyroidism present with hyperprolactinaemia?
TRH stimulates prolactin release
dopamine antagonises prolactin release
What size is a pituitary micro and macroadenoma?
Micro <1cm
Macro >1cm
A prolactin level above ? is highly suggestive of prolactinoma?
> 6,000 (normal cut off is 600)
What is the best method to assess pituitary function?
Combined pituitary function test (CPFT) - “Triple test”
What 3 hormones does the CPFT use to test pituitary function?
Insulin (increases CRH and thus ACTH, increases GHRH and thus GH)
LHRH/gnrh (LH/FSH)
TRH (TSH + prolactin)
What are the contraindications to CPFT?
Cardiac risk factors
History of epilepsy
What level of hypoglycaemia should be achieved?
<2.2 mM
If severe hypoglycaemia or unconsciousness occurs during CPFT, what should you do?
Administer 50mL of 20% dextrose
Outline the CPFT method
1) Fast pt overnight
2) Good IV access
3) Weight pt and calculate dose of insulin required (0.15U/Kg)
4) Administer all the hormones IV
5) Measure: glucose, cortisol, GH, LH, FSH, TSH, prolactin and T4 at 0,30 and 60 mins
6) Also measure Glucose, cortisol and GH at 90 and 120 mins
What dose of each hormone in the CPFT is required?
Insulin 0.15U/Kg
TRH 200mcg
LHRH 100mcg
What would a normal response of cortisol and GH be?
Cortisol: >550nM reached
GH >10IU/L
What would the response be in someone with a large tunmour?
None of the hormones would increase
How would you immediately manage someone with large tumour?
Hydrocortisone
If a patient has a prolactinoma what other drugs would you give?
Dopamine agonists e.g. cabergoline and bromocriptine
What would differentiate a non-functioning pituitary adenoma?
The prolactin will be raised but much lower than a prolactinoma
Difference between prednisolone and hydrocortisone
Pred: more potent with a longer half-life that is more resistant to degradation, therefore only giving one tablet OD can resemble the body’s natural circadian rhythm well
How do you test for acromegaly?
OGTT (75G —> glucose in 2 hours) (gold standard)
IGF-1
What are the results of OGTT in pt with acromegaly?
Paradoxical rise in GH
What are the treatment options for acromegaly?
Pituitary surgery (best option)
Pituitary radiotherapy (any tumour left behind post op)
Cabergoline (1/3 of tumours co-secrete prolactin)
Octreotide (somatostatin analogue)
