Chemical Pathology 20 - Pituitary Flashcards
(19 cards)
What hormones does the ant pituitary secrete?
Does pituitary failure cause hypotension?
No -
Hypotension is due to loss of aldosterone
In pit failure, aldosterone can still be produced as adrenals are intact
S/S of pituitary failure
galactorrhoea
amenorrhoea
bitemporal hemianopia (>1cm macroadenoma pressing on optic chiasm
Investigations of pituitary failure
Visual field assessment - Humphreys 30-2
MRI
Define prolactinoma
prolactin >6000
Investigations for prolactinoma
can interfere with prod of other pit hormones -> CPFT
What does the CPFT consist of?
Insulin (hypoglycaemic stress)
↑CRF → ↑ACTH → ↑cortisol → ↑glucose
↑GHRH → ↑GH → ↑glucose
adequate hypoglycaemia <2.2mM - need to check glucose regularly
TRH
↑TRH → ↑TSH + prolactin
GnRH/LHRH
↑LH/FH
Method for CPFT
- Fast patient overnight
- Ensure good IV access
- Weight pt. and calculate dose of insulin required (0.15U/kg → i.e. 70kg woman = 10.5U)
- Mix and IV. Inject the following (patient may vomit on injection):
- Insulin 0.15U/kg
- TRH 200mcg
- LHRH/GnRH 100mcg
- Take bloods at 0, 30 and 60 minutes of glucose, cortisol, GH, LH, FSH, TSH, prolactin and T4
- Take bloods at 90 and 120 minutes of glucose, cortisol and GH
- Treat any hypoglycaemia with 50mL 20% dextrose
Contraindications to CPFT
cardiac RFs: ECG normal, no angina
Hx of epilepsy
low glucose → SNS activation (aggression) → v low (<1.5mM) → neuroglycopenia (loose consciousness/confusion)
Normal response to CPFT
glucose <2.2mM
cortisol >450nM
GH > 10IU/L
glucose drop → ↑ TRH stressor → stimulated prolactin
Treatment for prolactinoma
HTOG
- Hydrocortisone replacement (URGENT)
- Thyroxine replacement
- Oestrogen replacement
- GH replacement
- Dopamine agonists (Cabergoline or Bromocriptine – if prolactinoma cause → shrinks tumour)
Is fludrocortisone necessary in prolactinoma?
No as adrenals should still be able to make aldosterone as it is independent of the HPA
What is a non-functioning adenoma
high prolactin (~2800) but <6000
adenoma presses on pituitary stalk → dopamine does not reach ant pituitary → no -ve inhibition on prolactin release → hyperprolactinaemia
Treatment for non functioning adenoma
still cuts of hypothalamic release hormones:
- Hydrocortisone replacement
- Thyroxine replacement
- Oestrogen replacement
- GH replacement
- Cabergoline or Bromocriptine – brings down prolactin and allows women to ovulate and men to be fertile
Acromegaly definition
high persistent GH
Acromegaly investigations
IGF-1 (produced by liver in response to GH → tissue and bone growth)
OGTT (75g of glucose → measure glucose in 2 hours)
- GH should drop with glucose
- In acromegaly, you get a paradoxical rise in GH with glucose administration
Management of acromegaly
Pituitary surgery (best treatment option)
Pituitary radiotherapy
Cabergoline
Octreotide (somatostatin analogue; good at reducing size of tumour)
