8: Pituitary Flashcards
Does pituitary failure cause hypotension?
Pituitary failure does NOT cause hypotension, it’s the loss of aldosterone that causes hypotension (if the pituitary gland fails, you can still produce aldosterone because the adrenal glands are intact)
Hypothalamic and anterior pituitary hormones
What are the signs of pituitary failure?
- Galactorrhoea
- Amenorrhoea
- Bitemporal hemianopia (if >1cm macroadenoma is the cause pressing on optic chiasm)
What is the cause of a very high prolactin? >6,000
- it must be a prolactinoma this is the only cause of such a high prolactin
Is high prolactin/prolactinoma a problem?
- This is normally not too much of a problem, but if it interferes with the production or axis of the other pituitary hormones, this can become a problem, so you need to test for the other hormones pituitary function testing
What is in an CPFT? “triple test”
What things should we ensure during a CPFT?
- Check glucose regularly
- Ensure an adequate hypoglycaemia (<2.2mM)
- If severe hypoglycaemia occurs (or unconsciousness), rescue patient with 50mL of 20% dextrose
How do we carry out a CPFT?
Fast patient overnight
Ensure good IV access
Weigh 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
Contraindications of inducing hypoglycaemia?
- Cardiac risk factors (ECG normal, no angina, etc.)
- History of epilepsy
Effects of hypoglycaemia (2)
- sympathetic activation occurs → aggression (if patient needs glucose, this may be difficult so IV access helps)
- 2) when very low (<1.5mM), neuroglycopaenia may occur (patient loses consciousness / becomes confused)
CPFT results
what is a normal response stress testing result?
How do we treat an abnormal response stress testing?
URGENT → hydrocortisone replacement (fludrocortisone is not necessary as adrenals should still be able to make aldosterone as it is independent of the HPA)
Total therapy (ordered):
- Hydrocortisone replacement
- Thyroxine replacement
- Oestrogen replacement
- GH replacement
- (Cabergoline or Bromocriptine (Dopamine agonists)) – if prolactinoma is the cause of the failure → shrinks tumour)
Bitemporal hemianopia aka non-functioning pituitary adenoma → how does this lead to hyperprolactinaemia
Prolactin is high (~2,800) but MUCH lower than in prolactinoma (>6,000)
- Adenoma presses on pituitary stalk
- Dopamine prevented from reaching anterior pituitary
- No -ve inhibition on prolactin release
- Hyperprolactinaemia
Bitemporal hemianopia aka non-functioning pituitary adenoma mx
- Hydrocortisone replacement
- Thyroxine replacement
- Oestrogen replacement
- GH replacement
- Cabergoline or Bromocriptine – brings down prolactin and allows women to ovulate and men to be fertile
Steroid replacement: prednisolone vs hydrocortisone
- Hydrocortisone is used as a steroid replacement in pituitary failure (BD or TDS)
- However, prednisolone is more potent with a longer half-life that is more resistant to degradation
- Prednisolone can be given OD and matches circadian rhythm better (will be used more in future)
Acromegaly testing
Acromegaly signs and sx
Causes of high prolactin
