CHEMPATH: Pituitary Flashcards
Does pituitary failure cause hypotension?
No - you still have aldosterone so you do NOT get hypotension.
What is the BP in Addison’s disease?
Low
What are the 6 hormones in the anterior pituitary?
- GHRH –> GH
- TRH –> TSH, prolactin
- Dopamine – > lowers prolactin
- LHRH/GnRH –> LH, FSH
- CRH –> ACTH
Why does primary hypothyroidism cause hyperprolactinaemia?
Because TRH stimulates its production
What is a macroadenoma?
pituitary tumour >1cm
What are some symptoms of pituitary failure e.g. due to macroadenoma?
- Galactorrhoea
- Amenorrhoea
- Bitemporal hemianopia
If the prolactin is >6,000, what is the diagnosis?
Prolactinoma is the only cause of such a high prolactin
NB: make sure that the patient is not pregnant
How do you test temporal vision?
Humphreys 30-2 test - if the blind spot is not black then this is a false negative and they must have looked at the light
What is shown below?
Development of bitemporal hemianopia in a pituitary adenoma
What is a normal prolactin level?
<600
What is the CPFT?
Combined pituitary function test - “triple test”
You give… to induce hypoglycaemic stress:
- GnRH/LHRH –> causes LH/FSH rise
- TRH –> causes TSH and prolactin release
- Insulin (hypoglycaeemic stress)
- increases CRF –> increased ACTH –> increased cortisol –> increased glucose
- increased GHRH –> increased GH –> increased glucose
What are the risks of CPFT and how is this managed? What is the target level for hypoglycaemia?
Can be dangerous due to risk of hypoglycaemia, so must have good IV acess so that you can give glucose if they become hypoglycaemic. Give 50mL of 20% glucose and patient will wake up in about 5 min.
However, you must ensure adequate hypoglycaemia <2.2mM
What is the method for the CPFT?
- Fast patient overnight
- Ensure good IV access
- Weight pt. and calculate dose of insulin required (0.15units/kg i.e. 70kg woman = 10.5units)
- Mix and IV. Inject the following (patient may vomit on injection):
- Insulin 0.15 units/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
Interpret these CPFT results.
Normal.
Interpret these CPFT results.
Pituitary macroadenoma (functioning) - abnormal, requires replacement of all hormones but hydrocortisone is urgent as you need this to respond to stress.
What is the management of the previous patient with abnormal CPFT?
- 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 – if prolactinoma is the cause of the failure –> shrinks tumour)
- Dopamine agonists
If the patient (female) only presents with bitemporal hemianopia, what is the diagnosis?
Non-functioning pituitary adenoma
What are the prolactin levels in non-functioning pituitary adenoma vs prolactinoma?
Prolactin is high (~2000) but lower than in prolactinoma.
Name 2 dopamine agonists.
- Bromocriptine (3 times a day)
- Carbegoline (once a week)
Interpret these CPFT results. What is the pathophysiology?
Disconnection hyperprolactinaemia (non-functioning pituitary adenoma).
- Adenoma presses on pituitary stalk
- Dopamine prevented from reaching anterior pituitary
- No -ve inhibition on prolactin release
- Hyperprolactinaemia
Do you need to use rescue therapy in CPFT in disconnection hyperprolactinaemia?
No because they rescue themselves with adrenaline
What is the management of non-functioning pituitary adenoma?
This still cuts off all the hypothalamic releasing 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
What type of prolactinaemia occurs in disconnection hyperprolactinaemia?
Secondary hyperprolactinaemia
This is also often caused by psychiatric drugs.
Which of these does a patient with disconnection hyperprolactinaemia not need and why?
- Fludrocortisone
- Hydrocortisone
- Thyroxine
- Oestrogen
- GH
Fludrocortisone - not a pituitary hormone, not affected in pituitary conditions.
Do you need to give carbegoline/bromocriptine in disconnection hyperprolactinaemia?
No treatment as this is non-functioning. However, in some it may be preferred…
Carbegoline is a dopamine agonist and it will not shrink the tumour - but this brings down the prolactin and allows women to ovulate and men to be fertile.
Should you use prednisolone or hydrocortisone for steroid replacement in pituitary failure?
- 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)
What is the diagnosis?
(Case presentation - 28yo, 2cm pituitary adenoma, bitemporal hemianopia, high persistent GH)
Acromegaly
What dynamic test is used for acromegaly? How is this done?
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
Apart from OGTT, what else can be used for acromegaly?
Serum IGF-1
What is the best treatment for acromegaly? What are the other treatment options?
- Pituitary surgery (the best treatment option)
- Pituitary radiotherapy
- Cabergoline
- Octreotide (somatostatin analogue; good at reducing the size of the tumour)
What is this?
Adrenals
