Pituitary

Question 1

1. Why doesn’t hypopituitarism cause low blood pressure?

Answer 1

The adrenals are still able to produce aldosterone

Question 2

2. Which hypothalamic hormones affect prolactin release?

Answer 2

Dopamine – negative
TRH – positive
NOTE: hypothyroidism causes hyperprolactinaemia

Question 3

3. How might pituitary failure present in women?

Answer 3

Amenorrhoea and galactorrhoea

Question 4

5. What is the main problem with prolactinomas?

Answer 4

It might reduce/stop the production of other pituitary hormones (e.g. ACTH, TSH, GH)
High prolactin in itself is not much of an issue

Question 5

6. What is the CPFT?

Answer 5

Combined Rapid Anterior Pituitary Evaluation Panel

Test for pituitary function

Question 6

7. Which three stimuli of pituitary hormone secretion are used in the CPFT?

Answer 6

Hypoglycaemia – increases CRF/ACTH and increases GHRH/GH
TRH – increases TSH and prolactin
LHRH – increases LH and FSH

Question 7

8. What safety precautions must you take before subjecting a patient to hypoglycaemia?

Answer 7

No cardiac risk factors (needs a normal ECG)
No history of epilepsy
Ensure good IV access

Question 8

9. Describe the manifestations of increasing hypoglycaemia?

Answer 8

Initially, activation of the sympathetic nervous system will result in sweating, tachycardia etc.
When the blood glucose reaches < 1.5 mM, neuroglycopaenia may occur (loss of consciousness and confusion)

Question 9

10. What blood glucose concentration is normally required to stimulate the pituitary gland?

Answer 9

< 2.2 mM

Question 10

11. How should a patient be rescued if they experience severe hypoglycaemia during this test?

Answer 10

50 mL 20% dextrose

Question 11

13. Outline the dosing of various drugs in the CPFT.

Answer 11

5 mL syringe
Insulin (0.15 U/kg)
TRH 200 µg
LHRH 100 µg
NOTE: the patient may experience a warm flush and vomit when the drug is administered

Question 12

14. What should be measured in the blood and how often?

Answer 12

every 30 mins for 60 mins
Glucose
Cortisol
GH

every 30 mins for 120 mins
LH and FSH
TSH
Prolactin

Question 13

18. What level of cortisol and GH is considered a normal response?

Answer 13

Cortisol > 550 nM

GH > 10 IU/L

Question 14

19. List the order of hormone replacement in someone with panhypopituitarism.

Answer 14

HYDROCORTISONE 
Thyroxine 
Oestrogen 
GH 
NOTE: fludrocortisone is not necessary because the adrenals can still produce aldosterone

Question 15

20. How should a patient with a prolactinoma be treated?

Answer 15

Dopamine agonists (e.g. cabergoline) 
This reduces the size of the tumour and can avoid surgery

Question 16

21. What is disconnection hyperprolactinaemia?

Answer 16

Compression of the pituitary stalk by a tumour cuts off the negative effect of dopamine on pituitary prolactin secretion
This results in hyperprolactinaemia

Question 17

22. Why do non-functioning adenomas need surgery?

Answer 17

They do NOT respond to dopamine agonists

Question 18

23. Why might prednisolone replace hydrocortisone as the first-line steroid replacement agent?

Answer 18

It has a longer half-life meaning that once daily dosing is possible

Question 19

24. How should you investigate a child with poor growth who is suspected of having a GH deficiency?

Answer 19

Take a random plasma GH measurement (GH is pulsatile but if you happen to measure it during a pulse and they have detectable GH then it shows that they are producing GH)
Exercise test
Insulin tolerance test (effective but dangerous so should NOT be done straight away)

Question 20

25. Name two tests that may be used to investigate suspected acromegaly.

Answer 20

Oral glucose tolerance test

IGF-1 levels