Endo - Pituitary tumours

Question 1

What are the classifications of a pituitary tumour?

Answer 1

Size:
- Microadenoma (<1cm)
- Macroadenoma (>1cm)
Sella or suprasellar - Has it grown out of the sella turcica
Compressing the optic chiasm or not?
Invading cavernous sinus or not?
Functional tumour - does it make too much hormone 
Benign or malignant?

Question 2

By what mechanism does excess prolactin cause problems?

Answer 2

1) Excess prolactin binds to kisspeptin neurons in the hypothalamus
2) This inhibits kisspeptin release
3) Decreases downsteam GnRH
4) Leads to oligo-amenorrhoea/low libido/infertility/osteoporosis/galactorrhoea

Question 3

What are other causes for an elevated prolactin level besides tumours?

Answer 3

Physiologocial:
- Pregnancy/breastfeeding
- Stress: exercise, seizure, venepuncture
- Nipple/chest wall stimulation
Pathological:
- Primary hypothyroidism
- Polycistic ovarian syndrome
- Chronic renal failure
Iatrogenic:
- Antipsychotics
- Selective serotonin re-uptake inhibitors
- Anti-emetics
- High dose oestrogen
- Opiates

Question 4

What can cause a false elevated serum prolactin level?

Answer 4

Macroprolactin:

• ‘Sticky prolactin’
• Polymeric form of prolactin
• Prolactin flows through body stuck together and gives a higher prolactin level reading

Stress of venepuncture:

• Stress of blood test can increase prolactin levels
• Exclude by a cannulated prolactin series

Question 5

What is the treatment of a prolactinoma?

Answer 5

No need for surgery:

• Give dopamine receptor agonist:
  
  • Cabergoline

Question 6

How do dopamine receptor agonists work?

Answer 6

• Dopamine usually binds to D2 receptors and prevents prolactin secretion
• Cabergoline can bind to D2 receptors and inhibit prolactin secretion

Question 7

What is the difference between gigantism and acromegaly?

Answer 7

Gigantism - chidren (growth plates on bones have not fused)

Acromegaly - adults (only soft tissue can grow)

Question 8

How do you detect and diagnose acromegaly?

Answer 8

• Measure IGF-1
  &
• Give them a high glucose drink
• Measure growth hormone: In normal GH should go down, in acromegaly, GH goes up

Question 9

What is the treatment for acromegaly?

Answer 9

• Surgery: Trans-sphenoidal pituitary surgery

- Give somatostatin analogue to shrink pituitary tumour before surgery