Saturday, 11 September 2010

MRCP revision battle 8.5: Pituitary tumours

Most pituitary tumours are benign adenomas.

Symptoms from pituitary tumours are either due to:
  • local pressure
  • hormone secretion
  • hypopituitism

Local pressure symptoms include:
  • bitemporal hemianopia (pressure on CN III)
  • palsies of CN III/IV/VI (remember the cavernous sinus anatomy at the end of battle 1.1?)

The commonest hormone secreted by pituitary tumours is prolactin (35%) followed by GH (20%).

30% of pituitary tumours secrete no obvious hormone

Potentially a pituitary tumour can disturb hypothalamic control of temperature, sleep or appetite.

If the tumour erodes the floor of the sella the patient may get CSF rhinorrhoea

Histologically, pituitary tumours fall into the following catagories:
  • 70% - chromophobes
    • 30% cause a pressure effect
    • can produce prolactin, ACTH, GH
  • 15% - acidophils
    • 10% cause a pressure effect
    • can produce GH, prolactin
  • 15%  - basophils
    • rarely cause a pressure effect
    • can produce ACTH

The investigation of choice for suspected pituitary tumours  is MRI.

Finally, in this section we need to cover Nelsons Syndrome.  Nelsons syndrome is a condition that occurs after adrenalectomy for pituitary-dependent cushings.  The adrenalectomy removes the negative feedback on the pituitary which causes ACTH levels to rise massively, leading to hyperpigmentation +/- an invasive pituitary tumour.

Tomorrow we will look at craniopharyngioma, but to finish today on a lighter note onwards to Romano Ward and Jervell-Lange-Nielson Syndromes.