Pituitary Tumours in Hypopituitarism	

Hypopituitarism is most commonly caused by the presence of a pituitary tumour (Fig. 2.2). The tumour is usually benign and most frequently arises from the anterior lobe. Pituitary carcinoma is very rare indeed, but in such cases metastases occur inside or outside the nervous system.  
Pituitary tumours range widely in size and may extend outside the pituitary fossa to compress surrounding structures.
Hypopituitarism can occur as a result of compression of secretory cells in the normal gland by a pituitary tumour. Large nonsecreting tumours may also cause hypopituitarism by compressing the pituitary stalk and interfering with the delivery of hypothalamic hormones to the anterior pituitary. If dopamine secretion is interfered with in this way, hyperprolactinaemia may ensue.