Almost all tumours of the pituitary gland are benign and do not spread. They are sometimes called adenomas. Pituitary tumours are either secreting(producing hormones) or non-secreting tumours(not producing hormones).Secreting tumours can release excess amounts of any of the pituitary hormones and are named after the hormone that is being over-produced, eg, a prolactin-secreting tumour.
Attribution: BUPA