Growth factors in pituitary tumors.

Prolactin-secreting tumors are the most frequently occurring neoplasms in the human pituitary. Although the clinical syndrome associated with prolactinomas is well recognized the molecular and cellular mechanisms leading to cell transformation and development of these tumors remain elusive. In this paper we summarize recent evidence suggesting that both hypothalamic and intrapituitary defects can be involved in the development of prolactinomas. In particular alterations of the hypothalamo-pituitary dopaminergic transmission result in the dysregulation of the proliferative activity of lactotrope cells leading to tumor development. Similarly changes in the expression and activity of resident growth factors also play a role in pituitary tumorigenesis. In particular both overexpression of TGF alpha and loss of NGF production appear to be involved in the development and progression of prolactin-secreting tumors.