The pathogenesis of sporadic pituitary tumours remains elusive. Recently, a new candidate gene has been described which is able to induce pituitary cell transformation, and the expression of which appears to be strongly correlated with pituitary tumorigenesis. The so-called pituitary tumour transforming gene (PTTG) encodes a 23 kDa, 202 amino acid protein, and is located on chromosome 5q33, a locus previously associated with recurrent lung cancer and acute myelogenous leukaemias. Although the precise function of PTTG protein is unknown, in vitro experiments have demonstrated that it is capable of inducing fibroblast growth factor (FGF) expression. Mutation of the two proline-rich domains of the PTTG protein has also been shown to abolish subsequent FGF induction. Furthermore, in patients with pituitary adenomas, serum FGF concentrations fall post-operatively after successful excision of the tumour.