Molecular pathology of the pituitary. Development and functional differentiation of pituitary adenomas.

This review article describes functional differentiation of the pituitary cells and pituitary adenomas with special emphasis on transcription factors and co-factors. Human pituitary adenomas generally follow the combination of transcription factors and co-factors, which are similar to those of physiologic anterior pituitary cells. On very rare occasions, the single pituitary adenoma produces two hormones, which belong to different cell lineage 'trans-cell lineage'. Basic mechanism for this was considered to be 'aberrant expression' of transcription factors, i.e. NeuroD1 and Pit-1. This was experimentally supported by the induction of GH (mRNA and protein) in AtT-20 cells by transfecting Pit-1 gene. Various mechanisms have been reported for the experimental pituitary oncogenesis. Among these, GHRH has been emphasized as one of oncogenic factors for both human GHomas as well as in the transgenic animals.