Estrogen Receptor Beta mRNA Expression in Normal and Adenomatous Pituitaries

Estrogen (E2), acting via its nuclear receptors, has been implicated in tumor development and growth, particularly in the pathogenesis of breast cancer. E2 also modulates anterior pituitary hormone production and is a potent cell mitogen. Until recently, the actions of E2 were thought to be mediated by a single estrogen receptor (ER) isoform (ER), and currently little is known of the pathophysiological relevance of the ER isoform. The presence of ER mRNA has been demonstrated by RT-PCR in the normal human pituitary, although expression of ER mRNA in human pituitary tumors has not been described. We have used semiquantitative RT-PCR to determine the relative levels of expression of ER mRNA in normal human pituitaries, non-functioning pituitary adenomas and GH-secreting tumors. ER mRNA was detected in normal pituitaries and all pituitary tumors examined. The ratio of ER mRNA to -actin mRNA expression was significantly reduced in non-functioning pituitary tumors (NFTs; 0.92 ± 0.09; mean ± SE; n=23) compared with findings in normal pituitaries (1.56 ± 0.21; mean ± SE; n=5; p<0.05 Student's t-test). Studies of ER protein expression are required to determine the functional significance of reduced ER mRNA expression in NFTs.