Abstract： Objective The aim of this study was to explore expression of pituitary tumor transforming gene (PTTG) in estrogen-induced pituitary tumorigenesis in rats, to investigate its role in this process. Methods Forty female Wistar rats of 8 weeks old were used in our study. All animals were surgically ovariectomized before experi-ment. The female Wistar rats were induced with benzoic acid estradiol by peritoneal injection. Expression of PTTG mRNA levels in the pituitary glands were detected by semi-quantitative reverse transcription polymerase chain reac-tion ( RT-PCR). The data for PTTG mRNA levels were analyzed by the soft ware of SPSS 11.5 for windows.Results Significant increases in pituitary weight were noted three months after peritoneal injection of estradiol. The serum prolactin concentration also increased sharply in the rats of estrogenized groups. The histopathological exami-nation for pituitary tissues in experimental groups was also consistent with the diagnosis of pituitary adenoma. The expression level of PTTG mRNA in pituitary tumors was significantly higher than that of control groups. Conclusion It can be inferred from our study that chronic treatment with estradiol can result in pituitary adenoma in female Wist-ar rats. PTTG mRNA in the pituitary glands is regulated by estradiol with possible involvement in estradiol induced tumorigenesis in rats.