OBJECTIVES: In sporadic pituitary adenomas, the role of Ubiquitin-specific protease 8 (USP8) is not clearly defined. Mutations in USP8 gene are known to influence formation of the corticotroph adenomas. However, it has not been clarified whether changes in expression of USP8 have an impact on other pituitary adenomas or not. In this study we addressed the changes in USP8 gene expression levels in pituitary adenomas (PA) relative to non-adenomatous brain tissue. MATERIAL AND METHODS: USP8 gene expression analysis was performed on a total of 43 tissue samples from human pituitary adenomas and on 16 tissue samples from non-pituitary brain tissues (control group). Adenomatous tissues and control tissues were assessed for quantification of RNA expression of USP8.The levels of USP8 gene expression were determined relative to those in control group. RESULTS: Overall, the USP8 gene expression levels in PA were 3.7 times higher than the control brain tissues (CBT) (p=0.002). However, after stratification, only the USP8 in the secretory PA were higher than CBT(p=0.002). CONCLUSIONS: Present findings support that USP8 gene expression levels may contribute to pitutary tumorigenesis and hormonogenesis..