Introduction:Obsessive-Compulsive Disorder (OCD) as one of the important mental problems is valuable topic for proteomic research studies to better understand the underlying mechanisms of this disorder.Methods:In this paper, gel-based proteomic was used to investigate the proteome profile of 16 female patients with OCD, washing subtype before and after treatment with fluoxetine and comparing them with 20 healthy female controls.Results:One of the abnormally expressed protein spots in this study was introduced and examined for protein-protein interaction network analysis via Cytoscape and its plug-ins. Transthyretin (TTR) protein showed significant expression changes (fold change=1.7, P<0.05). While the expression level of TTR is significantly decreased in OCD patients before any treatments, the trend is partially normalized after treatment with fluoxetine in positive responders. Furthermore, TTR interaction profile shows that the proteins interacting with this protein may get affected as this protein expression trend changes in OCD patients.Conclusion:TTR can be considered for further studies to be validated as a potential biomarker for OCD.