Crimean-Congo Hemorrhagic Fever (CCHF) may exhibit a mild clinical course or a severe profile like mortal bleeding. The pathogenesis of the illness and reason of bleeding are unclear. However, endothelial injury is a key factor in the pathogenesis of the illness. Transforming growth factor beta (TGF-beta) is one of the materials involved in repairing injured endothelium. This is a significant polypeptide released in pretty much all cells and important for the regulation of cellular events, epithelium formation, inflammation, blood coagulation, and collagen synthesis. This study aimed to determine the prognostic significance of serum TGF-beta 1 levels in CCHF patients. We examined 120 patients hospitalized with CCHF diagnosis and their serum TGF-beta 1 was investigated, retrospectively. Patients were put into two groups according to the existence of hemorrhage. Forty-four (36.7%) patients had hemorrhage. TGF-beta 1 levels in patients with bleeding were 5.2 +/- 1.8, and 7.1 +/- 2.2 for non-bleeding (P < 0.0001). When ROC analysis was performed in patients with CCHF alone in order to identify patients with bleeding, at a TGF-beta 1 cut-off point of 4.9, AUC was 0.762 (0.675-0.835), sensitivity 59.1%, specificity 85.5%, PPV 70.3%, and NPV 78.3%. We summarize that TGF-beta 1 level and endothelial dysfunction can be related. A decreased TGF-beta 1 level is a likely prognostic and diagnostic factor for bleeding in CCHF patients. Therefore, this marker should be considered in the treatment strategy for these patients. (C) 2016 Wiley Periodicals, Inc.