Fibrinogen
Fibrinogen (coagulation factor I) is a glycoprotein complex, produced in the liver,[1] that circulates in the blood of all vertebrates.[2] During tissue and vascular injury, it is converted enzymatically by thrombin to fibrin and then to a fibrin-based blood clot. Fibrin clots function primarily to occlude blood vessels to stop bleeding. Fibrin also binds and reduces the activity of thrombin. This activity, sometimes referred to as antithrombin I, limits clotting.[1] Fibrin also mediates blood platelet and endothelial cell spreading, tissue fibroblast proliferation, capillary tube formation, and angiogenesis and thereby promotes revascularization and wound healing.[3]
Fibrinogen alpha/beta chain family
Fib_alpha
Fibrinogen_aC
Fibrinogen_C
Reduced and/or dysfunctional fibrinogens occur in various congenital and acquired human fibrinogen-related disorders. These disorders represent a group of rare conditions in which individuals may present with severe episodes of pathological bleeding and thrombosis; these conditions are treated by supplementing blood fibrinogen levels and inhibiting blood clotting, respectively.[4][5] These disorders may also be the cause of certain liver and kidney diseases.[1]
Fibrinogen is a "positive" acute-phase protein, i.e. its blood levels rise in response to systemic inflammation, tissue injury, and certain other events. It is also elevated in various cancers. Elevated levels of fibrinogen in inflammation as well as cancer and other conditions have been suggested to be the cause of thrombosis and vascular injury that accompanies these conditions.[6][7]
Clinical analyses of the fibrinogen disorders typically measure blood clotting using the following successive steps:[28] Higher levels are, amongst others, associated with cardiovascular disease (>3.43 g/L). It may be elevated in any form of inflammation, as it is an acute-phase protein; for example, it is especially apparent in human gingival tissue during the initial phase of periodontal disease.[29][30]
Hyperfibrinogenemia[edit]
Levels of functionally normal fibrinogen increase in pregnancy to an average of 4.5 gram/liter (g/L) compared to an average of 3 g/L in non-pregnant people. They may also increase in various forms of cancer, particularly gastric, lung, prostate, and ovarian cancers. In these cases, the hyperfibrinogenemia may contribute to the development of pathological thrombosis. A particular pattern of migratory superficial vein thrombosis, termed trousseau's syndrome, occurs in, and may precede all other signs and symptoms of, these cancers.[7][32] Hyperfibrinogenemia has also been linked as a cause of persistent pulmonary hypertension of the newborn[33] and post-operative thrombosis.[34] High fibrinogen levels had been proposed as a predictor of hemorrhagic complications during catheter-directed thrombolysis for acute or subacute peripheral native artery and arterial bypass occlusions.[35] However, a systematic review of the available literature until January 2016 found that the predictive value of plasma fibrinogen level for predicting hemorrhagic complications after catheter-directed thrombolysis is unproven.[36]
History[edit]
Paul Morawitz in 1905 described fibrinogen.[37]