fibrinogeenin

Fibrinogeenin (fibrinogen) is a soluble plasma glycoprotein produced by hepatocytes in the liver and essential for blood coagulation. In humans, fibrinogen is a hexamer composed of two identical sets of three polypeptide chains: Aα, Bβ, and γ. The three chains are encoded by the FGA, FGB, and FGG genes. The molecule has a molecular weight of about 340 kDa and circulates in plasma at normal concentrations of roughly 2 to 4 g/L.

During coagulation, thrombin cleaves fibrinopeptides A and B from fibrinogen, releasing soluble fibrin monomers that polymerize to form a fibrin network. Factor XIIIa cross-links the fibrin strands to stabilize the clot. Fibrinogeenin also acts as an acute-phase protein, with plasma concentrations rising in inflammation, infection, and tissue injury.

Biosynthesis and regulation: Hepatic production is influenced by cytokines, particularly interleukin-6. Normal plasma levels vary with population and assay, but generally fall within the 2–4 g/L range. Levels rise during pregnancy and inflammatory states and fall in liver disease, severe malnutrition, or disseminated intravascular coagulation.

Clinical significance: Heritable deficiencies include afibrinogenemia and hypofibrinogenemia, causing bleeding tendencies, while dysfibrinogenemia involves structurally abnormal fibrinogen. Elevated fibrinogen is associated with increased risk of thrombosis and cardiovascular disease and can reflect inflammatory or infectious states. In pregnancy, abnormal levels can have implications for maternal and fetal health.

Measurement and management: Fibrinogeenin activity is typically measured by the Clauss functional assay, and antigen assays assess total fibrinogen mass. Treatment for deficiency in bleeding patients may involve fibrinogen concentrates, cryoprecipitate, or, when appropriate, fresh frozen plasma, along with management of the underlying condition.