Fibrinogen

Fibrinogen is a glycoprotein produced by the liver that plays a dual role as both a key clotting factor and an acute-phase inflammatory marker. In hemostasis, fibrinogen is converted to fibrin by thrombin, forming the structural meshwork of blood clots. In inflammation, it rises as part of the acute-phase response, similar to CRP but with the added consequence of directly affecting blood viscosity and clotting tendency.

Elevated fibrinogen increases cardiovascular risk through multiple mechanisms: it increases blood viscosity (making blood 'thicker' and harder to pump), promotes platelet aggregation, enhances fibrin deposition in arterial plaques, and serves as a substrate for thrombus formation at sites of plaque rupture. These effects are independent of and additive to traditional risk factors like cholesterol and blood pressure.

Fibrinogen levels rise with age, smoking, obesity, chronic inflammation, and physical inactivity. Conversely, regular aerobic exercise, omega-3 fatty acids, and smoking cessation are all associated with lower fibrinogen levels. While not a direct treatment target, persistently elevated levels signal an unfavorable inflammatory and prothrombotic milieu that warrants attention.