The liver serves several metabolic functions within the body including protein synthesis and metabolism. The liver is responsible for an array of proteins. Endocrine proteins produced by the liver include angiotensinogen, thrombopoietin, and insulin-like growth factor I. In children, the liver is primarily responsible for heme synthesis. In adults, bone marrow supplants heme production. However, the adult liver is still responsible for approximately 20% of heme synthesis. The liver plays a crucial role in the production of nearly all plasma proteins (albumin, alpha-1-acid glycoprotein, majority of coagulation cascade, and fibrinolytic pathways). Notable exceptions include: gamma globulins, factor III, IV, VIII. Proteins produced by the liver: protein S, protein C, protein Z, plasminogen activator inhibitor, antithrombin III. Vitamin K dependent proteins synthesized by the liver include: Factors II, VII, IX, and X, protein S and C.
Defined by: Richard Murray, MD