Proteins produced and secreted by the liver explained

The liver plays the major role in producing proteins that are secreted into the blood, including major plasma proteins, factors in hemostasis and fibrinolysis, carrier proteins, hormones, prohormones and apolipoprotein:

Major plasma proteins

All plasma proteins except Gamma-globulins are synthesised in the liver.^[1]

• Human serum albumin, osmolyte and carrier protein
• α-fetoprotein, the fetal counterpart of serum albumin
• Soluble plasma fibronectin, forming a blood clot that stops bleeding
• C-reactive protein, opsonin on microbes,^[2] acute phase protein
• Various other globulins

Factors in hemostasis and fibrinolysis

• Stimulators of coagulation:
  • All factors in the coagulation cascade.^[3]
  • While the endothelium does produce some factor VIII, the majority of factor VIII is produced in the liver.^[4]
• Inhibitors of coagulation: Inactivate an enormous variety of proteinases
  • α2-macroglobulin
  • α1-antitrypsin
  • Antithrombin III
  • Protein S
  • Protein C
• Fibrinolysis: Breakdown of fibrin clots
  • Plasminogen
• Inhibitors of fibrinolysis
  • α2-antiplasmin
• Complement components C1-9, complement component 3 (C3)

Carrier proteins

• Albumin, carries thyroid hormones and other hormones, particularly fat soluble ones, fatty acids to the liver, unconjugated bilirubin, many drugs and Ca²⁺
• Ceruloplasmin, carries copper
• Transcortin, carries cortisol, aldosterone and progesterone
• Haptoglobin, carries free hemoglobin released from erythrocytes
• Hemopexin, carries free heme released from hemoglobin
• IGF binding protein, carries insulin-like growth factor 1
• Major urinary proteins, carries pheromones in rodents
• Retinol binding protein, carries retinol
• Sex hormone-binding globulin, carries sex hormones, specifically testosterone and estradiol
• Thyroxine-binding globulin, carries the thyroid hormones thyroxine (T4) and 3,5,3’-triiodothyronine (T3)
• Transthyretin, carries the thyroid hormone thyroxine (T4)
• Transferrin, carries iron ions in the ferric form (Fe³⁺)
• Vitamin D-binding protein, carries vitamin D

Hormones

• FGF21, a protein hormone that induces mitochondrial oxidation of fatty acids, hepatic gluconeogenesis, and ketogenesis in response to fasting.
• Hepcidin, a peptide hormone that regulates iron homeostasis.
• Insulin-like growth factor 1, a polypeptide protein hormone which plays an important role in childhood growth and continues to have anabolic effects in adults
• Thrombopoietin, a glycoprotein hormone that regulates the production of platelets by the bone marrow

Prohormones

• Angiotensinogen, when converted to angiotensin causes vasoconstriction and release of aldosterone, in effect increasing blood pressure

Apolipoproteins

• Almost all apolipoprotein, except apo B48 (produced by intestine)

References

General reference for the list of included substances (but not their functions):

• Table 45–4 in: Book: Walter F., PhD. Boron . Medical Physiology: A Cellular And Molecular Approaoch . Elsevier/Saunders . 2003 . 1300 . 1-4160-2328-3 .

Other:

Notes and References

1. Miller. L. L.. Bale. W. F.. February 1954. Synthesis of all plasma protein fractions except gamma globulins by the liver; the use of zone electrophoresis and lysine-epsilon-C14 to define the plasma proteins synthesized by the isolated perfused liver. The Journal of Experimental Medicine. 99. 2. 125–132. 10.1084/jem.99.2.125. 0022-1007. 2180344. 13130789.
2. Lippincott's Illustrated Reviews: Immunology. Paperback: 384 pages. Publisher: Lippincott Williams & Wilkins; (July 1, 2007). Language: English. . Page 182
3. BRS Pathology 5th Edition, pg. 196
4. Robbins Basic Pathology 9th Edition, Chapter 11