Antithrombin is a small molecule that inactivates several enzymes of the coagulation system. It is a glycoprotein produced by the liver.

Function

---

Antithrombin is a serpin (serine protease inhibitor) that inactivates a number of enzymes from the coagulation system, namely the activated forms of Factor X, Factor IX, Factor II (thrombin), Factor VII, Factor XI, and Factor XII. Its affinity for these molecules (i.e. its effectivity) is enhanced by heparin.

Role in disease

---

Antithrombin deficiency is a rare hereditary disorder that generally comes to light when a patient suffers recurrent venous thrombosis and pulmonary embolism. This was first described by Egeberg in 1965. The patients are treated with anticoagulants or, more rarely, with antithrombin concentrate.

In renal failure, especially nephrotic syndrome, antithrombin is lost in the urine, leading to a higher activity of Factor II and Factor X and in increased tendency to thrombosis.

Genetics

---

The gene for antithrombin is located on the first chromosome, locus 1q23-q25.1.

Nomenclature

---

Antithrombin is officially called antithrombin III and is a member of a larger family of antithrombins (numbered I, II etc. to VI). All are serpins. Only AT III (and possibly AT I) is medically significant, with AT III generally referred to as antithrombin.

Reference

---

• Egeberg O. Inherited antithrombin deficiency causing thrombophilia. Thromb Diath Haemorrh 1965;13:516–520. PMID 14347873.

External links

---

• Patient's pages on antithrombin
• (antithrombin deficiency)

Coagulation system | Serine protease inhibitors

Antithrombin | Antitrombina | Antitrombina