From the Research
Elevated Antithrombin III (AT-III) activity is primarily caused by acute phase reactions during inflammation, exogenous administration of AT-III concentrates, and certain medications. The causes of elevated Antithrombin III activity can be broken down into several key categories, including:
- Acute phase reactions during inflammation, where the liver increases production of AT-III as part of the body's defense mechanism 1
- Exogenous administration of AT-III concentrates for therapeutic purposes, such as in patients with hereditary AT-III deficiency or disseminated intravascular coagulation (DIC) 2
- Certain medications, including anabolic steroids like stanozolol and danazol, which stimulate hepatic synthesis of AT-III, as well as oral contraceptives containing estrogen 1 Additionally, heparin therapy can cause apparent increases in AT-III activity in laboratory tests due to its mechanism of enhancing AT-III function, though this represents increased functional activity rather than concentration 3. It's also worth noting that pregnancy, especially in the second and third trimesters, can lead to physiologically elevated AT-III levels 1. However, elevated AT-III activity is rarely a clinical concern as it generally doesn't increase thrombotic risk, unlike deficiencies which significantly increase clotting risk 4. In terms of specific patient populations, a study from 2018 found that rivaroxaban may be an effective and safe treatment option for venous thromboembolism in patients with nephrotic syndrome and low AT-III levels 3. Overall, the causes of elevated AT-III activity are multifaceted and can be influenced by a range of factors, including inflammation, medication use, and underlying medical conditions.