Abnormal circulating thyroxine-binding globulin concentration Decreased circulating thyroxine-binding globulin concentration 2023-03-12T14:06:26Z HP:0012509 Reduced thyroxin-binding globulin Thyroxin-binding globulin (TBG) is known as serpin peptidase inhibitor, clade A (alpha-1 antiproteinase, antitrypsin), member 7 (SERPINA7), Entrez Gene ID 6906. Individuals with TBG deficiency are euthyroid. TBG is responsible for carrying the thyroid hormones thyroxine (T4) and 3,5,3'-triiodothyronine (T3) in the bloodstream. The concentration of thyroxine-binding globulin (TBG) in the blood circulation is below the lower limit of normal. Thyroxine-binding globulin low in blood