Thyroxine (T4) is a hormone synthesized and secreted by the thyroid gland. In circulation 99.95 % of T4 is reversibly bound to transport protein, primarily Thyroxine binding Globulin (TBG) and to a lesser extent albumin and thyroxin binding pre albumin (TBPA). The remaining T4 is not bound to transport proteins but it is free in the circula...
0.7 -1.8 ng/dl
When to get Tested
When there is s/s of Hyperthyroidism (Increased heart rate, Anxiety, weight loss, difficulty sleeping, tremors in the hands, weakness, and menstrual irregularity)