What is Thyroxine Total (T4 Total)?
Thyroxine total, commonly abbreviated as T4 TOTAL, is one of the main thyroid hormones produced by the thyroid gland. Together with the thyroid hormone triiodothyronine (T3), it regulates the metabolism of the body and affects a variety of physiological processes, including metabolism, energy metabolism and body temperature.
Why is total T4 analyzed?
Total T4 is a measurement of the total amount of thyroxine circulating in the blood. It includes both the free form of T4 and that bound to transport proteins, such as thyroxine-binding globulin (TBG) and albumin. Measuring T4 total is important because it gives an overall indication of the thyroid gland's function and production of hormones.
When it comes to thyroid health and function, it is important to measure not only the levels of total T4 but also the free levels of T4. This is because it is the free form of T4 that is biologically active and can affect the body's tissues and cells. Changes in total T4 levels can indicate various thyroid-related conditions, such as hyperthyroidism (overactive thyroid) or hypothyroidism (underactive thyroid). It may also be related to other medical conditions, such as liver or kidney disease, or be a consequence of drug treatment.
When total T4 levels are outside the normal range, it may be a signal for the doctor to take further action, including ordering other thyroid tests, performing additional tests or investigations to determine the cause of the abnormality, and designing an appropriate treatment plan.