Usually, it is symptomless and may not need treatment. T4 (thyroxine) is a major hormone secreted by your thyroid gland. T3 (triiodothyronine) is the active version of T4. The amount of T4 ...

Eun Lee, MD If your healthcare provider has ordered a T4 test, you may wonder what it is. Thyroxine is another name for T4, which is one of the two main types of thyroid hormone the thyroid gland ...