Free T3

Triiodothyronine, commonly known as T3, is a crucial thyroid hormone. While most T3 circulates bound to proteins, a small fraction remains unbound, termed Free T3 (FT3) or T3 libre. It is this unbound, metabolically active form of T3 that directly influences cellular function throughout the body. The thyroid gland primarily produces T4, which is then converted into the more potent T3, primarily in peripheral tissues. FT3 plays a significant role in regulating metabolism, energy levels, body temperature, and heart function, among other vital processes.