1652 – SELco^® FT3

Intended Purpose

The SELco^® FT3 is a quantitative immunoassay for the determination of free Triiodothyronine (FT3) in human serum. The SELco^® FT3 is intended as an aid in the diagnosis of thyroid diseases in conjunction with other clinical and laboratory findings. The immunoassay is designed for manual professional in vitro diagnostic use.

Diagnostic Relevance

The SELco® FT3 provides clinicians with a reliable method to measure free Triiodothyronine (FT3) in human serum, supporting the diagnosis of thyroid disorders alongside additional clinical and laboratory data.

Thyroid hormones, including thyroxine (T4) and triiodothyronine (T3), circulate in two forms: a major protein-bound fraction and a minor free fraction. Changes in total thyroid hormone levels often result from altered protein concentrations or changes in hormone synthesis. Clinicians focus on the free fraction because persistent changes in unbound T3 and T4 directly indicate thyroid dysfunction. Evaluating FT3 provides a clearer understanding of hormone activity than measuring total T3 alone.

T3 is the most biologically active thyroid hormone, with up to 80% generated through peripheral de-iodination of T4. Clinicians often associate increased FT3 levels with hyperthyroidism. In some cases, an isolated elevation of FT3 indicates T3-thyrotoxicosis. Therefore, physicians measure FT3 not only for initial diagnosis but also to monitor patients undergoing triiodothyronine therapy, ensuring appropriate therapeutic management and early detection of hormone imbalances.