The fT3 Rapid Quantitative Test is a fluorescence immunoassay designed for the precise measurement of free triiodothyronine (fT3) levels in human serum. Triiodothyronine (T3) and thyroxine (T4), secreted by the thyroid gland, play a critical role in regulating metabolism, cardiovascular health, growth, bone development, and the function of the nervous and reproductive systems.

In circulation, T3 exists as both free and protein-bound hormone, with free T3 (fT3) representing only 0.2–0.4% of total T3 yet serving as the biologically active form. Measuring free T3 is vital, as it provides an accurate assessment of thyroid function independent of fluctuations in thyroid hormone-binding proteins.

This test supports clinical differentiation of thyroid disorders, particularly useful in identifying various forms of hyperthyroidism and T3 thyrotoxicosis. With its rapid, simple, and accurate testing process, the fT3 Rapid Quantitative Test is ideal for use in hospitals, clinics, and endocrinology centers.