Diagnostic Blood Test:

Free Triiodothyronine (FT3) (LC/MS)

Free Triiodothyronine or FT3 is the active thyroid hormone. Its job is to regulate metabolism, body temperature, and heart rate. Optimal levels of FT3 support healthy insulin sensitivity, muscle growth, fat loss, brain function, and mood. Measuring FT3 levels can help detect hyperthyroidism (an overactive thyroid) or hypothyroidism (an underactive thyroid).

Free Triiodothyronine (FT3) is a measure of unbound Triiodothyronine (T3) that is available to the body’s tissues.

Direct measurement of FT3 by equilibrium dialysis, high-pressure liquid chromatography, and tandem mass spectrometry provides enhanced accuracy over commonly used analog methods and is not affected by clinical conditions that impact protein binding capacity. Examples of clinical conditions in which the FT3 by the LC/MS method may be preferred include congenital absence of thyroxine-binding protein (TBG), pregnancy, administration of oral contraceptives or hormone therapy, administration of atypical antipsychotic medications, malignancy or other critical illnesses.