Thyroxine (T4) Hormone Test - Thyroxine (T4) Test

This test measures the concentration of total thyroxine (T4) hormone in the blood serum, the main hormone secreted by the thyroid gland. The measurement includes both free (biologically active) T4 and T4 bound to transport proteins (thyroxine-binding globulin, TBG, and albumin). Measuring total T4 is an essential part of a thyroid function panel, along with T3 and TSH, to assess the actual secretion of hormones from the gland itself.