Thyroxine Blood Test (T4)

Thyroxine (T4) is the major secretory hormone of the thyroid. Only 0.03% of T4 is unbound and free for exchange with tissues. Thyroid function may be assessed with thyroid stimulating hormone (TSH) and free T4 measurements.

Thyroxine (T4) is the major secretory hormone of the thyroid. Only 0.03% of T4 is unbound and free for exchange with tissues. Thyroid function may be assessed with thyroid stimulating hormone (TSH) and free T4 measurements.