T7

FT₄ may be estimated indirectly by calculating T₇, which is the product of T₄ x T₃U. This calculation is an attempt to correct for variations in thyroxine binding proteins. T₇ will usually be elevated in patients with hyperthyroidism and decreased with hypothyroidism. It may be low in patients with nonthyroid illness.

Direct measurement of free T₄ is recommended instead of T₇.

Reference range is 1.22 - 4.86 for males and 0.99 - 4.71 for females.

Specimen requirement is one SST tube of blood.