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.
|
Disorder |
Total T4 |
T3 Uptake |
T7 |
|
Primary hypothyroid |
Decreased |
Decreased |
Decreased |
|
Secondary hypothyroid |
Decreased |
Decreased |
Decreased |
|
Hyperthyroid |
Increased |
Increased |
Increased |
|
T3 Toxicosis |
Normal |
Normal |
Normal |
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.
