Download Free T4

Screening test: Thyroid Stimulating
Hormone (test code TSH)
Screening test: Free Thyroxine
(Free T4) (test code FT4)
Low TSH
Elevated Free T4
Increased TSH
Normal Free T4
Normal Free T4
Consider ordering Free
triiodothyronine (Free T3) (test code
FT3).
Decreased Free T4
Hypothyroidism
Most common cause in the US is
due to Autoimmune thyroiditis
(Hashimoto’s thyroiditis, chronic
thyroiditis).
Elevated Free T3
Hyperthryoidism
Most common cause in the US is due
to Grave’s disease.
Consider ordering Thyroid
Stimulating Antibodies (test code
TSI), if other lab or clinical findings
are not characteristic.
Subclinical hypothyroidism
Consider ordering Thyroid
Peroxidase Antibodies (test code
ATPO) for prognostic evaluation of
progression to hypothyroidism in
Autoimmune thyroiditis.