Free thyroxine index is considered to be a reliable indicator of thyroid status in the presence of abnormalities in plasma protein binding. The free thyroxine index has generally been replaced by Free Thyroxine in the assessment of thyroid function, but is occasionally useful when a free T4 result is suspected of being anomalous.
Reference ranges for the free thyroxine index:
How to calculate the free thyroxine index?
The free thyroxine index (FTI) is determined by the following calculation:
Low levels are caused by hypothyroidism. Low results may also occur in hospitalised patients with non-thyroidal illness.
High levels are caused by hyperthyroidism.
$79 per year
$6.60 per month billed annually
Use promocode
$79 per year
$250 single payment
$45 per month
Save time on interpreting lab results with the largest database of biomarkers online. In-depth research on any test at your fingertips, all stored and tracked in one place.
Learn More
At HealthMatters, we're committed to maintaining the security and confidentiality of your personal information. We've put industry-leading security standards in place to help protect against the loss, misuse, or alteration of the information under our control. We use procedural, physical, and electronic security methods designed to prevent unauthorized people from getting access to this information. Our internal code of conduct adds additional privacy protection. All data is backed up multiple times a day and encrypted using SSL certificates. See our Privacy Policy for more details.
5-Methyltetrahydrofolate, Adiponectin, Albumin/Creatinine Ratio, Random Urine, C-Peptide, Serum, Ceruloplasmin, Cyclic AMP, Plasma, Dihydrotestosterone (female), Dihydrotestosterone (male), Estimated Average Glucose (eAG), Free Androgen Index, Free testosterone, Free Testosterone, Direct (Female), Free Testosterone, Direct (Male), Free Thyroxine, Free Thyroxine Index, Fructosamine, Glucose, Glutamic Acid Decarboxylase, Hemoglobin A1c (HbA1c), Homocysteine, Insulin (Fasting), Insulin Antibody, Insulin-Like Growth Factor I (IGF-1), Iodine, Serum/Plasma, Parathyroid Hormone (PTH), Serum, Pregnenolone, Reverse T3, Serum, Sex Hormone-Binding Globulin (SHBG), T3, Free, T4, Free, T4, Total (Thyroxine), T7 Index, Testosterone, Testosterone (Female/Child), Testosterone, Serum (Female), Thyroglobulin, Thyroglobulin Antibodies, Thyroid Peroxidase Antibodies (Anti-TPO Ab), Thyroid Stim Immunoglobulin, Thyroid-Stimulating Hormone (TSH), Thyrotropin Receptor Ab, Serum, Thyroxine-binding globulin, TBG, Total T3, Tri iodothyronine (T3) Uptake, Triiodothyronine, Serum
