Total Triiodothyronine (T3) Test
1,100 Kshs | Home Collection Available
Synonyms
T3 Test, Total triiodothyronine
Purpose
The Total Triiodothyronine (T3) Test is a blood test that measures the total amount of T3 hormone, both free and protein-bound, in the bloodstream. T3 is one of the primary hormones produced by the thyroid gland and plays a key role in regulating metabolism, body temperature, heart rate, and growth.
This test is crucial for evaluating thyroid function, especially when a patient shows symptoms of hyperthyroidism (such as weight loss, rapid heartbeat, or nervousness) but has normal T4 and TSH levels. It helps detect T3 toxicosis, a condition where T3 is elevated while T4 remains normal.
Other tests commonly performed alongside include TSH, Free T3 and Free T4, Thyroid Antibody Tests, and Thyroid Ultrasound or Imaging. These combined tests provide a comprehensive evaluation of thyroid health and help guide diagnosis and treatment decisions.
Patient Preparation
The patient should avoid taking biotin supplements at least 72 to sample collection.
Samples
1ml with a minimum volume of 0.7ml of serum or plasma collected in a Gel-barrier, red-top, or green top tube (lithium heparin). Avoid using EDTA, oxalate, or citrate plasma. Transfer the separated serum to a plastic transport tube if a red-top tube is used. Store the sample at room temperature.
Reference Range
>10years:71-180ng/dL
Results Turnaround
Within 24 hours of receipt of samples.
Diseases / Diagnostic indicators
The Total T3 Test helps assess thyroid activity and can indicate whether the thyroid gland is overactive or underactive. Here are some possible outcomes of the test;
- Elevated T3 Levels:
May indicate hyperthyroidism or T3 toxicosis, where the thyroid produces excess T3. Symptoms may include weight loss, heat intolerance, rapid heartbeat, and anxiety. Elevated levels may also be seen in Graves’ disease or during pregnancy due to hormone-binding protein changes.
- Decreased T3 Levels:
Often seen in chronic non-thyroidal illnesses, also known as euthyroid sick syndrome, where thyroid function appears normal, but T3 levels drop due to illness. Low levels may also point to hypothyroidism, especially in later stages, where the thyroid fails to produce enough hormones.
- Normal T3 Levels:
Typically indicates proper thyroid function. However, in some cases of early or subclinical thyroid disease, T3 might remain normal while other thyroid hormone levels (like TSH or T4) shift. For more information on F3 testing, read this study.