Triiodothyronine Free (FT3)


Triiodothyronine Free (FT3) is a blood test that measures the free or unbound (bioavailable) Free T3 hormone available to receptor sites. Free T3 is the most active form of the thyroid hormone and is primarily produced from the conversion of thyroxine in the peripheral tissue.

Approximately 20% of thyroxine (T4) is converted to triiodothyronine (T3) in the intestines, but only in the presence of friendly flora such as Lactobacillus acidophilus and Bifidobacteria. Triiodothyronine Free (FT3) is used to measure Free T3, the active form of thyroid hormone. It is an excellent marker to measure the amount of active thyroid hormone that is available to bind with thyroid receptor sites. Many health care providers believe that evaluating (FT3) is the best indicator of thyroid function. A (FT3) test is frequently used to support a diagnosis of hypothyroidism or hyperthyroidism. Hypothyroidism is a condition where (FT3) blood levels are low. Symptoms may include weight gain, constipation, dry skin and hair loss. When low (FT3) levels go undetected, chronic diseases such as heart disease and diabetes may develop. Hyperthyroidism is the term for elevated T3 blood levels. Symptoms can include anxiety, insomnia, heart palpitations and bowel discomfort.  Many factors may disrupt the balance of thyroid hormone production, including medications, allergies (wheat & gluten), anemia, poor gastrointestinal function, insulin resistance, bone metabolism, hormone imbalances, nutrient deficiencies such as selenium, decreased levels of Vitamin A & D and metabolic disruptors such as PCBs to name a few.

Test Preparation For Optimal Results:

If possible, have the lab collected early in the morning or shortly after waking. For comparison purposes, have subsequent labs collected close to the same time.

Disclaimer: Your health care provider should evaluate a deviation from normal ranges.