There are 2 thyroid hormones that are produced by thyroid gland as T3 triiodothyronine and T4 thyroxine. Thyroid gland uses idodine and secretes these thyroid hormones for body functions. Thyroid gland is a butetrfly shaped small gland located infront of your neck, below the Adam’s apple.
Free T3 is the active form of the thyroid hormones. T4 is converted to T3 in liver and tissues for body usage. Thyroid hormones regulates your metabolic rate, energy production, heart rate, carbohydrate metabolism and so many other systems in your body. There are 2 forms of T3 as free T3 and bound T3. A small precentage of T3 is found free and the other part of T3 is bound to proteins in body. Body uses free T3 (fT3) for metabolic regulation functions.
T3 level may be decreased by some causes , but free T3 blood test would not be enough for hypothroidism diagnosis alone. If your thyroid gland can’t produce enough thyroid hormones, first TSH ( thyroid stimulating hormone) and free T4 blood tests should be done for hypothyroidism diagnosis. T3 level may be decreased by insufficient production by thyroid gland, also some type of other diseases may reduce T3 level.
Low T3 causes
- Hashimoto’s thyroiditis
- Thyroidectomy ; thyroid gland removal surgery
- Hypothyroidism , under active thyroid gland
- İodine deficiency
- Some type of pituitary gland problems
- Hypothalamus deficiency
- Being ill; long time illnes that you need to be hospitalized