The thyroid gland, located in the neck, is responsible for maintaining the energy levels in the body. It also controls the body’s reaction to other hormones. This gland produces a hormone known as the triiodothyronine or T3. Some of the T3 hormone binds itself to body protein while some of it remains unbound. The Triiodothyronine Total test measures both these types T3 in the blood. This test indicates any and all kinds of thyroid problems. Its primary use is to detect the condition of hyperthyroidism. It also helps the doctor in prescribing the treatment for other thyroid disorders. The test is also known as T4 or free thyroxine. Thyroxine-Free and a combination of triiodothyronine (T3) together produce thyroid gland. It is through T4 that the body control rate is measured. It is all regulated in a feedback system. The doctor may order the T4 test if the doctor sees the abnormal result on a TSH test or suspects of hyperthyroidism or hypothyroidism. If the patient shows increased high rates, anxiety, sudden weight loss or being the insomnia, tremors in the hands or have visual disturbances, he can be a suspect for hyperthyroidism, and the T4 test can be called in for. Whereas weight gains, dry skin, cold intolerance, fatigue, hair loss, irregularity in menstruation cycle of women, constipation can be symptoms of hypothyroidism.