The function of the thyroid gland is to take iodine, found in many foods, and convert it into thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Thyroid cells are the only cells in the body which can absorb iodine. These cells combine iodine and the amino acid tyrosine to make T3 and T4.
Doctor may order a T4 test if a thyroid-stimulating hormone (TSH) test has come back with abnormal results. A T4 test will help your doctor determine what type of problem is affecting your thyroid.
Normal range of Free T4 Test is 6-12 ug/d.
