The normal value of total thyroxine is 45-109ng/ml, while free thyroxine is 11.5-22.7pmol/L. Normal values of thyroxine may vary slightly in different regions, hospitals, and using different testing methods, so it is recommended that patients compare the normal values of their local hospitals, or consult with a specialist. Thyroxine is tetraiodothyronine (T4), a hormone secreted by the thyroid gland, which is secreted into the bloodstream and partially bound to proteins, known as bound thyroxine, and exists in a free form, known as free thyroxine (FT4), with the sum of the two being total thyroxine (TT4). If abnormal thyroxine levels are present, prompt medical attention is recommended.