Thyroxine Free T4 Low. A low tsh and low ft4 or fti indicates hypothyroidism due to a problem involving the pituitary gland. The normal level of free thyroxine in the body of an adult is 0.8 to 2.8 nanograms per deciliter (ng/dl).
This means your thyroid is not making enough hormones. Normal t4 levels also vary across trimesters of pregnancy. A high t4 result could mean you have hyperthyroidism.
Your hypothalamus and pituitary glands control the release of t4.
If your t4 test results are not normal, your health care provider will likely order more thyroid tests to help make a diagnosis. The term “free thyroxine” means measured thyroxine that is not bound to proteins in the blood. A high level of tsh and a low level of t4 in the blood could mean you have an underactive thyroid. We have studied 18 patients with low serum thyrotrophin (tsh) levels accompanied by normal thyroxine (t4) and triiodothyronine (t3) levels in order to clarify whether or not they are thyrotoxic.
