T4 normal range

Clinical Information The determination of the total thyroxine (T4) concentration is of importance in laboratory diagnostics for differentiating between euthyroid, hyperthyroid, and hypothyroid conditions. As the major fraction of the total T4 is bound to transport proteins (thyroxine-binding globulin [TBG], prealbumin, and albumin), the determination of total T4 only provides correct information when the thyroxine-binding capacity (TBC) in serum is normal. The free thyroid hormones are in equilibrium with the hormones bound to the carrier proteins. The TBC or T-uptake assay provides a measure of the available thyroxine-binding sites. Determination of the free thyroxine index (FTI) from the quotient of total T4 and thyroxine-binding index (ie, result of the T-uptake determination) takes into account changes in the thyroid hormone carrier proteins and the thyroxine level. While total T4 is a relatively reliable indicator of T4 levels in the presence of normal binding proteins, it is not a reliable indicator when binding proteins are abnormal. For example, increases in thyroxine-binding proteins may cause increased total T4 levels despite normal free T4 levels and normal thyroid function. Results are changed by drugs or physical conditions that alter the patient's TBG levels or drugs that compete with endogenous T4 and T3 for protein-binding sites. Direct measurement of free thyroxine (FRT4 / T4 [Thyroxine], Free, Serum) has replaced the FTI test in most clinical situations. ...

Your health care provider will tell you if you need to stop taking any medicines that may affect the test result. In general, test results are not affected by other medicines you may be taking. However, certain supplements including biotin (vitamin B7) can affect the results. Tell your provider if you are taking biotin. Pregnancy and some diseases, including kidney and liver disease, can also affect the results of this test. Your provider may recommend this test if you have signs of a thyroid disorder, including: • Abnormal findings of other thyroid blood tests, such as • Symptoms of an • Symptoms of an • Hypopituitarism -- when the pituitary gland does not produce enough of its hormones, including the hormone which stimulates the thyroid • • Enlarged or irregular thyroid gland • Problems becoming pregnant This test is also used to monitor people who are being treated for thyroid problems. A typical normal range is 0.9 to 2.3 nanograms per deciliter (ng/dL), or 12 to 30 picomoles per liter (pmol/L). Normal value ranges may vary slightly among different laboratories. Some laboratories use different measurements or may test different specimens. Talk to your provider about the meaning of your specific test results. The normal range is based on a large population and is not necessarily normal for an individual. You may be having symptoms of hyperthyroidism or hypothyroidism even though your free T4 is in the normal range. The TSH test may help determine if your symptoms are re...

Subclinical hyperthyroidism is when thyroid-stimulating hormone (TSH) levels are low or undetectable, but thyroid hormone levels remain healthy. Usually, it is symptomless and may not need treatment. Subclinical hyperthyroidism is when you have low T4 (thyroxine) is a major hormone secreted by your Therefore, if your pituitary gland sees very little T4, it will produce more TSH to tell your thyroid gland to produce more T4. Once the amount of T4 reaches appropriate levels, your pituitary gland recognizes that and stops producing TSH. In people with subclinical hyperthyroidism, the thyroid produces normal levels of T4 and T3. Yet, they have lower-than-normal TSH levels. This imbalance of hormones leads to the condition. The prevalence of subclinical hyperthyroidism in the general population is estimated to range from Subclinical hyperthyroidism can be caused by both internal (endogenous) and external (exogenous) factors. Internal causes of subclinical hyperthyroidism can include: • Graves’ disease. • Multinodular goiter. An enlarged thyroid gland is called a goiter. A • Thyroiditis. • Thyroid adenoma. A thyroid adenoma is a External causes of subclinical hyperthyroidism include: • excessive TSH-suppressive therapy • unintentional TSH suppression during hormone therapy for Subclinical hyperthyroidism can occur in pregnant women, particularly in the first trimester. However, it’s If your doctor suspects that you have subclinical hyperthyroidism, they’ll first assess your If y...