The thyroid T4 hormone is also known as Thyroxine and is a hormone made by the thyroid gland. It performs many important duties including creating and increasing some of the substances that will later make energy for one’s body and interacting with other hormones to carry out basic but important thyroid function. T4 is usually attached to a protein, but when it is not, it is said to be free T4, so this is what a doctor is testing when he or she measures one’s free T4 thyroid levels. It is important to understand that though very similar T4 and free T4 thyroid levels are not the same thing and carry out different functions. Often, these functions may be related, but maintaining appropriate levels of both types of this hormone are important. In some cases, free T4 alone may be tested and vice versa. The type of test needed is almost always dependent only on the individual situation.
The normal range for this hormone is between 4.5 micrograms per deciliter, abbreviated mcg/dL and 11.2 mcg/dL. That is a general normal range, as sometimes there is a slight difference in what other laboratories consider average. It is importat that one’s doctor let his or her patient know what the results reveal. High levels may indicate a health problem. Tsh T4 tests also offer valuable information about one’s health. If the results of a Tsh T4 test reveal an overabundance of T4 and a deficiency of Tsh, then many health concerns are brought up. Conditions this could indicate include undiagnosed Hashimoto’s disease, Grave’s disease, certain types of tumors or growths, too high protein levels, hyperthyroidism, Trophoblastic disease, and many other serious conditions. It is important to note that the results of a hormone level test are not a diagnosis in themselves. They may indicate a problem, but they cannot tell which problem or issue one has, and ocassionally, the tests give false results. In this case, a retest or a different type of test may be necessary.
Low T4 levels could indicate malnutrition or the use of certain medications. As always, it is vital that one inform his or her doctor of any and all medications one is taking, planning to take, or may need to take in an emergency situation. Medications that may increase T4 levels include birth control pills, estrogen, methadone, and clofibrate. Medications that may decrease T4 levels include anabolic steroids, androgens, lithium, anti-depressants, propranolol, and any antithyroid drugs. Other drugs and medicines may also cause high, low, or otherwise abnormal readings. One should be sure to understand what his or her reading means and the appropriate measures he or she should follow to fix the problem if there is one. If one has further questions or points he or she does not understand, one should feel free to ask his or her doctor for more in-depth information on the thyroid T4 hormone, though these are the basics.