what is the funcTion of T3 T4
Answers
The thyroid hormones Thyroxine (T4) and Triiodothyronine (T3) are produced and secreted by the thyroid gland.
Each molecule of T4 and T3 is made up of a protein and iodine (in the form of iodide). T4 contains 4 molecules of iodide and T3 contains 3 molecules of iodide – hence the names T4 and T3.
thyroxine molecle showing iodine
This is what T4 (Thyroxine) looks like. It’s bound to 4 iodine molecules, while T3 is bound to 3.
Interestingly, thyroid hormones are the only compounds in the body that contain iodine. This is why dietary intake of iodine is important for thyroid health.
T4 is produced by the thyroid gland in much greater amounts than T3, around 90% more. This is because when T4 reaches organs and body tissue, it’s converted into T3.
So T4 is basically a stepping stone required for T3.
T3 is the active form of thyroid hormone in that it influences many body processes, in particular the regulation of metabolism (1, 2).
The thyroid produces a hormone called triiodothyronine, known as T3. It also produces a hormone called thyroxine, known as T4. Together, these hormones regulate your body’s temperature, metabolism, and heart rate.
Most of the T3 in your body binds to protein. The T3 that doesn’t bind to protein is called free T3 and circulates unbound in your blood. The most common kind of T3 test, known as the T3 total test, measures both kinds of T3 in your blood.
your doctor might also order a T4 test or a TSH test. TSH, or thyroid-stimulating hormone, is the hormone that stimulates your thyroid to produce T3 and T4.