TSH, T4, T3 test explained

If you have had thyroid test results come back showing you have high levels of thyroid stimulating hormones (TSH) then this is the first true indication your thyroid gland is not functioning properly and needs to be treated immediately to return you back to normal health again.

The TSH test

This is the preferable way to see how well your own thyroid gland is functioning. The test will show if you have an under active thyroid gland- which is known as hypothyroidism, or if you have an over active thyroid gland- which is known as hyperthyroidism. The test is very simple and pain free. A blood test is all that is required from you which takes less than a minute.

Along with the TSH test you may also have to take a T3 and a T4 test.

The T4 Test
The T4 test has been used for many years to further evaluate the thyroid function and help diagnose hyper and hypothyroidism by testing for the amount of Thyroxine, or T4 in the body. The T4 test is also used on newborns to test for hypothyroidism. Symtoms of hypothyroidism include weight gain, mood swings, extreme tiredness, low sex drive and constant lack of energy. Thyroxine is 1 of the 2 major hormones the thyroid gland produces, the other being triiodothyronine, or T3.

The T3 Test
If a patient shows high TSH levels a T3 test will be done to make further evalutations. The T3 test is used to help diagnose hyperthyroidism by looking for the amount of triiodothyronine, or T3, in the body. This hormone controls the rate at which the body uses energy. If the thyroid is producing excessive amounts of T4 and T3 the patient may show signs of hypertyroidism. Symtoms include nervousness, weight loss, shaking hands, insomnia, and puffy dry and irritated eyes. In some cases a patient may have restrictions in eye movement giving the appearance of staring, other times the eyes may bulge.

How Thyroid Production Works
The human body has an intricate feedback system that very cleverly turns the thyroid hormone production on or off. When the level of T4 (thyroxine) in the body decreases, an organ in the brain called the hypothalamus releases a hormone called thyrotropin which then stimulates the pituitary gland to release the thyroid-stimulating-hormone (TSH) which in turn stimulates the thyroid to make more or less T4. When the concentration of T4 levels in the blood, TSH release is stopped.

T4 makes up nearly 90% of all hormones produced by the thyroid, with T3 making up less than 10%. Inside the gland T4 is bound to a protein called thyroglobulin. When it is needed, the thyroid gland releases stored T4 into the body. When T4 is in the blood it is either free, meaning it is not bound with thyroglobulin, or protein-bound, meaning it is primarily bound to thyroxine-binding globulin.

T4 is converted into T3 when it enters the liver or other tissues. T3 can also by highly protein-bound, but it is only in the free form states that T3 and T4 become biologically active. Free T3 is also 4 to 5 times more active than free T4 in circulation.