Understanding the Thyroid Hormones

Hormones are substances produced in one organ transported to another organ through body fluids where in they produce an effect. Thyroid gland secretes such hormones to perform different functions depending on what organ the thyroid sends them to. There are two types of hormones that the thyroid gland produces the Thyroxine (T4) and Triiodothyronine (T3). The most active of the two hormones is T3 while T4 only gains it's potency only after it is converted to T3.  A hormone produced in the pituitary gland is called Thyrotropin or Thyroid Stimulating Hormone (TSH). It stimulates the thyroid gland to produce thyroid hormones (T3 and T4). TSH is regulated by hypothalamus gland, a part of the brain responsible for regulating body temperature, thirst and hunger.

Each hormones have their own functions in the body. Thyroxine (T4)  increases the heart rate, the basal metabolic rate and improves brain development. Triiodothyronine (T3)  increases the body's ability to consume oxygen for the production of energy, increases the metabolic rate and stimulates the rate of protein synthesis in the body. While TSH plays a vital role in managing the efficient functioning of the human body.

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Imbalances in the thyroid gland are detected by these hormones. It is a must to measure the levels of these hormones to know the condition of the thyroid. Here are some of the basic test to evaluate the function of the thyroid gland:

T4 Test -  Thyroxine is most attached to a protein called thyroxine-binding globulin. To see the levels of both free and bound thyroxine, this test is appropriate.

T3 Test - A test that measures both bound and free triiodothyronine. T3 has a greater effect on the way the body uses energy than T4, even though T3 is normally present in smaller amounts than T4.

Free Thyroxine (FTI or FT4) - A direct measurement of free or unbound thyroxine.

Free Triiodothyronine (FTI or FT4) - A direct measurement of free or unbound triiodothyronine.

TSH Test - A test that initially test the thyroid function is TSH.

These tests were done through blood testing and may be done throughout the day without fasting. It is best to consult your doctor first before subjecting yourself through these tests.