You and your Thyroid

The thyroid is a butterfly-shaped gland whose name comes from the Greek word for "shield." It is a small gland that weighs less than an ounce and sits at the base of your neck below your Adam’s Apple. The thyroid's job is to make thyroid hormones, which are secreted into the blood and control your metabolism—the process of converting food into energy. Thyroid hormones help the body use energy, stay warm, and keep the brain, heart, muscles, and other organs doing their jobs as they should.  The thyroid gland is part of the endocrine system, which includes all the glands in your body that regulate essential functions. The thyroid gland makes hormones called T3 and T4 that regulate your breathing, heart rate, muscle strength, body temperature, and many more functions. Thyroid tests are used to check your thyroid levels.

When your body makes too much thyroid hormone, it is like putting your metabolism’s pedal to the metal. Speeding up your energy may sound good but expediting your body metabolism has adverse effects like rapid heartbeat, anxiety or nervousness, weight loss, sweating, shaking movement in your hands or fingers, bad sleeping, as well as heat sensitivity. Hyperthyroidism can be hard to diagnose as all these symptoms are common in many other diseases and conditions. On the other hand, when your body does not make enough thyroid hormone—in hypothyroidism, you may also feel fatigued, but may also feel other symptoms, including slow heart rate, weight gain, cold sensitivity, memory loss, muscles weakness, joint stiffness, swollen face, and other unpleasant conditions. Like many things in life, too much or too little does not keep your body in balance. To check both hyperthyroidism and hypothyroidism, thyroid tests and mainly a thyroid function test can help to diagnose your thyroid dysfunction.

The major thyroid hormone secreted by the thyroid gland is thyroxine, also called T4, because it contains four iodine atoms (a chemical element with the symbol I). To expand its effects, T4 is converted to triiodothyronine (T3) by the removal of an iodine atom. This occurs mainly in the liver and in certain tissues where T3 acts, such as in the brain. The amount of T4 produced by the thyroid gland is controlled by another hormone called Thyroid-Stimulating Hormone or TSH. This hormone is made in the pituitary gland, which is located at the base of the brain. An at-home TSH test can be the best way to initially assess your thyroid function. Changes in TSH can happen before the level of thyroid hormones in the body becomes too high or too low and serve as an early warning sign. In most healthy individuals, a normal TSH level means that the thyroid is functioning properly. A low TSH may result from a problem in the pituitary gland, which prevents it from making enough TSH to stimulate the thyroid. This condition is often called secondary hypothyroidism.

For a complete thyroid function test, additional thyroid tests are needed, a Total T4 measures both bound and free hormone. A Free T4 (FT4) measures what is not bound and able to enter and affect the body tissues– A test including FT4 more accurately reflects how the thyroid gland is functioning when checked with a TSH—The finding of an elevated TSH and low FT4 indicates hypothyroidism, while a low TSH and low FT4 indicates hypothyroidism. A T3 test can be used to diagnose hyperthyroidism, but its main value is to determine the severity of hyperthyroidism. T3 testing rarely is helpful in hypothyroidism since it is the last test to become abnormal. Someone can be severely hypothyroid with a high TSH and low FT4 but still have a normal T3. Measurement of free T3 (FT3) is possible but is often a less reliable parameter.

A thyroid panel test is used to detect the level of the TSH, FT4, FT3 hormones. Thyroid peroxidase (TPO) is an enzyme normally found in the thyroid gland. TPO plays an important role in the production of thyroid hormones. A TPO test detects antibodies against TPO in your blood which may suggest that the cause of your thyroid disease is an autoimmune disorder, such as Hashimoto's disease or Graves' disease. Some Thyroid panel tests also include Thyroglobulin (Tg), which is a protein produced by normal thyroid cells and thyroid cancer cells. It is not a measure of thyroid function, and it does not diagnose thyroid cancer when the thyroid gland is still present. It is used most often in individuals who have had surgery for thyroid cancer to monitor them after treatment. Last but not least is an iodine test which also can be ordered at home. Because T4 contains iodine, the thyroid gland must pull a large amount of iodine from the bloodstream to make an appropriate amount of T4, and this test can check if there is enough iodine for this process.

Finally, it’s important to remember that abnormal tests do not necessarily mean a thyroid disorder is present, as each test can be affected by a variety of factors, like other medications you are using. Once you get your test results, talk with your doctor as diagnosing thyroid disorders can be tricky.