What Is a Thyroid Test?
Your thyroid gland is a small butterfly-shaped gland that is located just below your Adams apple or larynx in your throat. This gland has two lobes that lie near the windpipe or trachea. They are joined together by a narrow band of thyroid tissue, known as the isthmus. If the thyroid gland is not functioning properly you could develop health problems. The thyroid can be underactive or overactive. There are certain tests your doctor can perform to make sure your thyroid is functioning normally.
Other People Are Reading
-
Identification
-
The function of the thyroid gland is to convert the iodine in the foods you eat into thyroid hormones, thyroxine or T4 and triiodothyronine or T3. These hormones are released into the bloodstream, where they help to control your metabolism. Every cell in the body depends upon these thyroid hormones to properly regulate their metabolism. When the level of thyroid hormones is too low, TSH or Thyroid Stimulating Hormone, is produced to encourage the thyroid gland to produce more hormones. When the level of these hormones becomes too high in the blood, TSH levels are decreased. Thyroid tests are performed through a simple blood draw --- and can help to determine the level of T3, T4 and TSH in the bloodstream.
TSH Tests
-
The first thing your doctor will usually check is the level of TSH in your blood. A normal TSH value means that the thyroid is functioning correctly. If your TSH levels are high your thyroid gland might be failing to produce enough hormones. This condition is called hypothyroidism. When your TSH levels are low, then your thyroid gland could be producing too much thyroid hormones in a condition called hyperthyroidism. A normal TSH range is approximately 3.0 to 5.0 uU/ml.
-
T4 Tests
-
The hormone T4 circulates in the blood by binding to proteins or by floating freely. The blood level of the free T4 is often used to determine how the thyroid is functioning. A blood test will check your levels of Free T4 and the Free T4 Index. If you have hypothyroidism, these levels will be elevated. If you have hypothyroidism, the level of this hormones will be low. Healthy levels are between 4.5 to 11.2 mcg/dL.
T3 Tests
-
Testing the blood level of T3 can help to diagnose thyroid malfunction and to determine the severity of your condition. If your thyroid gland is overactive you will have an elevated T3 level. It is not one of the most commonly used tests, since you can have a highly underactive thyroid with a high TSH and low FT4, but still have a normal T3. The range for normal values of T3 is between 100 to 200 ng/dL.
Antibody Tests
-
Blood tests can also be done to detect the antibody thyroglobulin, which is a protein in the thyroid gland that plays a role in the production of thyroid hormones. Antithyroglobulin antibodies can damage the thyroid gland and affect its function. Testing your blood for the presence of antithyroglobulin antibodies can help to diagnose thyroid disorders. Normal blood tests show no presence of these antibodies.
Signs and Symptoms
-
Hypothyroidism can cause symptoms such as fatigue, forgetfulness, feeling excessively cold, constipation, dry skin, fluid retention, achy muscles and joints, depression and weight gain. Hyperthyroidism can cause symptoms of excessive sweating, heat intolerance, increased bowel movements, tremors or shakiness, agitation, rapid heart rate, weight loss and fatigue. There are many diseases associated with thyroid malfunction. Visit any of the web sites in Resources for more information.
-
Resources
- Photo Credit http://www.nlm.nih.gov/medlineplus/ency/imagepages/9970.htm
