A T3 immunoassay test helps to determine whether the thyroid is functioning properly. It is primarily done to diagnose hyperthyroidism. T3 is also done to monitor the progress of a patient with a known thyroid disorder. T3 test is also sometimes conducted along with thyroid antibodies test to diagnose diseases such as Graves' disease, which is an autoimmune disorder that is the most common cause of hypothyroidism. Most of the T3 in the blood is attached to the thyroxine binding globulin. Only less than 1% of the T3 remains unattached. A T3 blood test is used to measure both the bound and the free Triiodothyronine. Increased or decreased T3 test result indicates that there is an imbalance between the body's requirement and supply of the hormone. If a patient is being treated with anti-thyroid medication for hyperthyroidism and the T3 is normal, then it is likely that the medication is controlling the condition. If the T3 is elevated, then the medication is not sufficient and the patient may be experiencing symptoms associated with hyperthyroidism. The normal test value for T3 is 100 to 200 ng/dL (nanograms per deciliter).
The T4 immunoassay test helps measure the amount of Thyroxine or T4 in the blood. A T4 immunoassay test is primarily done in response to an abnormal TSH result. Sometimes T4 is done along with TSH blood test. Thyroid hormone screening is commonly performed in newborns in the US as part of newborn screening programs for congenital hypothyroidism which may cause mental retardation if left untreated. False positive results can occur when testing a newborn for congenital hypothyroidism. Therefore normally the test is repeated a few days after initial testing. If the results continue to be abnormal, then additional testing is done. The normal range of a T4 test for an adult is 5 - 11 ug/dL (nanograms per deciliter).
There are other thyroid tests that indicate a malfunction. One such test is the 'Thyroid antibodies' test. This test is used to measure the presence of antibodies against thyroid tissue. Antibodies mean that the person has autoimmune disease such as Hashimoto's Thyroiditis or Graves' disease ( a condition characterized by an enlarged thyroid gland, weight loss without loss of appetite, sweating, heart palpitations, nervousness and inability to tolerate heat).
Thyroxine-binding globulin (TBG) is another thyroid test which detects the TBG which is an important protein in the blood that carries the thyroid hormones T3 and T4. This is a rare test and not done very commonly. Other diagnostic tests that are used to investigate problems with thyroid gland are the thyroid scan, thyroid ultrasound and thyroid biopsy.
Hyperthyroidism is a condition that occurs when there is too much thyroid hormone in the body. The hormones thyroxine and tri-iodothyronine are produced by the thyroid gland and play a major role in determining the body's metabolic rate. When there is excess amount of thyroid hormones, it will lead to a faster metabolism resulting in hyperthyroidism. Hyperthyroidism occurs when thyroid cells trap excess iodine and produce excessive thyroid hormone. Sometimes the cause is damaged or inflamed thyroid cells. A person suffering from hyperthyroidism experiences excessive sweating and rapid heart rate (palpitations) and tremors. Such persons may notice loss of weight and extreme fatigue. These symptoms appear gradually and may sometimes go unnoticed. A person suffering from hyperthyroidism may feel nervous and notice muscle weakness. Women who are suffering from hyperthyroidism tend to have light menstrual periods or may even miss few cycles. Hair becomes brittle and skin becomes warm and moist. A person may appear agitated and confused. Patients suffering from hyperthyroidism often notice swelling at the base of the neck.
Thyroid Scan is used to measure the activity of the thyroid gland with radioactive substance. The blood TSH levels are measured to check for increased production of thyroid hormone. Graves Disease is an autoimmune disease that results in an overactive thyroid gland. This in turn leads to hyperthyroidism. Thyroiditis or inflammation of the thyroid gland is yet another cause for hyperthyroidism. Goiter or toxic nodule on the thyroid gland can be another cause for hyperthyroidism.
Anti thyroid drugs are used to control the production of thyroid hormone. These drugs include methimazole (Tapazole) and propylthiouracil (PTU). Radioactive Iodine treatment for hyperthyroidism involves a pill or liquid that is administered to the patient so as to ablate a hyperactive gland. Radioactive iodine therapy destroys only local cells and is generally given as a one-dose treatment. It is essential to monitor this treatment since it may lead to destroy too many thyroid cells and even lead to hypothyroidism. This treatment for hyperthyroidism is not used on pregnant or lactating women. Surgery is used to remove thyroid gland but this procedure is not without possible complications. Removal of too much tissue leads to hypothyroidism and often nerves connected with the vocal chords might be affected.
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Collection of Pages - Last revised Date: December 4, 2022