TSH blood test
A TSH blood test is indicative of the increased or decreased levels of Thyroid stimulating hormone. A thyroid TSH test detects the imbalances in thyroid gland hormone output. A TSH blood test is normally done for diagnosing hypothyroidism, a condition in which the thyroid gland produces fewer hormones than the body needs. The TSH test measures the body's thyroid hormone output level of the thyroid gland. A TSH test is prescribed for a person of any age, male or female with suspected hypothyroid. The normal range of TSH test for an adult is 0.4 - 5.5 mU/ml. TSH gets increased in case of hypothyroid. The test result gets decreased with hyperthyroid. No single laboratory test is 100% accurate in diagnosing different types of thyroid disease. A combination of two or more thyroid tests is normally employed to detect the abnormality of thyroid function.
Thyroid is a gland in the neck overlying the windpipe that regulates the speed of metabolic processes by producing a hormone with the eponymous name thyroxin. Thyroid is an endocrine gland. The thyroid gland which resembles a butterfly, sits astride the trachea. Its secretion - thyroxin, a hormone that regulates the metabolic activity of the body. Too much thyroxin races the metabolism resulting in weight loss, temperature elevation, nervousness and irritability. On the other hand, too little thyroxin slows down the metabolism rate resulting in deep voice, weight gain and water retention. This can result in retardation in physical growth and mental development in children. Both conditions equally affect hair and skin growth, bowel function and menstrual flow.
The thyroid gland is often enlarged whether it is secreting too much hormone, too little or even when it is functioning normally. The thyroid is controlled by the pituitary gland, which secretes Thyroid Stimulating Hormone (TSH) in response to the amount of thyroxin in the blood. TSH increases the amount of thyroxin secreted by the thyroid and also causes the thyroid gland to grow.
Hyperthyroid Goiter : If the amount of TSH is high, the thyroid will both enlarge and secrete too much thyroxin. The result is termed as Hyperthyroidism with a goiter. Graves' disease is the most common form of this disorder.
Euthyroid goiter : If dietary iodine is insufficient, too little thyroxin will be secreted and the pituitary will sense the deficiency and produce more TSH. The thyroid gland will enlarge enough to make sufficient thyroxin.
Hypothyroid goiter: If dietary iodine is severely low, even an enlarged gland will not be able to make enough thyroxin. The gland may keep growing under the influence of TSH, but it may never make enough thyroxin.
An endocrinologist who specializes in the endocrine system can also be consulted for thyroid problems and diseases. Specialists who deal with thyroid problem are called thyroidologists. Thryoidologist and endocrinologist are specially trained doctors who diagnose and treat diseases affecting the thyroid gland. A thyroid specialist continues specialized education focused on thyroid issues after obtaining a Masters degree in medicine. He is qualified and trained to treat conditions that are complex and involve many systems within the body that may be affected due to thyroid imbalance.
A primary care doctor too often misses the diagnosis of a thyroid disease. Sometimes primary care doctors refer patients to a thyroid specialist when there is problem in the endocrine/ hormone systems. Thyroid specialists treat patients with too much or too little thyroid hormone. The thyroid specialist helps the patients to reach a hormone balance by replacing or blocking thyroid hormone. Thyroid specialists also receive special training to manage patients with thyroid growths or thyroid cancer and enlarged thyroid glands. There are times when the services of a thryoidologist or an endocrinologist become absolutely necessary.
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.
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Collection of Pages - Last revised Date: December 10, 2019