What is the purpose of a Thyroid Test?
Thyroid test is a common medical phenomenon. The Thyroid test, also commonly known as the thyroid function test, tests the functioning of the thyroid gland. These tests are important to keep a check on the health of the thyroid gland and consecutively, your whole body.
Importance of Thyroid Gland
Thyroid is a gland in our body which is responsible for regulating many an important functions of our body. The thyroid gland secretes thyroid hormones T4 (Thyroxine) and T3 (Triiodothyronine). Thyroid hormones are responsible for regulating our body’s metabolic functions.
Our metabolic processes consist of all the processes happening inside our body that keep us alive. This includes respiration, digestion, conversion of food into energy, heart-rate, the way our body utilizes energy from the food, etc. Therefore, people with an abnormally functioning thyroid will experience fluctuations in these processes, which may directly impact their quality of life.
What is Thyroid Test
Thyroid tests are done to check the functioning of the thyroid gland. Therefore, it is important to understand the functioning of the thyroid gland in order to understand what thyroid test is and what it checks for.
How Thyroid Gland Functions
Thyroid secretes T3 and T4 hormones which stimulate various metabolic processes in our body. The TSH (Thyroid Stimulating Hormone), which is released by the pituitary gland, stimulates the thyroid gland to release these hormones when required. Not just that, the pituitary gland itself is stimulated by TRH (Thyrotropin Releasing Hormone) which is secreted by the hypothalamus gland located in the brain.
Thyroid Disorders are caused when there is an under secretion or an over secretion of the thyroid hormones. This fluctuation in the level of hormones leads to disturbance in the normal functioning state of the human body. Since the secretion of thyroid hormones is dependent on pituitary, hypothalamus, and thyroid glands, the increase or the decrease in the hormone level could be because of an issue in one or more of these glands.
Purpose of the Thyroid Test
The main reason for conducting a thyroid test is to diagnose if any thyroid disorders exist. Thyroid disorders can be of various types and each has its own characteristic symptoms.
Hypothyroidism is a disease where the Thyroid Gland is under-active. This leads to lower secretion of the Thyroid Hormones, thus leading to a slower metabolism, unexplained weight gain, depression, puffy face, lower heart rate, fatigue etc. Thyroid function tests are conducted to check the level of thyroid hormones in the blood stream.
In Hyperthyroidism, the thyroid gland is overactive, leading to an over-secretion of the thyroid hormone. This leads to an elevated rate of metabolism, higher heart rate, anxiety, loss of sleep, unexplained weight loss, fatigue, protruding eyes, etc. Doctors check the level of thyroid hormones in the bloodstream to confirm the existence of hyperthyroidism.
Other issues of the thyroid gland include Goiter, Thyroid Cancer, Thyroid Nodules, and Thyroid Storm. The confirmation of these disorders require various tests and examinations like ultrasound, CT Scan (CAT Scan), Fine Needle Aspiration (FNA), Physical Exam, Radiation Test etc. Thyroid Function Tests are also done to support and confirm the existence of these issues.
Thyroid Function Test
The Thyroid Function Tests, also simply known as Thyroid tests, are blood tests done to ascertain the health and disorders of the Thyroid Gland. There are various Thyroid Function Tests. A doctor will suggest at least one or a combination of one or more Thyroid functions tests to get a proper diagnosis of your thyroid.
Thyroid Function Tests are basically of the Following Types:-
TSH (Thyroid Stimulating Hormone) Test is a Thyroid Function test that measures the amount of TSH in the blood. Thyroid Stimulating Hormone (TSH) is released by the pituitary gland. It is like an alarm that sirens the thyroid gland to release its hormones, and at the same time also regulates the amount of thyroid hormones to be released.
If the TSH Thyroid test results show elevated levels of TSH, then it may signify that the thyroid gland is secreting fewer thyroid hormones. It may indicate the possibility of hypothyroidism, i.e, under-active thyroid. Similarly, decreased levels of TSH hormone in the blood stream may indicate an over-active thyroid (Hyperthyroidism).
Additional thyroid function tests are performed on the patient for further diagnosis and confirmation.
T4 (Thyroxine) is an important hormone released by the thyroid gland. It regulates the metabolic processes in our body and is found in two forms – Free and Bound. Free T4 enters the bloodstream and affects the tissues and organs it enters. T4 that is bound to proteins is prevented from affecting the tissues and organs.
The Thyroid Function tests that measure the amount of Free T4 are very important in thyroid disorder diagnoses. They are known as the Free T4 (FT4) and the Free T4 Index (FT4I or FTI) Thyroid tests. Thyroid Test results showing elevated amounts of Free T4 may indicate Hyperthyroidism (over-active thyroid) and decreased amounts may indicate Hypothyroidism (underactive thyroid).
Triiodothyronine (T3) along with T4 are thyroid hormones that collectively regulate our metabolism. T3 is a more active hormone, and T4 is converted into T3 by the liver or some other organs. A hyperthyroid patient has elevated T3 levels.
T3 Thyroid Function Tests can be of two types – Free T3 Test or Total T3 Test. Just like T4, T3 also binds itself to protein. If the T3 levels in a Free T3 tests are elevated, it may be a strong indication of hyperthyroidism. Decreased levels of T3 may be an indication of hypothyroidism.
This is a thyroid function test that is performed along with other thyroid tests to confirm or evaluate the thyroid disorder in the patient. T3RU means T3 Resin Uptake. This blood test measures TBG (Thyroxine Binding Globulin), the protein that the thyroid hormones bind them to.
Elevated or decreased levels of T3RU Thyroid function test, along with the test results of T4 and T3, may help the doctore in a better diagnosis of the thyroid disorder.
Thyroid Antibodies Test (TPOAb)
TPOAb or Thyroid Peroxidase Antibodies Test is a Thyroid function test that helps doctors in investigating the cause of thyroid disorders in thyroid patients. Antibodies are produced in our bodies to fight against foreign invading substances that may be harmful to our body. However, sometimes antibodies start to attack a tissue or an organ, causing an auto-immune disease.
The two types of antibodies that may attack the thyroid gland are Peroxidase and Thyroglobulin. If a Hyperthyroid patient’s thyroid antibodies test result shows positive, it may be an indication of an auto-immune disease. A hypothyroid patient having positive result on this Thyroid antibodies test could have Hashimoto’s thyroiditis.
How is Thyroid test done
Blood samples of the patient are collected in a thyroid test and then tested in a lab. For an accurate diagnosis of the thyroid disorder, the doctor will not rely on a single thyroid test but ask for a combination of various thyroid function tests. Let us discuss why this is important by taking an example.
The TSH results of a patient suffering from hyperthyroidism will show decreased levels of TSH, indicating an issue with the thyroid gland or the pituitary gland. However, sometimes, the level of T4 hormone in the blood test is normal when the FT4I thyroid test is performed. Therefore, another thyroid function test (in this case free T3 thyroid test) is asked for. An elevated level of T3, even though level of T4 is normal, may indicate a case of hyperthyroidism.
Thyroid Test at Home
If you have had a TSH thyroid function test done, chances are that your results may be well within the thyroid blood test normal range. However, this result is still not conclusive. If you suspect that you may have thyroid issues, you can do a small thyroid test at home.
Thyroid test at home can only give you an idea whether you might or might not have a thyroid problem. It’s not completely conclusive and you can’t solely rely on it. You should ideally get additional thyroid function tests like FT4I, Free T3, and thyroid antibodies tests done for a better diagnosis.
Thyroid Test at Home procedure
There are a couple of thyroid test at home procedures you can follow to check your thyroid.
Thyroid Test at Home to check Enlargement of Thyroid
Take a good look at your neck in front of a mirror and check if there is a swelling. After that, swallow and eatable. If you see that a swollen part at the base of the neck protrudes out, it may be because of an enlarged thyroid.
Basal Temperature Thyroid Test at Home
The second and more conclusive thyroid test at home is to measure your basal body temperature for five consecutive days.
Keep a basal thermometer ready at your bedside. If you have a mercury thermometer, make sure you shake it down to a 95 degree F before the measurement. You can use an accurate digital thermometer for this thyroid test at home.
For five days, measure your body temperature. Make sure that you do not get out of bed or even move your back as it may set your thyroid gland into motion. Therefore, keep the temperature by your side only.
The thyroid test at home normal range is 97.8-98.6 degree. If your temperature is a couple of degrees above or below this range consecutively, it may be a sign of a thyroid issue. Make sure that you aren’t suffering from infections or going through menstrual cycle during the time of measurement.
Thyroid Blood Test procedure
The thyroid blood test procedure consists of collection of a patient’s blood sample with a syringe. Then, the sample is tested in a lab to see if the thyroid hormone level is between the thyroid blood test normal ranges. If the level of the hormones is lower or higher, it may indicate a complication with the thyroid gland.
The procedure is fairly similar to any other blood test. You can either go to the doctor’s office or to the pathological lab for blood sample collection. You can also have an expert come to you for a thyroid test at home blood sample collection.
It is important for you to tell your doctor about any medications you may be taking. These can include hormone affecting drugs like thyroid hormone medicines, birth control, estrogen, etc. You may have to temporarily stop taking these medicines. You will also have to tell your doctor if you’re pregnant or taking steroids.
Thyroid Blood Test Venipuncture
When you go for a thyroid test, the doctor will collect your blood sample using the venipuncture technique. Venipuncture technique involves extracting a blood sample from a patient’s blood vessel via a syringe. The doctor/lab expert will take the necessary amount of blood to test if your levels are in the thyroid blood test normal range.
After collection of the blood sample, the lab expert will remove the syringe and apply pressure on the extraction point. He may also temporarily put a bandage on it. However, you can resume your regular daily routine immediately.
Thyroid Blood Test Normal Range
Thyroid Blood Test Normal Range is different for different age groups and people. Let us look at them:-
TSH Thyroid Blood Test Normal Range
TSH Thyroid Blood Test Normal Range (for babies with premature birth – 28 weeks) – 0.7‑27 mIU/L
TSH Thyroid Blood Test Normal Range (children)
- 1 Week – 1‑39 mIU/L
- 2‑20 Weeks – 1.7‑9.1 mIU/L
- 21 weeks to 20 years – 0.7‑64 mIU/L
TSH Thyroid Blood Test Normal Range (adults)
- 21‑54 years – 0.4‑4.2 mIU/L
- 55‑87 years – 0.5‑8.9 mIU/L
TSH Thyroid Blood Test Normal Range (Pregnant Women)
- First trimester – 0.3‑4.5 mIU/L
- Second trimester – 0.3‑4.6 mIU/L
- Third trimester – 0.8‑5.2 mIU/L
Thyroid Blood Test Normal Ranges for other Thyroid Function Tests
|Total T4 (Thyroxine) T4 Tests||4.5-12.5 µg/dL|
|Free T4 (Free Thyroxine) FT4||0.8-1.8 ng/dL|
|Total T3 (Triiodothyronine) T3 Tests||80 -200 ng/dL|
|Free T3 (Free Triiodothyronine) FT3 Tests||2.3- 4.2 pg/mL|
|RT3 (Reverse T3/Reverse Triiodothyronine)||10-24 ng/dL|
|TPOAb (Thyroid Peroxidase Antibodies)||0-35 IU/mL|
|TSI (Thyroid stimulating Immunoglobulins)||0-1.3|
|Tg (Thyroglobulin)||Thyroid gland removed: 0-0.1 ng/ml.
Thyroid Gland present: 0-33 ng/mL
|TgAb (Thyroglobulin Antibodies)||0-4.0 IU/mL|
Thyroid Antibodies Test
Doctors use Thyroid Antibodies Test results to ensure whether a thyroid disease is the result of an autoimmune disorder.
What is an autoimmune disorder?
Our immune system automatically produces blood proteins known as antibodies to fight with any foreign substances or toxins that enter our body. However, antibodies may sometimes start to attack tissues in the body causing damage and inflammation in those specific organs, causing an autoimmune disorder.
Why is Thyroid Antibodies Test Done?
There are certain antibodies that might start attacking thyroid tissue. This causes inflammation in the thyroid gland and also interferes with the secretion of the thyroid hormones. Therefore, doctors ask patients for a thyroid Antibodies test. The results of the thyroid antibodies test reveals whether the Goiter, hyperthyroidism, hypothyroidism, Grave’s disease, or Hashimoto’s thyroiditis is not the result of an autoimmune disorder.
Types of Thyroid Antibodies Tests
- TPOAb (Thyroxine Peroxidase Antibodies): TPOAb test is the most common Thyroid Antibodies Test and is also known as Antithyroid Microsomal Antibody Test. This antibody destroys Thyroid Tissue and may cause Hashimoto’s Thyroiditis (Hypothyroidism) or Grave’s disease (Hyperthyroidism).
- TGAb (Thyroglobulin Antibody): TGAb thyroid antibodies test is done on patients to test whether Thyroglobulin antibody is destroying their Thyroglobulin. The thyroid gland stores its thyroid hormone in the form of Thyroglobulin in the gland.
- Thyroid Stimulating Hormone Receptor Antibodies (TSHRAb): TSH Receptor Antibodies attack the protein receptors that bind the TSH released from the pituitary gland. They are of two types – TSI (thyroid Stimulating Immunoglobulin) and TBII (Thyroid Binding Inhibitory Immunoglobulin). TSI causes hyperthyroidism while TBII causes hypothyroidism. TSI tests help doctors in diagnosing Grave’s disease while they do not generally prescribe a TBII test.
Thyroid Profile Test
All the blood tests done to get a detailed profile of the functioning of the thyroid gland are collectively known as a thyroid profile test. This test includes:-
- TSH (thyroid Stimulating Hormone) Test
- Total T4 (Total Thyroxine) Test
- Free T4 (FT4) Test
- T3 (Tri-iodo-thyronine) Test
- Free T3 Test
The complete Thyroid Profile test is essential for infants, children, pregnant women, and women who have just become a mother. You should also go for a Thyroid Profile test if you have been experiencing unusual and unexplained weight loss or gain, fatigue, irregular menstrual cycle, anxiety, trouble loosing or gaining weight etc.
How to read Thyroid Test
While reading and interpreting a thyroid test result, you have to consider the thyroid blood test normal ranges. Major fluctuations from the thyroid blood test normal range may indicate hyperthyroidism or hypothyroidism.
Most endocrinologists rely on the thyroid blood test normal ranges of the TSH Test. An increased amount of TSH may indicate hypothyroidism and a decreased level may show hyperthyroidism. However, the doctor may also suggest additional tests such as T4 and T3 for further diagnosis of the root cause of the thyroid issues.
Increased levels of T4 and T3 along with low levels of TSH suggest with reference to the thyroid blood test normal ranges may suggest hyperthyroidism. Decreased levels of T4 and T3 along with increased levels of TSH with reference to the thyroid blood test normal range may suggest hypothyroidism.
You doctor may ask for additional thyroid antibodies test to check if the problem is a result of an autoimmune disorder or not.
T3 & T4 Test and Test Results
Many endocrinologists prefer relying on TSH tests to start a treatment for thyroid disorders. However, endocrinologists also ask for T4 and T3 test results to help with further diagnosis of the causes behind the thyroid problem.
Thyroxine Hormone (T4) has two tests – Total T4 and Free T4. Free T4 thyroid test is a routine test. Sometimes, T4 levels are within the thyroid blood test normal range even when the patient is suffering from hyperthyroidism.
Sometimes, some patients have disturbed levels of TSH while the Free T4 in their blood is normal. Therefore, the doctor uses a triiodothyronine (T3) thyroid test to measure the level of T3 hormone in the blood. Blood test results showing that T3 levels are increased and the TSH levels are low may indicate hyperthyroidism.
Thyroid Test for Thyroiditis
Patients experiencing symptoms of hypothyroidism may have Hashimoto’s disease or Thyroiditis. Hashimoto’s thyroiditis is an autoimmune disorder.
Your doctor will ask you for a TSH test to check if your TSH levels are high. After that, doctors look at TPO Ab Test results to check if your hypothyroid condition is because of Thyroxide Peroxidase antibodies. If the test results positive, you may have thyroiditis.
Thyroid Test for Thyroid Storm
The heart rate, respiration, and the rate of all the other metabolic processes in a person suffering from thyroid storm are extremely elevated. Therefore, a doctor will quickly run Thyroid function tests such as TSH, FT4I, and Free T3 tests to diagnose a thyroid storm.
Thyroid storm is a fatal condition. A patient suffering from thyroid storm needs immediate medical attention in an ICU (Intensive Care Unit). Most of the times, the doctor will proceed with a treatment for Thyroid Storm on the patient without even waiting for the thyroid test results.
Thyroid Test for Thyroid Nodules
Thyroid nodules are lumps and overgrowth that happen in the thyroid gland. Nodules are common among people and are usually harmless. However, some nodules can become cancerous leading to thyroid cancer, while other nodules can also start secreting thyroid hormones independently, leading to hyperthyroidism.
To test for thyroid nodules, a doctor will first do some thorough physical examinations. These exams include CT scan, ultrasound of the thyroid, and FNA (Fine Needle Aspiration). Additionally, he may also suggest some thyroid function tests like TSH, FT4I and T3 tests to check the functioning of the thyroid too.
A doctor will check the images of the thyroid gland using ultrasound technique to check the presence of thyroid nodules as well as their behavior. They will use a Fine Needle guided by ultrasound to extract some nodule cells to check if they are cancerous or not. Abnormalities in the thyroid tests may also reveal whether the nodules have become ‘hot’ and are causing hyperthyroidism.
Thyroid Test for Papillary Thyroid carcinoma
Papillary Thyroid Carcinoma is a kind of Thyroid Cancer which is most commonly found among thyroid cancer patients. Thyroid test for papillary thyroid carcinoma is similar to the thyroid tests for thyroid nodules.
Whenever a doctor is testing a thyroid for cancerous cells, they use an ultrasound guided fine needle aspiration to extract cells from the thyroid nodule and check if they are cancerous or not. Apart from that, a doctor also uses ultrasound imaging to check the size and behavior of thyroid nodules. Solid nodules can be cancerous while thyroid nodules filled with fluids are not generally cancerous.
Cost for Thyroid Test
The cost for thyroid test varies from lab to lab and from doctor to doctor. Some pathological labs may charge a lesser amount than the others for the same tests.
TSH Test is the most common thyroid test suggested by doctors. Its cost may lie anything between Rs 100 to Rs 600, varying from lab to lab. The average cost for TSH thyroid test is around Rs 250. Other tests like TPO Ab (Thyroid Peroxidase Antibody Test) may cost between Rs 1000 and Rs 1500.
Free T4 test costs around Rs 300 – Rs 500. Antithyroglobulin Antibody test (Anti TG Ab) also costs between Rs 1000 and Rs 1500.