Friday, September 22, 2023

Blood Test For Thyroid Function

How Is The Test Used

Thyroid Hormones and Thyroid Function Tests

A thyroid panel may be used to evaluate thyroid function and/or help diagnose thyroid disorders.

Typically, the preferred initial test for thyroid disorders is a TSH test. If the TSH level is abnormal, it will usually be followed up with a test for free T4. Sometimes a total T3 or free T3 will also be performed. Often, the laboratory will do this follow-up testing automatically. This is known as reflex testing and it saves the healthcare practitioner time from having to wait for the results of the initial test and then requesting additional testing to confirm or clarify a diagnosis. Reflex tests are typically performed on the original sample that was submitted when the initial test was requested.

As an alternative, a thyroid panel may be requested by your healthcare practitioner. This means that all three tests will be performed at the same time to get a more complete initial picture of thyroid function.

Tsh Response To Thyrotropin Releasing Hormone

For a variety of reasons, the measurement of TRH in serum as a test of thyroid function has not been generally achieved. A reliable assay would be of great clinical interest as it might provide a powerful means of distinguishing between various levels of dysfunction along the pituitaryhypothalamic axis.

Intravenous administration of TRH is followed by a measurable rise in TSH which peaks within 20 to 30 minutes. The TRH stimulation test is performed by giving 500 . If hyperthyroidism or primary hypothyroidism are diagnostic possibilities, samples are drawn at injection and 20 and 30 minutes afterward. The “flat line” response of hyperthyroidism and supranormal response of primary hypothyroidism will be evident at these time points . If pituitary or hypothalamic hypothyroidism is suspected, samples should be obtained at injection and 20, 40, 60, 90, and 120 minutes. These will illustrate the reduced response of pituitary hypothyroidism and the delayed response of hypothalamic hypothyroidism. Unfortunately, a fraction of patients with pituitary hypothyroidism have a delayed TSH release, so this finding is consistent with both pituitary and hypothalamic dysfunction. In females at any age, a normal peak response is greater than 5 U/ml. In males up to age 39, a similar value applies but after age 40, peak increases as small as 2 U/ml are found in some normal men.

TSH response to TRH in various types of hypothyroidism.

Preparing For The Tests

You dont need to do anything special to prepare for the thyroid function tests. If a healthcare professional has ordered other blood tests to be taken at the same time, you may need to fast for several hours before the test. They will let you know of any special instructions to follow.

Otherwise, you will not need to follow any specific directions before the test.

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Lab Tests Of Biopsy Samples

In some cases, doctors might use molecular tests to look for specific gene changes in the cancer cells. This might be done for different reasons:

  • If FNA biopsy results arent clear, the doctor might order lab tests on the samples to see if there are changes in the BRAF or RET/PTC genes. Finding one of these changes makes thyroid cancer much more likely.
  • For some types of thyroid cancer, molecular tests might be done to see if the cancer cells have changes in certain genes , which could mean that certain targeted drugs might be helpful in treating the cancer.

These tests can be done on tissue taken during a biopsy or surgery for thyroid cancer. If the biopsy sample is too small and all the molecular tests cant be done, the testing may also be done on blood that is taken from a vein, just like a regular blood draw.

What Do The Results Mean

Pin on Thyroid

Your TSH test results can tell you if your thyroid is making too much or too little thyroid. But the test can’t explain why your TSH levels may be too high or too low.

If your test results aren’t normal, your provider will probably order other thyroid blood tests to find out what’s causing your thyroid problem. These blood tests may include:

  • Thyroid antibodies test to help diagnose an autoimmune thyroid disorder, such as:
  • Graves’ disease, the most common cause of hyperthyroidism
  • Hashimoto’s disease, that the most common cause of hypothyroidism

In certain cases, an abnormal TSH result may be a sign of a pituitary gland problem, but this doesn’t happen often.

Learn more about laboratory tests, reference ranges, and understanding results.

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What Blood Tests Do Doctors Use To Check Thyroid Function

Doctors may order one or more blood tests to check your thyroid function. Tests may include thyroid stimulating hormone , T4, T3, and thyroid antibody tests.

For these tests, a health care professional will draw blood from your arm and send it to a lab for testing. Your doctor will talk to you about your test results.

Alteration Of Thyroid Function Studies In Hypothyroidism

Hypothyroidism most often is caused by glandular hypo-function. T4, T3 RU, free T4 index, free T4, and T3 fall within the normal range or are low . TSH and/or TRHTSH responsiveness are high. When pituitary or hypothalamic disease is at fault, the TSH may be low or normal. TRH-TSH responsiveness will be blunted in the case of pituitary disease or delayed and possibly exaggerated in hypothalamic and pituitary disease.

Thyroid Function Studies in Hypothyroidism.

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Normal Reference Range For Thyroid Function Tests

Reference ranges for each value under thyroid hormone is not consistent for everyone. It differs based on certain parameters such as age, health condition, and the laboratory that performs the testing.Common reference ranges for the thyroid panel are enlisted here:

  • TSH: 0.4 to 4.5 mIU/L
  • Free T4: Often falls between 0.8 and 1.5 ng/dL in adults.
  • Total T3: 75 to 195 ng/dL

Check your tsh test report or ask your doctor for the normal/reference range. Most laboratory reports mention the reference ranges applied to your thyroid test, however, consult an expert to interpret the results. Also, since it is a panel test, values are generally interpreted together and not seen as individual numbers.

Whats Included In A Full Thyroid Panel

Thyroid function test – Hypo and hyperthyroidism || symptoms & diagnosis

A full thyroid panel usually checks thyroid-stimulating hormone , triiodothyronine , and thyroxine levels. In some cases, a blood test for thyroid function will also check your bloodâs level of TPO antibodies. If you have abnormal thyroid hormone levels, high levels of TPO antibodies can point to an autoimmune thyroid disease as a possible reason for those abnormal levels.

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Tests For Thyroid Cancer

Thyroid cancer may be diagnosed after a person goes to a doctor because of symptoms, or it might be found during a routine physical exam or other tests. If there is a reason to suspect you might have thyroid cancer, your doctor will use one or more tests to confirm the diagnosis. If cancer is found, other tests might be done to find out more about the cancer.

Strategy For The Diagnosis Of Hyperthyroidism

Hyperthyroidism presents in remarkably diverse ways. On the one hand is the anxious young woman with classic signs and symptoms, while on the other is an elderly male with only goiter and proximal muscle weakness. In the former, a confirmatory test is adequate in the latter, a number of equivocal tests may necessitate protracted follow-up or a therapeutic trial. In either event, it is critical to establish the diagnosis of hyperthyroidism. is intended to offer guidance to the physician seeking to diagnose hyperthyroidism. It will not replace thorough knowledge of the patient, nor can it be a substitute for rigorous thinking.


If the studies are equivocal, a therapeutical trial may be warranted. Time permitting, repeated observations and testing at monthly intervals will often be diagnostic.

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Completing A Home Test

  • Drink a glass of water. Being well hydrated will make it easier to collect your sample.
  • Shower before you take your test or run your hands under warm water for a few minutes, as heat improves blood flow.
  • Do some light exercise to get the blood flowing.
  • Make sure your arm is below your heart level let gravity do some of the work.
  • Nails that are too long can make it difficult to collect a sample.

What Imaging Tests Do Doctors Use To Diagnose And Find The Cause Of Thyroid Disease

Thyroid Function Test Normal Range / Thyroid Function Tests And Their ...

Your health care professional may order one or more imaging tests to diagnose and find the cause of thyroid disease. A trained technician usually does these tests in your doctors office, outpatient center, or hospital. A radiologist, a doctor who specializes in medical imaging, reviews the images and sends a report for your health care professional to discuss with you.

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What Is Reverse T3

Reverse T3 is a biologically inactive form of T3. Normally, when T4 is converted to T3 in the body, a certain percentage of the T3 is in the form of RT3. When the body is under stress, such as during a serious illness, thyroid hormone levels may be outside of normal ranges even though there is no thyroid disease present. RT3 may be elevated in non-thyroidal conditions, particularly the stress of illness. It is generally recommended that thyroid testing be avoided in hospitalized patients or deferred until after a person has recovered from an acute illness. Use of the RT3 test remains controversial, and it is not widely requested.

The Role Of Thyroid Testing

A thyroid function test will allow your healthcare provider to assess if the thyroid gland continues to function as it should be. It detects hyperthyroidism and hypothyroidism .

In addition, thyroid testing helps conditions like Graves disease, Hashimotos thyroiditis, goiter, and imbalances involving thyroid hormones. The same blood test for thyroid is also typically ordered to evaluate the effectiveness of a particular treatment for the conditions mentioned above, among others.

Thyroid tests are crucial in understanding metabolic processes and problems affecting these activities. Check out the different blood tests for thyroid function here at Personalabs. Order the one you require online and take it to one of our partner medical laboratories for accurate testing.

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Radioactive Iodine Uptake Test

A radioactive iodine uptake test, also called a thyroid uptake test, can help check thyroid function and find the cause of hyperthyroidism. The thyroid takes up iodine from the blood to make thyroid hormones, which is why this is called an uptake test. Your health care professional may ask you to avoid foods high in iodine, such as kelp, or medicines containing iodine for a week before the test.

For this test, you will swallow a small amount of radioactive iodine in liquid or capsule form. During the test, you will sit in a chair while a technician places a device called a gamma probe in front of your neck, near your thyroid gland. The probe measures how much radioactive iodine your thyroid takes up from your blood. Measurements are often taken 4 to 6 hours after you swallow the radioactive iodine and again at 24 hours. The test takes only a few minutes.

If your thyroid collects a large amount of radioactive iodine, you may have Graves disease, or one or more nodules that make too much thyroid hormone. You may have this test at the same time as a thyroid scan.

Even though the test uses a small amount of radiation and is thought to be safe, you should not have this test if you are pregnant or breastfeeding.

How Does A Blood Test For Hypothyroidism Work

Thyroid profile T3 T4 TSH test in Hindi | Thyroid function test kya hota hai?

How to test for hypothyroidism?

Itâs important to note that there is no hypothyroidism test that can check thyroid hormones andâbased only on those test resultsâconclusively determine if someone has hypothyroidism. Thatâs because both thyroid hormone testing and a physicianâs evaluation of symptoms and medical history is required for a diagnosis.

A blood test for hypothyroidism is based on your levels of thyroid-stimulating hormone and the thyroid hormones T3 and T4. Because TSH signals the thyroid gland to produce more thyroid hormones, unusually high levels of TSH can mean that your thyroid isnât making enough hormones.

A thyroid lab test might also measure T3 and T4 to reveal just how low your thyroid hormone levels are, which can help your healthcare provider decide on a treatment strategy.

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Drawing Blood For Thyroid Function Tests

Before you get a blood draw to check your thyroid levels, talk with your doctor about any medications youre taking. Also let them know if youre pregnant. Certain medications and being pregnant may influence your test results.

A blood draw, also known as venipuncture, is a procedure performed at a lab or a doctors office. When you arrive for the test, youll be asked to sit in a comfortable chair or lie down on a cot or gurney. If youre wearing long sleeves, youll be asked to roll up one sleeve or to remove your arm from the sleeve.

A healthcare professional, like a technician or nurse, will tie a band of rubber tightly around your upper arm to make the veins swell with blood. Once the healthcare professional has found an appropriate vein, theyll insert a needle under the skin and into the vein.

You may feel a sharp prick when the needle punctures your skin. The healthcare professional will collect your blood in test tubes and send it to a laboratory for analysis.

When the healthcare professional has gathered the amount of blood needed for the tests, theyll withdraw the needle and place pressure on the puncture wound until the bleeding stops. They will then place a small bandage over the wound.

You should be able to return to your typical daily activities immediately.

What Should I Take Care Of After Getting Tested For Thyroid Hormones

Once the blood sample for thyroid test is drawn, you can return to normal activities, including driving. A simple thing that you can follow is to avoid strenuous activity with the arm from where the sample was taken for a few hours after the tsh test. If you experience any pain or bleeding, apply ice packs

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How Does The Thyroid Gland Function

The major thyroid hormone secreted by the thyroid gland is thyroxine, also called T4 because it contains four iodine atoms. To exert its effects, T4 is converted to triiodothyronine 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, which is made in the pituitary gland located at the base of the brain, called thyroid stimulating hormone . The amount of TSH that the pituitary sends into the bloodstream depends on the amount of T4 that the pituitary sees. If the pituitary sees very little T4, then it produces more TSH to tell the thyroid gland to produce more T4. Once the T4 in the bloodstream goes above a certain level, the pituitarys production of TSH is shut off. In fact, the thyroid and pituitary act in many ways like a heater and a thermostat. When the heater is off and it becomes cold, the thermostat reads the temperature and turns on the heater. When the heat rises to an appropriate level, the thermostat senses this and turns off the heater. Thus, the thyroid and the pituitary, like a heater and thermostat, turn on and off. This is illustrated in the figure below.

Thyroid #4 Comprehensive Blood Test Panel

Thyroid Function Test Interpretation

The Thyroid #4 Comprehensive Blood Test Panel includes a Thyroid Profile with TSH, Tri-iodothyronine Free Serum, Thyroxine Free Direct Serum, Thyroid Peroxidase Antibodies, Thyroid Antithyroglobulin Antibody plus Reverse T3, Thyroxine-binding Globulin , Thyroid-stimulating Immunoglobulin , and Tri-iodothyronine .

CPT Code: See Individual Tests

Also Known As:

No fasting required. Stop biotin consumption at least 72 hours prior to the collection.

Test Results:

4-6 days. May take longer based on weather, holiday or lab delays.

CPT Code: See Individual Tests

Also Known As:

No fasting required. Stop biotin consumption at least 72 hours prior to the collection.

Test Results:

4-6 days. May take longer based on weather, holiday or lab delays.

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Interpreting Thyroid Function Test Results

While normal ranges may vary from lab to lab, generally each hormone should fall within a reference range that is considered normal. Acceptable ranges are:

  • TSH: 0.4-4.5 mIU/mL

Some institutions may use narrower ranges depending on how the blood is analyzed in the lab. When looking at your results, typically there is a reference range listed so you know if the measurement is normal for that specific lab.

If your results are outside the normal range, this may indicate temporary fluctuations in thyroid function rather than a longer-term thyroid condition. And day-to-day variation in levels can be normal and part of a healthy, responsive endocrine system.

What Should I Do To Prepare For A Thyroid Function Test

Thyroid function tests usually require very little preparation.

You don’t need to fast before the blood test. And it doesn’t matter if you have taken your thyroid medicine just before the blood test.

Tell your doctor if you are taking any medication, as some medicines can alter the test results and how they are interpreted.

It is also important to mention if you have had any X-ray tests that have used a special contrast dye, as this may contain iodine which can affect the results. Levels of thyroid chemicals also change in pregnancy, so tell your doctor if you are pregnant when the test is taken.

Note: all newborn children have their thyroid function tested as part of the heel prick test which is offered to all babies and undertaken when they are 5 days old. See the separate leaflet called Newborn Baby Screening Tests for more information.

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