Reading Other Thyroid Test Results
Why Would I Need These Tests
The thyroid gland‘s hormones help control some of your body’s metabolic processes, such as heart rate, blood pressure, body temperature and weight. Too much or too little of these hormones can make you ill.
You might need thyroid tests if:
- you have symptoms of hyperthyroidism or hypothyroidism
- you are taking some form of thyroid hormone replacement treatment
- you are female and being investigated for infertility
Very rarely, babies are born without a working thyroid gland. For this reason, all Australian newborns are screened for hypothyroidism with a TSH test using a drop of blood taken from a heel prick.
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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Signs You Should Do A Thyroid Function Test
If any of these hormones are out of balance it can lead to a thyroid disorder and cause a wide range of symptoms. If youre experiencing any of these symptoms its really important to check your thyroid function. Its also common for thyroid disorders to run in families so its particularly important to test your thyroid function if you think you might be at risk. You can test your thyroid function as part of our women’s hormones blood test.
Magnetic Resonance Imaging Scan
MRI scans use magnets instead of radiation to create detailed cross-sectional images of your body. MRI can be used to look for cancer in the thyroid, or cancer that has spread to nearby or distant parts of the body. But ultrasound is usually the first choice for looking at the thyroid. MRI can provide very detailed images of soft tissues such as the thyroid gland. MRI scans are also very helpful in looking at the brain and spinal cord.
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Illness And Thyroid Test Results
Certain illnesses can temporarily affect thyroid hormone results. Diarrhea can interfere with your medication absorption and may alter your lab results. Infections or a bout of an inflammatory condition such as lupus can also have an effect.
A syndrome called nonthyroidal illness or sick euthyroid syndrome can also affect thyroid function and test results. This is a serious illness that requires hospitalization.
People with this condition have a normal TSH level with a low T4 and T3 level. These changes in thyroid levels are thought to be protective. For that reason, people with this condition do not receive treatment to correct thyroid levels.
T3 Resin Uptake Results
A T3 resin uptake, also known as a T3RU, is a blood test that measures the binding capacity of a hormone called thyroxin-binding globulin . If your T3 level is elevated, your TBG binding capacity should be low.
Abnormally low levels of TBG often indicate a problem with the kidneys or with the body not getting enough protein. Abnormally high levels of TBG suggest high levels of estrogen in the body. High estrogen levels may be caused by pregnancy, eating estrogen-rich foods, obesity, or hormone replacement therapy.
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What Are Thyroid Blood Tests
Doctors use blood tests to check for thyroid or pituitary problems. In kids already diagnosed with thyroid or pituitary problems, the tests are used to guide treatment.
Commonly ordered thyroid blood tests include:
- T4 test: This is done to measure the blood level of the hormone T4 . It might be done in one or both of the following ways:
- total T4, which measures the entire amount of thyroxine in the blood, including the amount attached to blood proteins that help carry the hormone through the bloodstream
- free T4, which measures only the thyroxine that’s not attached to proteins. This is the part of T4 in the blood that affects how the body’s cells work.The results of the T4 blood tests can help diagnose hyperthyroidism or hypothyroidism and guide treatment.
In some cases, abnormal thyroid test results can be due to a medicine, an ongoing medical condition, or pregnancy. In these cases, there may be nothing wrong with the thyroid or pituitary glands themselves.
What Is A Thyroid
Your thyroid is a small gland found at the front of your windpipe . It produces two hormones that help control your metabolism the chemical processes that occur in your body that keep you alive, like breathing and breaking down food into energy. These hormones are called triiodothyronine and thyroxine .
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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.
What Blood Tests Are Done To Test The Thyroid
Thyroid blood tests include:
These tests alone arent meant to diagnose any illness but may prompt your healthcare provider to do additional testing to evaluate for a possible thyroid disorder.
Additional blood tests might include:
- Thyroid antibodies: These tests help identify different types of autoimmune thyroid conditions. Common thyroid antibody tests include microsomal antibodies , thyroglobulin antibodies , and thyroid receptor antibodies .
- Calcitonin: This test is used to diagnose C-cell hyperplasia and medullary thyroid cancer, both of which are rare thyroid disorders.
- Thyroglobulin: This test is used to diagnose thyroiditis and to monitor treatment of thyroid cancer.
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Are There Any Specific Tests For Hypothyroidism
Thyroxine is the primary hormone produced by the thyroid gland in response to stimulation by the pituitary gland.
A ‘feedback system’ exists between the thyroid gland and the pituitary gland. When T4 concentrations in the blood are low, the pituitary sends a signal to the thyroid gland using thyroid stimulating hormone , prompting the thyroid gland to produce more T4. When T4 levels in the circulation are adequate, the pituitary decreases its production of TSH, thereby reducing the production of T4.
“If the total T4 concentration is well within the normal range, then your dog is not hypothyroid.”
Total T4 . T4 circulates in the blood in two forms one form of the hormone is bound, or attached to proteins in the blood, while the other form circulates freely within the blood stream. Total T4 measures both forms of the hormone in a blood sample. If the total T4 concentration is well within the normal range, then your dog is not hypothyroid. If the total T4 concentration is at the low end or below the normal range, and your dog has supportive clinical signs, then hypothyroidism is likely. Unfortunately, there are conditions other than hypothyroidism that may cause the total T4 value to be reduced. These conditions include the presence of another illness or the administration of some drugs, such as anti-inflammatory medications. Your veterinarian may be able to measure total T4 levels in the veterinary office.
Fasting And Thyroid Test Results
Studies have shown that time of day and fasting can affect your results. If you test in the early morning after overnight fasting, the results may show higher levels. This is compared to tests done later in the day with no fasting.
This condition is diagnosed and monitored based solely on TSH. T4 and T3 levels are usually normal.
If you get your blood test in the afternoon when you have not been fasting, your TSH levels will be lower. Because of this, your subclinical hypothyroidism may be missed.
Low Ft4 With Inappropriately Normal Or Low Tsh
This combination of TFTs is also seen in NTI and resolves with recovery. However, in the absence of a clear alternative diagnosis, central hypothyroidism must be considered and a full pituitary hormone profile, including assessment for secondary hypoadrenalism, is mandatory. T4 therapy in patients with untreated hypocortisolism can be life threatening and failure to recognise a large pituitary mass compressing the optic chiasm can result in irreversible visual loss.
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Who Is This Test For
People who may benefit from having a thyroid function test include:
Individuals who are concerned that they may have a thyroid problem and those who wish to monitor a previously diagnosed condition.
Early signs and symptoms of thyroid dysfunction may often be very non-specific. The common symptoms hypothyroidism may include:
- Unexplained weight gain
- Bulging, dry, puffy or irritated eyes
- Difficulty sleeping
What will the result show?
Our thyroid test will report your levels for all three hormones . You will receive a personalised interpretation of what the results mean and what you should do about them. This may be as simple as all is well, to a recommendation to see your GP if we detect an abnormality.
In hypothyroidism, the thyroid gland does not produce sufficient thyroxine, so the T4 and T3 levels are low.
This causes an increase in TSH to try and stimulate the thyroid to produce more thyroxine.
In hyperthyroidism the thyroid gland produces too much thyroxine, so the T4 levels are high. This causes a decrease in TSH to try and stop the thyroid producing more thyroxine.
“I use MMH to keep an eye on my thyroid levels and as it’s an NHS lab, my GP and endocrinologist can use the results to monitor me. I was grateful for having the option of home testing last year, when I was unable to get to my surgery due to ill health. Very quick service and I like the graphs showing my health journey.”
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What Is A Normal Thyroid Level
Tests often used to assess thyroid hormone status include TSH and FT4 tests. The normal value for a laboratory test is determined by measuring the hormone in a large population of healthy individuals and finding the normal reference range. Normal ranges for thyroid tests may vary slightly among different laboratories, and typical ranges for common tests are given below.
TSH normal values are 0.5 to 5.0 mIU/L. Pregnancy, a history of thyroid cancer, history of pituitary gland disease, and older age are some situations when TSH is optimally maintained in different range as guided by an endocrinologist.
FT4 normal values are 0.7 to 1.9ng/dL. Individuals taking medications that modify thyroid hormone metabolism and those with a history of thyroid cancer or pituitary disease may be optimally managed with a different normal FT4 range.
Total T4 and Total T3 levels measure bound and free thyroid hormone in the blood. These levels are influenced by many factors that affect protein levels in the body, including medications, sex hormones, and liver disease. A normal Total T4 level in adults ranges from 5.0 to 12.0g/dL. A normal Total T3 level in adults ranges from 80-220 ng/dL.
Free T3 assays are often unreliable and not routinely used to assess thyroid function.
What Are The Types Of Thyroid Disorders
Blood tests are used to diagnose hypothyroidism or hyperthyroidism. They do not point to a specific cause. In order to determine a cause of the thyroid abnormality, the doctor will consider the patient’s history, physical examination, and medical condition. Further testing might be used to isolate an underlying cause. These tests might include more blood testing for
- thyroid antibodies,
- ultrasound of the thyroid gland, or
If thyroid cancer is suspected and surgery may be required, your physician may ask for a blood test known as thyroglobulin.
- Thyroglobulin is a protein made only by thyroid cells.
- If the thyroglobulin level at baseline is detectable or elevated it can be used as a tumor marker.
- After a total thyroidectomy for cancer the level should fall to an undetectable range since the cells that make thyroglobulin have been removed.
- If the level remains detectable after surgery, there is a possibility of thyroid tissue elsewhere in the body, and metastatic disease should be considered.
- If the level is undetectable for a period of time after surgery and then starts to climb, a recurrence of the cancer – either at the primary site or elsewhere in the body should be considered.
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How To Keep Hypothyroidism Under Control
Because youll need to take thyroid medication every day for the rest of your life, even after the right dose is found, your hormone levels will be monitored regularly to be sure that your treatment is working properly. Eventually, most people with hypothyroidism can just be seen yearly by their doctor, Doria-Medina says.
The American Thyroid Association recommends that you keep your TSH within a narrow range of 0.5 to 2.5 mU/L, but dont be alarmed if your test results vary a little. Some variation is normal because your pituitary gland sends out TSH in pulses, not a steady stream. Also, factors like the time of day youre tested can make a difference. TSH levels are likely to be higher at night and lower during the day. Some people, including those who are pregnant or those with a history of thyroid cancer, have different TSH goals. Talk to your doctor about the target TSH range thats right for you.
If you have new or worsening symptoms or your health status changes such as if you become pregnant, go through menopause, or are given another medicine that can interfere with the absorption of your thyroid hormones, such as anticonvulsants, certain antacids, or iron or calcium supplements you should see your doctor and have your blood tested again, even if its ahead of schedule.
How To Check Your Thyroid
This article was medically reviewed by Ricardo Correa, MD. Dr. Correa is a board certified Endocrinologist. Dr. Correa is the Program Director of the Endocrinology, Diabetes and Metabolism Fellowship at the University of Arizona College of Medicine and was a previous Assistant Professor of Medicine at Brown University. He completed his MD at the University of Panama and completed an internal medicine residency at the Jackson Memorial Hospital – University of Miami. He has been voted one of the 40 Under 40 Leaders in Health by the National Minority Quality Forum in 2019.There are 12 references cited in this article, which can be found at the bottom of the page. This article has been viewed 43,961 times.
The thyroid gland is located at the base of your neck. It is a very important gland that produces a hormone that helps regulate your entire bodys metabolism, temperature, heart rate, growth, and development.XResearch source The thyroid gland can be functionally underactive or overactive. The thyroid can be enlarged, have benign nodules and, more rarely, malignant nodules.
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