Thyroid test
Checking thyroid function depends on various factors. But if you have hypothyroidism or hyperthyroidism, you should test your thyroid regularly. The thyroid is located in the front of the neck and produces the following three hormones:
- T3 (triiodothyronine)
- T4 (tetraiothyronine)
- Calcitonin
T3 and T4 are the active forms of the thyroid hormone thyroxine and play a role in regulating the following:
- The rate of body metabolism
- Heart function
- Digestive function
- Muscle control
- Brain development
- Bone maintenance
Why is testing important?
If left untreated, hypothyroidism can lead to other complications such as goiter, heart problems, mental health problems, peripheral neuropathy, myxedema, infertility and birth defects. Only through tests can this disorder be diagnosed early to prevent other complications and identify possible causes that can be serious.
Early detection and treatment of hyperthyroidism can help prevent complications from conditions such as Graves’ disease, which worsen over time and are associated with a higher risk of death. Hyperthyroidism can also lead to atrial fibrillation (a common and dangerous type of heart arrhythmia, or irregular heartbeat that cuts off blood flow and may lead to stroke) and congestive heart failure.
Observing what symptoms should a thyroid test be done?
Additionally, certain people are at risk for hypothyroidism and should talk to their doctor about a TSH blood test. A TSH blood test shows whether you have a normal TSH level. Talk to your doctor about your thyroid if you have:
- An autoimmune disease (such as type 1 diabetes)
Pernicious anemia (low red blood cells)
- Parents or siblings with autoimmune thyroid disease
- Neck radiation therapy to treat hyperthyroidism or to treat head or neck cancer
- Thyroid surgery or thyroid problem (thyroid dysfunction)
- Abnormal thyroid
A mental health problem (eg, depression)
- If you are taking amiodarone or lithium
What is measured in a thyroid test?
The three main hormones measured in the thyroid blood test are:
- Thyroid stimulating hormone (TSH)
Thyroxine (T4)
- Triiodothyronine (T3)
TSH is the most sensitive biomarker for thyroid function and is often used to make sure that the hormone replacement therapy you are prescribed is working as well as it should.
High levels of T3 and T4 often indicate hyperthyroidism, and low levels indicate hypothyroidism.
Thyroid problems can be detected by measuring the level of free T3 (FT3) in the blood. High levels indicate hyperthyroidism and low levels indicate hypothyroidism.
T3 can be used to:
- The test shows whether the thyroid is working properly
- Diagnosis of hyperthyroidism (hyperthyroidism)
- T3 is only requested when diagnosing or testing the severity of hyperthyroidism.
T4 levels are often used along with presenting symptoms to identify a thyroid problem.
There are two additional biomarkers that can be added to thyroid testing:
- Thyroglobulin antibodies
- Thyroid peroxidase antibodies
Thyroglobulin is a protein stored in the thyroid gland that helps produce T3 and T4. Thyroid peroxidase antibodies help identify autoimmune thyroid disease.
What are the symptoms of hyperthyroidism?
An overactive thyroid is a condition in which the thyroid is overactive and produces too much thyroid hormone.
When T3 and T4 hormones are produced in excess, the following symptoms may occur:
- Feeling nervous, anxious, or irritable
- Weight Loss
- High activity
- Mood swings
- Diarrhea
- Fatigue
- Muscle weakness
- Itching
- Low libido
- The need to pass more urine
- Increased thirst
What are the symptoms of hypothyroidism?
On the other hand, hypothyroidism is characterized by decreased thyroid activity in the sufficient production of T3 or T4 hormones. As a result, symptoms can include:
- Fatigue
- Feeling cold
- Depression
- Weight Gain
- Muscle cramps and pain
- Low libido
- Brittle hair and nails
- dry skin
- Irregular or heavy periods
What is the normal range for a thyroid test?
Laboratories use reference ranges when analyzing thyroid function. A typical reference range for an individual is usually as follows:
- TSH 0.27-4.2 mIU/L
- FT4 12.0 – 22.0 pmol/L
- FT3 3.1 – 6.8 pmol/L
Different laboratories use different reference ranges, but if your results fall outside these parameters, you may be diagnosed with hypothyroidism or hyperthyroidism.
On the other hand, subclinical hypothyroidism occurs when your blood TSH level is slightly elevated but your FT4 is in the normal range.
When is the hypothyroidism and hyperthyroidism test done?
If you have an underactive thyroid, you should have your thyroid-stimulating hormone (TSH) level tested once a year to make sure it’s within normal parameters.
If your thyroid is overactive, your doctor may want to test your TSH and FT4 levels monthly to see how your treatment is progressing, and then test less frequently. However, you will be told the number of tests after the diagnosis and depending on the treatment.
Experts recommend that adults should be screened for thyroid disease starting at age 35 and every 5 years thereafter.
How is the thyroid test done?
A series of blood tests called thyroid function tests are done to measure T3, T4, and TSH (thyroid-stimulating hormone secreted by the pituitary gland) and T3RU (T3 resin uptake). T4 and TSH tests are usually done together and are very common.
If the T4 level is high, a thyroxine (T4) test indicates hyperthyroidism. It measures the amount of free T4 (not bound to protein) in the blood. The normal range is from 9.0 to 25.0 pmol/l (picomole per liter).
Thyroid-stimulating hormone (TSH) level test indicates hyperthyroidism if the level is abnormally low. Relatively low levels indicate normal thyroid hormone levels. The normal range is between 0.4 and 4.0 mIU/l (milli international units of hormone per liter of blood). If the value is above 2.0 mIU/l, there is a risk of hypothyroidism.
If these two tests indicate hyperthyroidism, a T3 test is performed. The normal range is 100 to 200 ng/dL. Any value higher than this is considered abnormally high and is most likely a sign of Graves’ disease.
Cholesterol and triglyceride levels are also tested to indicate increased metabolic rate.
If the blood test shows a functional imbalance in the thyroid gland, an ultrasound test is recommended to check for structural problems of the gland, gland activity and tumors.
These conditions are treated with the help of drugs that stop or stimulate the activities of the thyroid gland. Surgery and radioactive iodine are also used to treat hyperthyroidism. A proper diet can prevent these disorders.
A TSH test is done once a year in case of hypothyroidism to check if the level is within the normal range. The frequency of hyperthyroidism tests (usually TSH and T4) depends on the treatment. In any case, initially, blood tests are taken once every few weeks, and as the treatment stabilizes, its frequency decreases.
References
https://www.thyroidsymptoms.ca/en-ca/hypothyroidism-faqs/how-often-should-i-be-tested-for-thyroid-disease#:~:text=Experts%20recommend%20that%20adults%20be,about%20a%20TSH%20blood%20test.
https://www.forthwithlife.co.uk/blog/how-often-should-a-thyroid-test-be-carried-out/
https://www.apollodiagnostics.in/blog/how-often-should-you-get-a-thyroid-blood-test
