Thyroid Test: What is It and Why is It Important?

To accurately diagnose thyroid disorders and understand how your body’s thyroid hormones work, thyroid testing is essential. Blood tests to measure thyroid hormones are readily available and widely used, but not all are useful in all situations. Therefore, you might need special tests to evaluate thyroid function.

This article discusses thyroid testing fundamentals and explains the options available for you.

The Importance of Thyroid Testing

The butterfly-shaped thyroid is the endocrine gland responsible for making calcitonin, thyroxine (T4) and triiodothyronine (T3). Research suggests that only T3 and T4 are proper thyroid hormones produced by the thyroid gland. An imbalance in these hormones leads to many symptoms. For instance, a chemical or hormonal imbalance arises when the thyroid gland makes too many hormones or doesn’t make enough hormones.

Thyroid dysfunction symptoms are exceedingly common but are non-specific, making it difficult to self-diagnose. Therefore, healthcare professionals rely on biochemical testing to confirm the presence of any possible thyroid disorder. 

Thyroid tests can aid in diagnosing thyroid conditions such as goitre, thyroiditis, and thyroid cancer and help your doctor better understand your situation. Measuring thyroid antibodies level helps diagnose an autoimmune thyroid disorder like Graves’ disease. It is the most common cause of Hashimoto’s disease and hyperthyroidism. In addition, thyroid tests can help you identify congenital hypothyroidism in newborns. 

Thyroid Function Tests

Blood tests called thyroid function tests can detect a hyperactive or underactive thyroid gland. It can also provide information about other disorders that are related to it. The most common tests for thyroid function are:

Thyroid-stimulating Hormone (TSH) Test

The pituitary gland in the brain produces a hormone called TSH, or thyroid-stimulating hormone. The pituitary gland produces more TSH when the thyroid levels in your body fall.

The TSH tells the thyroid gland to adjust by releasing more thyroid hormones. Conversely, the pituitary gland produces less TSH when the thyroid hormone level is high. Therefore, excessively high or low TSH readings can indicate whether your thyroid is functioning correctly. 

A high TSH level indicates that the thyroid gland is underactive and not making enough thyroid hormone. The opposite situation is when the TSH level is low, meaning the thyroid produces too much thyroid hormone or is overactive. A normal TSH value test result means that the thyroid is functioning correctly.

T4 Test

A Total T4 test measures the blood level (bound and free level) of the hormone T4. A Free T4 test measures how much hormone is not bound and is free to enter and affect the body tissues.

It is good practice for doctors to measure T4 in children, as T4 is essential to brain development. Tests measuring free T4 hormone more accurately reflect how the thyroid gland functions when checked with a TSH.

Results showing an elevated TSH but low free T4 (FT4) indicate primary hypothyroidism caused by any disease in the thyroid gland. On the other hand, low TSH and FT4 values indicate hypothyroidism due to a pituitary gland problem. A low TSH with an elevated FT4 signifies the presence of hyperthyroidism.

T3 Test

T3 test measures the other major thyroid hormone, T3 (triiodothyronine), in the blood. It is helpful to diagnose hyperthyroidism and determine the severity of your hyperthyroidism. It is because people who are hyperthyroid shows an elevated T3 level. However, T3 testing is rarely helpful in hypothyroid patients because they can have a normal T3 with a high TSH and low FT4.

Thyroid Antibodies Test

Thyroid antibodies are produced by the immune system, causing an autoimmune thyroid condition that results when these cells target and kill healthy thyroid cells.

While specific antibodies damage thyroid tissue and cause low thyroid hormone levels, other antibodies induce the thyroid to release excessive thyroid hormones. 

You can detect thyroid antibodies with a thyroid antibodies test. Thyroid peroxidase, thyroglobulin, and thyroid-stimulating hormone receptor antibodies are the most well-known thyroid antibodies.

The HealthifyMe Note

When the thyroid generates either excessive or insufficient hormones, it poses a significant health risk. Therefore, thyroid tests are essential to understand how your body is doing regarding its thyroid hormone levels and antibodies. While thyroid hormone levels can be determined by blood tests known as thyroid function tests, thyroid antibody tests detect different types of thyroid antibodies that cause autoimmune diseases. 

When Do You Need to Get Tested?

Testing is when you experience thyroid-related symptoms, or your doctor has suspicions about an autoimmune thyroid disorder. Losing weight, anxiety, anger, sadness, hair loss, and missed or light periods are all indications of hyperthyroidism, which cause high T3 and T4 levels.

Lethargy, difficulty concentrating, weight gain, melancholy, excessive menstrual bleeding, and joint and muscular pain are all common signs of hypothyroidism (low T3 and T4 levels).

Normal Reference Range

For any abnormal value, you should consult a doctor. According to the results of your thyroid test, your hormone levels should typically fall between the following range:

• T3: 100–200 nanograms per deciliter of blood (ng/dL)
• T4: 4.5 – 11.2 micrograms per deciliter of blood (mcg/dL)
• TSH: 0.4 – 5.0 milli-international units per litre (mIU/dL)
• TSH (If you already have thyroid): 0.5-0.3 milli-international units per litre (mIU/dL)

Preparation Tips and Precautions

• Typically, no additional precautions, such as fasting, are required before a thyroid test.
• Take your blood test before taking your daily dose if you are already on medication for thyroid illness.
• You can take a thyroid test when pregnant if necessary because thyroid alterations are frequent during this time.
• As consuming biotin (Vitamin B7) two days before a thyroid function test is known to cause some aberrancy in your test results, it is best to avoid taking it.

Conclusion

The primary aim of thyroid tests is to diagnose thyroid disorders in the early stages. Testing is vital since it is the most accurate method for diagnosing and treating thyroid problems. In addition, the test results can help your doctor develop an effective diagnosis and treatment plan. Talk to your doctor if you have questions or concerns about your thyroid tests.