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 may need special tests to assess thyroid function.
This article discusses the basics of thyroid testing and explains the options available to you.
The importance of thyroid tests
The butterfly-shaped thyroid is the endocrine gland responsible for making calcitonin, thyroxine (T4), and triiodothyronine (T3). To research suggests that only T3 and T4 are proper thyroid hormones produced by the thyroid gland. An imbalance of these hormones leads to many symptoms. For example, a chemical or hormonal imbalance occurs when the thyroid gland produces too many hormones or does not produce enough hormones.
Symptoms of thyroid dysfunction are extremely common but are nonspecific, making self-diagnosis difficult. Therefore, medical professionals rely on biochemical tests to confirm the presence of any possible thyroid disorder.
Thyroid tests can help diagnose thyroid conditions such as goiter, thyroiditis, and thyroid cancer and help your doctor better understand your situation. Measuring the level of thyroid antibodies 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 hypothyroidism in newborns.
Thyroid function tests
Blood tests called thyroid function tests can detect an overactive or underactive thyroid gland. It can also provide information about other disorders 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 produces more TSH when thyroid levels in your body drop.
TSH tells the thyroid gland to adapt by releasing more thyroid hormones. Conversely, the pituitary produces less TSH when thyroid hormone levels are high. Therefore, excessively high or low TSH readings can indicate whether your thyroid is functioning properly.
A high level of TSH indicates that the thyroid gland is underactive and not producing enough thyroid hormones. The opposite situation is when the TSH level is low, which means that the thyroid is producing too much thyroid hormone or is overactive. A normal TSH value test result means that the thyroid is functioning properly.
A total T4 test measures the blood level (bound and free level) of the T4 hormone. A Free T4 test measures how much of the hormone is unbound and free to enter and affect body tissues.
It is recommended that doctors measure T4 in children because T4 is essential for brain development. Tests measuring free T4 hormone more accurately reflect the functioning of the thyroid gland when monitored with a TSH.
Results showing high TSH but low free T4 (FT4) indicate primary hypothyroidism caused by any disease of the thyroid gland. On the other hand, low TSH and FT4 values indicate hypothyroidism due to pituitary gland problem. A low TSH with a high FT4 means the presence of hyperthyroidism.
The T3 test measures the other major thyroid hormone, T3 (triiodothyronine), in the blood. Diagnosing hyperthyroidism and determining the severity of your hyperthyroidism is helpful. This is because people with hyperthyroidism have high levels of T3. However, T3 testing is rarely useful in hypothyroid patients because they may have normal T3 with high TSH and low FT4.
Thyroid antibody test
Thyroid antibodies are produced by the immune system, causing autoimmune thyroid disease which occurs when these cells target and kill healthy thyroid cells.
While specific antibodies damage thyroid tissue and cause low levels of thyroid hormone, other antibodies prompt the thyroid to release excessive thyroid hormone.
You can detect thyroid antibodies with a thyroid antibody test. Thyroid peroxidase, thyroglobulin, and anti-thyroid stimulating hormone receptor antibodies are the best known thyroid antibodies.
Note from The Fitness Freak
When the thyroid generates excessive or insufficient hormones, it poses a significant health risk. Therefore, thyroid tests are essential to understand how your body is doing with regards to its thyroid hormone levels and antibodies. While thyroid hormone levels can be determined by blood tests called thyroid function tests, thyroid antibody tests detect different types of thyroid antibodies that cause autoimmune diseases.
When do you need to get tested?
The test takes place when you experience thyroid-related symptoms or your doctor suspects an autoimmune thyroid disorder. Weight loss, anxiety, anger, sadness, hair loss, and missed or light periods are all indications of hyperthyroidism, which causes high levels of T3 and T4.
Lethargy, difficulty concentrating, weight gain, melancholy, excessive menstrual bleeding, and joint and muscle pain are all common signs of hypothyroidism (low levels of T3 and T4).
Normal reference range
For any abnormal values, you should consult a doctor. Based on your thyroid test results, your hormone levels should generally fall within the following range:
- T3: 100–200 nanograms per deciliter of blood (ng/dL)
- T4: 4.5 to 11.2 micrograms per deciliter of blood (mcg/dL)
- TSH: 0.4 to 5.0 milli-international units per liter (mIU/dL)
- TSH (if you already have thyroid): 0.5-0.3 milli-international units per liter (mIU/dL)
Preparation tips and precautions
- Generally, 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 taking medication for thyroid disease.
- You can do a thyroid test during pregnancy if necessary because thyroid alterations are common during this period.
- As consuming biotin (vitamin B7) two days before a thyroid function test is known to cause abnormalities in your test results, it is best to avoid taking it.
The main purpose of thyroid testing is to diagnose thyroid disorders at an early stage. Testing is essential as it is the most accurate method for diagnosing and treating thyroid problems. Additionally, test results can help your doctor develop an effective diagnosis and treatment plan. Talk to your doctor if you have any questions or concerns about your thyroid tests.