Testing for Thyroid Imbalances
As mentioned in our previous blog, several different tests can be done to diagnose a thyroid imbalance.
The thyroid hormones your body creates are called Thyroxine (T4) and triiodothyronine (T3). The thyroid-stimulating hormone (TSH) functions to release these two hormones. In this post, we go over how each lab test works and which might be the most effective for you.
TSH Test
Testing for TSH is a great initial step because changes in TSH levels in the blood can be an early warning sign before the actual thyroid hormone levels become out of balance. When levels are low, this can indicate hyperthyroidism. When levels are high, this is a sign of hypothyroidism.
T4 Test
T4 is the main thyroid hormone in the blood. This test can measure the total bound and free hormone level. More commonly, doctors look for Free T4 (FT4), which measures what is not able to enter the body tissues. When FT4 is low and TSH levels are high, this is a sign of hypothyroidism. When FT4 is elevated and TSH levels are lower this a sign of hyperthyroidism.
T3 Test
T3 is another major hormone produced by the thyroid. This test is only accurate when testing for hyperthyroidism, not hypothyroidism. Those with an elevated T3 level will be diagnosed with hyperthyroidism. 1
Reverse T3
This test measures the inactive form of the hormone T3 and is not a common lab test. Reverse T3 (RT3) is relevant to consider, but it usually can not provide a clear diagnosis. People who have hypothyroidism may have low RT3, but the change doesn’t always occur. 2
Thyroid antibody test
Doctors test for the antibodies known as thyroid peroxidase and thyroglobulin to diagnose the cause of a thyroid problem. Commonly, a positive antibody test in a patient with hypothyroidism results in a diagnosis of Hashimoto’s thyroiditis. Hashimoto’s, an autoimmune disorder, is the most common cause of hypothyroidism. Hashimoto’s causes the immune system to make antibodies that attack the thyroid gland. This disease can take years to progress but starts off with swelling of the throat and then has the same signs and symptoms as hypothyroidism. 3
1 American Thyroid Association. (2020, June 8). Thyroid Function Tests. https://www.thyroid.org/thyroid-function-tests/
2 What To Expect If You Have High Reverse T3. (2020, March 28). Verywell Health. https://www.verywellhealth.com/reverse-t3-thyroid-hormone-overview-3233184#possible-significance
3 Hashimoto’s disease - Symptoms and causes. (2020, February 11). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/hashimotos-disease/symptoms-causes/syc-20351855