Important thyroid function tests you should be aware of

Thyroid disease comes in many forms. Most thyroid disorders, including hypothyroidism and hyperthyroidism, have non-specific symptoms that can be difficult to diagnose.

Unexplained weight gain or weight loss, fatigue, and depression are among the most common signs of thyroid dysfunction. However, these symptoms may also indicate less serious conditions.

If you have a family history of thyroid disease, get some blood tests done. The same goes for those who are over the age of 60, had their thyroid gland removed, or received treatment with radioactive iodine. Pregnant women and people who take immunosuppressants are at risk too. So, here are the most important thyroid function tests you should be aware of:

TSH Test

Abnormal TSH (thyroid-stimulating hormone) levels are an indicator of thyroid disease. If your TSH levels too high, it means you have an underactive thyroid. Low TSH levels usually show that the person has an overactive thyroid, which may progress to hyperthyroidism.

According to health experts, TSH is the gold standard for thyroid disease diagnosis. However, this test alone doesn’t provide a complete picture. Many people experience adrenal fatigue and other signs of thyroid dysfunction despite having their TSH levels within normal limits. Additionally, TSH lab ranges are controversial. Sometimes, low TSH levels may result from a dysfunction of the pituitary gland.

To get rid of doubt, request a full thyroid blood panel.

T4 Test

The T4 (thyroxin) test helps diagnose hypothyroidism. T4 levels that are below normal indicate an underactive thyroid. The normal limits range from 5 to 13.5 micrograms per deciliter. However, these numbers vary from one lab to another.

T3 Test

Your health care provider might recommend the T3 (triiodothyronine) to diagnose hyperthyroidism. The normal limits are between 100 and 200 nanograms per deciliter. If your T3 levels are too high, you might suffer from Grave’s disease or overactive thyroid.


T3RU also referred as T3 resin uptake measures the levels of thyroxin-binding globulin (TBG) in your bloodstream. If its levels are too high, you might have protein deficiency or kidney problems. Abnormally low TBG levels indicate excess estrogen production, which may be caused by hormone replacement therapy, obesity, or a diet rich in estrogen-forming foods, such as soy, legumes, and sugar.

Tg Test

This test shows how much thyroglobulin (Tg) is in your system. Thyroglobulin is a protein produced by thyroid cells. In general, the Tg test is recommended to people who had their thyroid removed after a cancer diagnosis and helps determine thyroid function.

TSI Test

The TSI (thyroid-stimulating immunoglobulin) test indicates whether or not you have recovered from hyperthyroidism. It also measures the levels of TSI, an autoantibody present in Graves’ disease.

Be aware that none of these tests is 100 percent accurate. Lab errors, subtle hormonal imbalances, outdated TSH lab ranges, and thyroid hormone resistance can affect your results. This means that your test results can be normal even if you have thyroid disease. In case you still experience symptoms, get tested again or request a more in-depth examination. Consider switching your doctor and/or lab if necessary.

You know your body better than anyone – if something doesn’t feel right get second, third and fourth opinions if necessary. You need to be your own advocate and always trust your instincts.