Thyroid Testing: What Labs Do I Need?

Thyroid Testing

The thyroid gland is a butterfly shaped gland located near the front of your throat.

It’s part of the endocrine system and produces hormones that help our bodies utilize energy, and contribute to heart, brain, and bone health. A helpful metaphor when thinking about the thyroid gland is a heating system in a house.

The thyroid gland is the furnace, the hormones T3 and T4 are the heat produced, and the pituitary gland in the brain is the thermostat using TSH to increase or decrease the heat in the house. 

Thyroid Testing

Most doctors recommend testing adult thyroid function annually, and will order further testing if needed.

Thyroid function is also very important in pregnancy and doctors will usually test early on. A low functioning thyroid (hypothyroidism) often manifests as low energy and weight gain. A higher-than-normal functioning thyroid (hyperthyroidism) shows up as unexplained weight loss, racing heart, insomnia, and sweating. Low thyroid is much more common. 

What are the various kinds of labs that are usually looked at when testing for thyroid health?

Often people are getting TSH (Thyroid Stimulating Hormone) tested, but there are many others as well: T3, T4, Free T3, Free T4, TPO, and TgAb to name a few. 

TSH – Thyroid Stimulating Hormone

This hormone is produced by the pituitary gland in the brain and it acts to stimulate the thyroid gland. Generally speaking, if the thyroid gland isn’t working very well, then the TSH would be high. In a sense, the brain ‘yelling’ at the thyroid gland to work better. Low TSH could indicate hyperthyroidism. 

T3 – Triiodothyronine

The thyroid gland itself produces two hormones: T3 (Triiodothyronine) and T4 (Tetraiodothyronine, also known as thyroxine). T3 is the active thyroid hormone, helping all over the body in areas like heart function, stimulating the intestines, cholesterol management, and bone maintenance to name a few.

The thyroid gland only releases a small amount of T3 as compared to T4. Most of the T3 is converted from T4 after it’s been released by the thyroid. A lot of T3 (coming back high on a test) would indicate the thyroid is making too much and low T3 could indicate the thyroid isn’t making enough, or enough isn’t being converted from T4. 

T4 – Tetraiodothyronine/Thyroxine

T4 is the other hormone produced by the thyroid gland. It is inactive when released by the thyroid and gets converted in the body by the liver and kidneys into active T3. 

Free T3 and Free T4

Free thyroid hormones are not bound to proteins so can be used by the body where they are needed (heart, lungs, bones, many neurotransmitter receptors, etc). Knowing the “free” numbers can be helpful to understand what the body can utilize or if everything produced is being rendered unusable through being bound in a protein. 

TPO (Thyroid peroxidase) antibody test.

Thyroid peroxidase is an enzyme normally found in the thyroid, so testing for an antibody (immune system alert) against the TPO is part of understanding if the immune system is attacking the thyroid gland. Immune system attacks such as Hashimoto’s disease or Grave’s disease are sometimes causes of a dysfunctioning thyroid gland. 

TgAb – Thyroglobulin antibody.

Thyroglobulin is a protein produced by the thyroid gland, so this is a test to see if the immune system is attacking the protein by producing an antibody against it. If there is a high antibody it would indicate an autoimmune disease like Hashimoto’s. 

Ready to take control of your thyroid health?

Don’t settle for incomplete testing approaches that may not effectively address your concerns. Our team of naturopathic doctors are experts in thyroid evaluation and management and can provide personalized care to support your unique needs.

Schedule an appointment today and let us help you on your journey towards optimal thyroid function.

Feel free to schedule a consultation with the providers at Naturopathic Family Health if you have any specific concerns.  

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Dr. Jennifer Potter ND

Dr. Jennifer Potter, ND
Naturopathic Doctor San Jose


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