Last week I had a patient come in with a story that I hear way too often. She had recently been to her family doc for a number of concerns including fatigue, weight gain, and constipation. She has a history of hypothyroidism and so had some blood work done to test her hormone levels. However, when her blood work came back everything was reported as normal. Understandably, she was both frustrated and confused about what was going on in her body. Sound familiar?
If you’re convinced your thyroid isn’t functioning properly but all your lab work comes back “normal”, you might not be getting the whole picture! These are the thyroid tests you need to fully assess thyroid function.
TSH (Thyroid Stimulating Hormone)
What it is: TSH is the most common hormone that is tested to assess thyroid function. Often this is the only test done which is just not sufficient, especially if you are experiencing symptoms of low thyroid function.
What it does: TSH is produced by the pituitary gland in the brain and tells our thyroid to secrete more thyroid hormones (T4 and T3)
Why it’s important: TSH is a general measure of thyroid function. NDs like to see this value in a very narrow range, from about 1.0-2.0. The conventional medical system uses a range from 0.30 – 4.0, but we often see people with symptoms of thyroid dysfunction within this range.
Free T4 (Thyroxine)
What it is: T4 is the main hormone produce by the thyroid gland. Free T4 is the amount of available or ‘active’ T4 in the body. Although there is more T4 in the body than T3, only around 10% of the T4 we have is metabolically active.
What it does: T4 is converted to T3, which is used by the cells of our body to increase metabolism and energy.
Why it’s important: Indicates if the thyroid is producing hormones at the right level.
Free T3 (Triiodothyronine)
What it is: The most active thyroid hormone and the best marker for monitoring thyroid function, clinical symptoms, and treatment.
What it does: T3 is “the gas” that acts on the cells of the body to increase metabolism, energy, and growth. When your T3 is low, you will likely be feeling symptoms of hypothyroidism regardless of what your T4 and TSH levels are.
Why it’s important: Indicates if T4 is converting properly to T3, and if there are high enough levels of active thyroid hormones present in our cells. This is a widely overlooked test that absolutely needs to be included as part as a thorough thyroid panel. I find this lab value best correlates to how patients are feeling day to day.
Reverse T3 (RT3)
What it is: RT3 is the inactive form of T3, which is formed from T4 under certain conditions (such as stress)
What it does: This is “the break”, as it blocks T3 from doing its job correctly.
Why it’s important: Can be increased due to factors such as stress, obesity and inflammation. If RT3 is high, other thyroid lab values can be normal but you can still be symptomatic.
Thyroid Antibodies (TPOAb, TGBAb, TSI)
What they are: Antibodies are produced by our immune system and attack the thyroid gland directly, affecting its ability to function. These include Thyroid Peroxidase Antibodies (TPO Ab), Thyroid Stimulating Immunoglobulin (TSI), and Thyroglobulin Antibodies (TGB Ab).
What it does: The presence of these suggest inflammation and destruction of the thyroid gland, as part of an autoimmune thyroid condition, such as Hashimoto’s or Grave’s disease.
Why it’s important: The presence of antibodies indicates an autoimmune (and therefore, inflammatory) process. Current statistics state that autoimmune hypothyroidism is responsible for up to 90% of all cases of hypothyroidism in women! Autoimmunity is essential to rule in or out, as this greatly changes the way we as Naturopathic Doctors treat thyroid conditions.
Other:
The thyroid is greatly affected by other hormones, nutrients, and vitamins. Other lab tests that may be important include Vitamin D, ferritin (iron stores), estrogen, progesterone, and cortisol. Stay tuned for future posts on how these factors directly affect thyroid function.
If you suspect your thyroid isn’t functioning properly or are currently on thyroid medication but still aren’t feeling well, a full thyroid panel investigating all of the above values can not only help reveal what’s really going on but can also guide the best treatment protocol for you and your body.
Got questions? We’re here to help.
Dr. Katie