Do you suffer from multiple thyroid symptoms, but your doctor keeps telling you that your thyroid tests are normal? Do you feel in your gut that something is still going on with your thyroid? This is a situation I commonly see with patients in practice. The problem is that the standard for thyroid testing (TSH) does not yield a complete picture of what is happening with the thyroid gland.
If you have a feeling that your thyroid is not functioning well but your lab work always comes back “normal” you may want to consider the following lab tests to fully assess thyroid function.
A Full Thyroid Panel Includes:
TSH (Thyroid Stimulating Hormone)
This is the standard screening test for thyroid function. It indicates the level of stimulation from the pituitary gland to the thyroid gland to produce thyroid hormones (T4 and T3). A high level indicates the thyroid is under-functioning; meaning that a high level of TSH is being produced to stimulate the thyroid gland but it may not be responding adequately to release thyroid hormones. A low TSH level indicates over-functioning; meaning that very little TSH is being released because the production of thyroid hormones is already high.
Optimal levels: The lab range is range is 0.32 - 5.04. The optimal range sits between a more narrow range of 1.0-2.0. Symptoms of thyroid dysfunction can start to manifest above this range.
Free T4 (Thyroxine)
~90% of the thyroid hormone produced in the body is in the form of T4. This is an inactive, storage form of thyroid hormones that needs to be converted to T3 in the tissues to be metabolically active.
Optimal levels: The lab range is 10.6 - 19.7. Most people feel best when free T4 is in the mid-to-upper end of the range (15+)
Free T3 (Triiodothyronine)
T3 is the active form of thyroid hormone. It is the best marker of thyroid function and correlates most closely with symptoms. T3 acts on all tissues in the body to influence functions such as metabolism, energy and growth. It is important to assess the T3 in relation to T4 levels. If T4 is converting properly to T3 in the tissues, there should be an optimal level of T3 in the cells. If T4 levels are high and T3 is low, there is poor conversion.
Optimal levels: The lab range is 3.0 - 5.9. Most people feel their best when T3 is in the upper end of the lab range (4.5+)
Thyroid Antibodies (TPOAb, TGAb, TSI)
Antibodies can be produced by our immune system to attack the thyroid gland and target its tissue for destruction. These antibodies include thyroid peroxidase antibodies (TPO Ab), thyroglobulin antibodies (TG Ab) and thyroid stimulating immunoglobulin (TSI). The presence of these antibodies indicates autoimmune destruction of the thyroid gland. ~90 of hypothyroidism is caused by an autoimmune condition called Hashimotos Thyroiditis. Because conventional medicine does not have a treatment approach to address the autoimmune reaction, it is not a standard screening test because it does not influence the conventional treatment approach. From a naturopathic perspective, determining the presence of antibodies is essential for tailoring a treatment plan that addresses the root cause of autoimmunity and thyroid dysfunction.
Other Useful Tests to Consider:
Reverse T3 (rT3)
This is an inactive form of T3 that is produced from T4 under conditions such as chronic stress or illness. Reverse T3 binds T3 receptors and blocks the action of normal, active T3. It blocks active T3 from effectively doing its job.
Thyroid Binding Globulin (TBG)
Thyroid binding globulin is a carrier protein that binds thyroid hormones and carries them to tissues. When a high level of TBG is produced, there is a high level of thyroid hormone bound and unavailable to tissues. When this happens TSH levels will rise to try to produce more free T4 and T3 that is unbound and available to tissue.
Low levels of Vitamin D, ferritin (iron stores) and B12 are commonly associated with thyroid dysfunction. Supplement form and dosing can be adjusted as needed to each individual's needs.
Gluten Sensitivity testing:
There is a strong correlation with thyroid dysfunction and gluten sensitivity/celiac disease. It is so strong, that many practitioners recommend gluten avoidance regardless of testing.
Often multiple hormone imbalances will present at the same time. Tests to consider include: estrogen, progesterone, cortisol and insulin.
Helps to visualize abnormalities of the thyroid gland (such as nodules or cancer) and measure the extent of thyroid enlargement/inflammation.
If you suspect your thyroid is not functioning optimally, a full thyroid profile and the additional testing options above may help get to the root cause of your symptoms. Testing is also indicated when you are on thyroid medication but do not notice improvement in symptoms despite “normal” TSH levels. Comprehensive testing is extremely valuable for guiding an individualized treatment plan.