Appropriately testing thyroid function is an essential part of effectively recognizing and treating thyroid disease such as hypothyroidism and autoimmune thyroid disorders. Unfortunately, it is common practice for the medical community at large to rely solely on one type of test to assess thyroid function.
To properly diagnose thyroid disease and identify areas of dysfunction multiple areas must be tested. The National Academy of Hypothyroidism has created a lab slip indicating the necessary tests that must be done to assess thyroid function. The importance of each of these substances is explained below.
Thyroid Stimulating Hormone (TSH)
Thyroid stimulating hormone or TSH is a hormone that relays information between the pituitary and thyroid gland. The pituitary releases TSH to promote the production of T4. Elevated TSH levels are generally indicative of hypothyroidism. TSH levels are the most common metric used to assess thyroid function. However, on its own it is not an adequate measure of thyroid function.
Thyroxine (Free T4)
Thyroxine (T4) is the inactive form of thyroid hormone that is ultimately converted into triiodothyronine or reverse triiodothyronine. A deficiency or excess of T4 can indicate thyroid imbalance. Hypothyroid patients typically have reduced levels of T4 while hyperthyroid patients generally have elevated levels.
Triiodothyronine (Free T3)
Triiodothyronine (T3) is perhaps the most important metric of thyroid function. T3 is converted from T4 and, as the active form of thyroid hormone, influences numerous bodily functions. Increased T3 levels are indicative of hyperthyroidism and decreased levels typically points to hypothyroidism.
Reverse Triiodothyronine (Reverse T3)
Reverse T3 is the mirrored version of T3 and is also converted from T4. This regulatory hormone inhibits T3 activity to protect against overactivity. Over conversion of T4 to Reverse T3 often results in hypothyroidism. Hypothyroidism caused by increased levels of Reverse T3 is typically not recognized when testing other thyroid hormones.
Thyroid Antibodies (TPOAb, TGAb and TSI)
Increased levels of thyroid antibodies in the form of Thyroid Peroxidase Antibody (TPOAb), Thyroglobulin Antibody (TGAb), and Thyroid-Stimulating Immunoglobulins (TSI), can indicate the presence of autoimmune thyroid disorders such as Hashimoto’s thyroiditis and Graves’ Disease.
Sex Hormone-Binding Globulin (SHBG)
Sex Hormone-Binding Globulin (SHBG) is involved in the transport of various hormones including testosterone, estrogen, and thyroid hormones. SHBG binds to hormones and directs them to the appropriate system. Poor hormone transport can result in hypothyroidism.
Reduced leptin levels can result in poor hypothalamic activity. Limited hypothalamic action often leads to inhibited TSH production and reduced thyroid function. Leptin resistance, which may be identified through testing, is often seen in those with poor T4, T3, and Reverse T3 levels.
Iodine is an essential building block for thyroid hormones. A deficiency of iodine frequently results in poor thyroid function and a lack of thyroid hormones thereby prompting hypothyroidism. Alternatively, an excess of iodine may result in hastened thyroid function or hyperthyroidism.
Getting the Testing You Need
Thyroid testing is critical for accurately diagnosing and treating thyroid disease. Utilizing the pre-marked lab slip provided by the National Academy of Hypothyroidism makes requesting the appropriate tests easy. Make sure your thyroid is functioning at its best by having a thorough thyroid exam that includes all of the essential substances indicated on the NAH thyroid lab slip.