iThei mdcdaelcinfd o c elllllrlllll tThe hlcinfd olsbdkpvouvEven with all of the redefined normal ranges, TSH screening only catches
the late stage of Hashimoto’s since the body is still able to compensate in
the beginning stages of thyroid dysfunction.
Hormone Tests
T4 (thyroxine) and T3 (triiodothyronine) are the two main thyroid hor-
mones. Known as a prohormone, T4 is 300 percent less biologically ac-
tive than T3, the main biologically active thyroid hormone.
There are two ways to test the thyroid hormones. Total hormone levels
measure all of the thyroid hormones in the body, but they may not paint
an accurate picture of the situation. “Free” hormone levels measure the
hormone available to do its job in the body. Thus, tests for free T4 and
free T3 are recommended.
Some clinicians may only test for T4, but it is also important to test T3
as some individuals may not be properly converting T4 to the active T3.
Some people may have a normal T4 but a low T3 level.
The reverse T3 (rT3) test measures how much of the free active T3 is able
to bind at thyroid receptors. RT3 is produced in stressful situations and
binds to thyroid receptors but turns them off instead of activating them.
Best Test for Hashimoto’s
In most cases of Hashimoto’s thyroiditis, blood tests reveal one or two
types of anti-thyroid antibodies. Thyroid peroxidase antibodies (TPOAb)
are the most common, but antibodies against thyroglobulin (TGAb) are
often found as well. These antibodies may appear decades before a change
in TSH is detected.
Thus, TPO antibody screening is always crucial in suspected thyroid
disease.
RECOMMENDED THYROID FUNCTION TESTS• TSH
- TPO Antibodies
- Thyroglobulin Antibodies
- Free T4
- Free T3
- Reverse T3 (Optional)