Thyroid Testing and Diagnosis

Most conventional doctors rely on a test known as the TSH test to diagnose an overactive or underactive thyroid. The TSH test is a blood test that measures the amount of thyroid-stimulating hormone—TSH—in your bloodstream. (The test is sometimes also called the thyrotropin stimulating hormone test.) Elevated TSH levels can indicate hypothyroidism. Low or nonexistent TSH levels can indicate hyperthyroidism.

You'll need to know what the normal values are for the lab where your doctor sends your blood because "normal" varies from lab to lab.

Thyroid normal ranges are in tremendous flux right now. Throughout the 1980s and 1990s in North America, the "normal" TSH range was from about 0.3-0.5 at the bottom end, to a high end of from 5.0 to 6.0. In November of 2002, the National Academy of Clinical Biochemistry (NACB), part of the Academy of the American Association for Clinical Chemistry (AACC), issued revised laboratory medicine practice guidelines for the diagnosis and monitoring of thyroid disease, which prompted the American Association of Clinical Endocrinologists (AACE) to recommend a narrower margin of 0.3 to 3.0.

In the years since the original NACB guidelines were released, most laboratories and many doctors have yet to adopt these new guidelines, and the medical world is still not in complete agreement about changing the guidelines. This means that for patients who test above below 0.5, or above 3.0, whether or not you get diagnosed and treated for a thyroid condition depends on how up-to-date both your laboratory and practitioner are.

Free T4

Free T4 measures the free, unbound thyroxine levels circulating in your bloodstream. Free T4 is typically elevated in hyperthyroidism, and lowered in hypothyroidism.

Total T3/Total Triiodothyronine/Serum Triiodothyronine

Total T3 is a measure of the T3 bound to protein as well as the T3 that is free and unbound. The Total T3 level will typically be elevated in hyperthyroidism, lowered in hypothyroidism.

Free T3

Free T3 measures free unbound triiodothyronine in your bloodstream. Again, the "Free" levels are considered more accurate than the total in the case of T3.

Thyroglobulin/Thyroid Binding Globulin/TBG

Thyroglobulin, also known as thyroid binding globulin or TBG, is a protein, produced by your thyroid primarily when it is injured or inflamed, due to thyroiditis or cancer, and leaks thyroglobulin into the bloodstream. Normal thyroid produces low or no thyroglobulin, and so undetectable thyroglobulin levels usually mean normal thyroid function. Thyroglobulin is typically elevated in Graves' disease, thyroiditis, and thyroid cancer.

T3 Resin Uptake (T3RU)

When done with a T3 and T4, the T3 resin uptake (T3RU) test is sometimes referred to as the T7 test. This test can help assess whether your thyroid is actually dysfunctional thyroid, or whether hormones are binding in the bloodstream, causing abnormal results. Conditions causing hyperthyroidism typically increase T3RU.

Thyroid Peroxidase (TPO) Antibodies (TPOAb) / Antithyroid Peroxidase Antibodies

Thyroid Peroxidase or TPO Antibodies -- also known as Antithyroid Peroxidase Antibodies., frequently show up as a sign that the thyroid tissue is being destroyed, such as in Hashimoto's disease and in some other types of thyroiditis such as post-partum thyroiditis, and TPO antibodies are detectable in approximately 95% of patients with Hashimoto's thyroiditis. Some 50 to 85% of Graves' disease patients have them as well, but they are not a reliable stand-alone test for diagnosing Graves' disease.

Antithyroid Microsomal Antibodies / Antimicrosomal Antibodies

This test is typically elevated when you have Hashimoto's thyroiditis. It's thought that as many as 80 percent of Hashimoto's patients have elevated levels of these antibodies.

Thyroglobulin Antibodies / Antithyroglobulin Antibodies

Thyroglobulin antibodies (also called antithyroglobulin antibodies) in someone with hyperthyroidism confirm autoimmune disease -- but are not formally diagnostic of Graves' disease. Tg antibodies are positive in about 60% of Hashimoto's patients and 30% of Graves' patients.

Thyroid Receptor Antibodies (TRAb)

TSH receptor antibodies (TRAb) are seen in most patients with a history of or who currently have Graves' disease. TRAb may be:

• stimulatory, in which case they cause hyperthyroidism [TSH stimulating antibodies (TSAb)]
• blocking, in which case they prevent TSH from binding to the cell receptor, and cause hypothyroidism [TSH receptor blocking antibodies (TBAb/TSBAb)]
• binding, in which case they interfere with the activity of TSH at the cell receptor

Thyroid-Stimulating Immunoglobulins (TSI)

Thyroid-stimulating immunoglobulins (TSI) can be detected in the majority of Graves' disease patients, some say as many as 75 to 90%. Their presence of is considered diagnostic for Graves' disease. The higher the levels, the more active the Graves' disease is thought to be. The absence of these antibodies does not, however, mean that you don't have Graves' disease. Monitoring TSI may help predict relapse of Graves' disease, and lower TSI levels can indicate that a treatment is working. TSI is also monitored during pregnancy, as they are a risk factor for fetal or neonatal thyroid dysfunction.

Nuclear Scan / Radioactive Iodine Uptake (RAI-U)

Radioactive iodine uptake (RAI-U) is a test that is done to help differentiate between Graves' disease, toxic multinodular goiter, and thyroiditis. In this test, a small dose of radioactive iodine 123 is administered as a pill. Several hours later, the amount of iodine in your system is measured, often accompanied by an x-ray that views how iodine concentrated in your thyroid.

Almost all forms of hyperthyroidism show as higher uptake because an overactive thyroid usually takes up higher amounts of iodine than normal, and that uptake is visible in the x-ray. A thyroid that takes up iodine is considered "hot" -- or overactive, versus a cold or underactive thyroid.

In Graves', RAI-U is elevated, and you can see that the entire gland becomes hot. (In contrast, in Hashimoto's thyroiditis, the uptake is usually low, with patchy hot spots in the gland.) If you have thyroid nodules, RAI-U can show them and whether they are hot. If you are hyperthyroid due to a hot nodule, and not Graves' disease, the nodule will show up as hot, and the rest of your thyroid will be cold. Hot nodules may overproduce thyroid hormone, but they are rarely cancerous. An estimated 10 to 20 percent of cold nodules are cancerous, however.

CT Scan

A CT scan -- known as computed tomography or "cat scan" -- is a specialized type of x-ray that is used -- not very frequently, however -- to evaluate the thyroid. A CT scan can not detect smaller nodules, but it can diagnose a goiter, or larger nodules.

MRI / Magnetic Resonance Imaging

MRI is done when the size and shape of the thyroid needs to be evaluated. MRI can't tell anything about how your thyroid is functioning -- i.e., whether it is hyperthyroid or hypothyroid -- but can detect enlargement, and may be able to along side blood tests. It is sometimes preferable to x-rays or CT scans because it doesn't require any injection of contrast dye, and doesn't require radiation.

Thyroid Ultrasound

Ultrasound of the thyroid is done to evaluate nodules, lumps and enlargement of your gland. Ultrasound can also determine whether a nodule is a fluid-filled cyst, or a mass of solid tissue. Ultrasound cannot tell whether a nodule or lump is benign or malignant, however. In Graves' disease, the thyroid is usually enlarged. A reduction in the size of your thyroid is one of the first signs that you are responding to antithyroid drug treatment for Graves' disease. If you are on antithyroid drugs, therefore, your doctor may use ultrasound to monitor the success of your treatment.

Needle Biopsy / Fine Needle Aspiration / FNA

This technique helps to evaluate lumps or cold nodules. In a needle biopsy, a thin needle is inserted directly into the lump, and some cells are withdrawn and evaluated. In some cases, ultrasound is used to help guide the needle into the correct position. Pathology assessment of the cells can often reveal Hashimoto's thyroiditis, as well as cancerous cells. Definitive information is available in approximately 75 percent of nodules biopsied.

Other Blood Tests

There is other bloodwork that a physician may do to rule out thyroid disease, or to identify related conditions that may raise the suspicion of a thyroid condition. Besides thyroid tests, other blood test results that may be pointing to (but are not conclusively diagnostic of) thyroid conditions include:

• High sedimentation (aka, "sed" rate)
• Abnormal (high or low) cholesterol
• Abnormal (high or low) triglycerides
• Abnormal (high or low) iron or ferritin
• Elevated serum calcium
• Elevated alkaline phosphatase
• Elevated sex hormone-binding globulin levels
• Elevated blood sugar / Poor glucose tolerance
• Elevated hemoglobin A1C
• Elevated bilirubin
• Elevated aminotransferases
• Decreased free testosterone levels
• Elevated C-Reactive protein levels
• Elevated Homocysteine levels

Saliva and urinary thyroid testing are means of thyroid testing that a growing number of alternative or complementary practitioners are using. Some practitioners also use basal body temperature measurements to aid in diagnosis.

A Self-Check: The Thyroid Neck Check

One simple, at-home self-test that can potentially detect some thyroid abnormalities is a thyroid neck check. To take this test, hold a mirror so that you can see your thyroid area -- the neck, just below the Adam's apple and above the collarbone. Tip your head back, while keeping this view of your neck and thyroid area in your mirror. Take a drink of water and swallow. As you swallow, look at your neck. Watch carefully for any bulges, enlargement, protrusions, or unusual appearances in this area. Repeat this process several times. If you see any bulges, protrusions, lumps or anything that appears unusual, see your doctor right away. You may have a goiter (an enlarged thyroid), or a thyroid nodule, and your thyroid should be evaluated. Be sure you don't get your Adam's apple confused with your thyroid gland. The Adam's apple is at the front of your neck; the thyroid is further down, and closer to your collarbone. Remember that this test is by no means conclusive, and cannot rule out thyroid abnormalities. It's just helpful to identify a particularly enlarged thyroid or masses in the thyroid that warrant evaluation.

Note: You Can Order Your Own Laboratory Tests

Most states allow you to, through specialized services like MyMedLab, order your own thyroid blood tests. Find out more about how to order TSH, Free T4, Free T3, Thyroid Antibodies, and other blood tests, without a doctor's appointment, and without a doctor's orders, now.