Thyroid Blood Tests: Types, Symptoms and Interpreting Test Results

Your body has several glands to perform various body functions. The thyroid is a small gland located at the front of the neck, right at the spot where a bow tie would rest. It makes two types of thyroid hormones: triiodothyronine (T3) and thyroxine (T4). It helps your body maintain its metabolic rate, and do numerous other things, including getting energy from food, growing, and going through sexual development.

Thyroid Tests

The thyroid blood tests (also called thyroid panel) are simple lab tests that check if your thyroid is functioning right or not. In people who have already been diagnosed with thyroid problems, the tests are used to monitor and guide treatment.

Types of Thyroid Blood Tests

• T4 Test: This test measures the levels of the hormone T4 (thyroxine) in your blood. It might be done in one or both of the following ways: Total T4, which measures the total amount of thyroxine in the blood. This includes the amount of T4 attached to blood proteins, which help the hormone move through the bloodstream; and free T4, which measures only the amount of free thyroxine that is not attached to blood proteins.

• T3 test: This test measures the level of another major thyroid hormone. It again can be of two types: T3 totaI and free T3.

• TSH Test: A thyroid-stimulating hormone (TSH) test is the most significant tool, in a way, to tell how well the thyroid is working. If you have any problem related to the thyroid gland and it prevents the gland from making enough thyroid hormone, another gland, called the pituitary gland, releases more TSH into the blood. If the thyroid is making too much thyroid hormone, the pituitary releases less TSH, which means less TSH levels in the blood.

• Thyroid antibodies test: There is one thyroid condition, called Hashimoto's thyroiditis, which is an autoimmune condition. This means the body's own immune system attacks the thyroid gland. A test that checks for high levels of antibodies helps detect this condition. Antibodies are a sign of the immune system going awry and attacking the thyroid gland. Generally, two types of thyroid antibodies are measured: thyroglobulin antibodies (TgAb) and thyroid peroxidase antibodies (TPO).

Symptoms and Diagnosis

• A high TSH level most often means you have low thyroid hormone levels in the blood (condition is called hypothyroidism), or an underactive thyroid. This implies that your thyroid isn't making enough hormones. As a result of which the pituitary gland has to make and release extra TSH into your blood to stimulate the thyroid gland.

• A low TSH level usually means you have high thyroid hormone levels in the blood (condition is called hyperthyroidism), or an overactive thyroid. This implies that your thyroid gland is making excess hormones, and that is why the pituitary gland has reduced or stopped making and releasing TSH into your blood.

• A high T4 level may mean you have hyperthyroidism. A low level of T4 may mean you have hypothyroidism.

• If the TSH levels are elevated, T4 levels are normal to low, and T3 levels are normal, it might indicate early hypothyroidism.

In some cases, high or low T4 levels may not mean you have thyroid problems since the levels might be affected due to factors such as pregnancy, certain medicines (oral contraceptives, corticosteroids, etc), severe illness, and other health problems. Basically, these conditions and medicines alter the number of proteins in your blood that “bind,” or attach, to T4.

Please note that your doctor is the best guide to interpret your thyroid test results and suggest the diagnosis.

Hypothyroidism
If your thyroid is underactive, it makes too little thyroid hormone, which leads to hypothyroidism. Your body's metabolic rate goes down and it uses up energy more slowly. Symptoms include tiredness, feeling cold, constipation, dry skin, infrequent menses or absent periods in women, and slow height growth in children.

Hyperthyroidism
If your thyroid is overactive, it releases too much thyroid hormone, which leads to hyperthyroidism. Your body's basal metabolic rate goes up and it uses up energy more quickly than it should. Symptoms include sweating, trembling, weight loss, diarrhea, irregular menses or (increased bleeding which might also occur) in women, and fast heartbeat.

Why You May Need a Thyroid Test?

It is not uncommon to have hypothyroidism and still being unaware of the condition. It might take some time for symptoms to be noticeable. Regular thyroid screening helps get diagnosed on time and seek early treatment. It is more important to get tested if thyroid conditions run in your family. The more family members that have thyroid disease, the higher the chances the person will experience a thyroid disease.

Moreover, women of all ages are more likely than men to have low thyroid hormone levels.

If you're 60 or older, it's a good idea to check with your doctor to see whether your medical history suggests you might benefit from getting testing for thyroid levels.

What You Can Do

If you seem to have any of the symptoms of low or high thyroid levels, talk to your doctor and get tested as advised. Do not ignore any health symptoms. Getting the right treatment can help you get complete control of your thyroid-related symptoms.