Thyroid Tests
Screening And Testing For Thyroid Disease

Thyroid testing

Thyroid Screening


How Do Doctors Test For Thyroid Disorders?
Physical Examination
Blood Tests
Radioactive Iodine Scan
Thyroid Ultrasound Scan
Fine Needle Aspiration Biopsy
Core Needle Biopsy

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Thyroid Disease

How Do Doctors Test For Thyroid Disorders?

In recent years thyroid tests have become more and more sensitive which means doctors can identify people with a thyroid disorder before they even start to show symptoms. This is important because even at an early stage a thyroid disorder can be damaging to your body and it will nearly always progress to full-blown. Given that nearly 1 in 10 women will develop thyroid disease at some stage in their life, it makes sense for all women after the age of 35 to be screened every 5 years. Testing involves a physical examination and taking blood samples. There are numerous blood tests which can measure your thyroid function, but the best and most sensitive are the newer ones called free thyroxine (FT4 or T4) and thyroid-stimulating hormone (TSH). These tests tend to be the most accurate. If your doctor is only screening for thyroid problems, he may just perform one of the blood tests. Ideally, it should be the TSH test because it is the simplest to carry out and is the most accurate. If abnormalities are found, your doctor may order other tests to determine the cause before recommending treatment. We discuss all these procedures below.

Physical Examination

The first thing your doctor will do is quiz you on any symptoms you may be experiencing. For this reason, be sure to read our article on the symptoms of thyroid disease and make any notes before visiting your doctor. If you have a symptom, but always had it, it is not likely to be a thyroid issue. However if the symptom is relatively new, it is more likely to be. Also, be sure to read about the causes of thyroid disease, and mention if you have any of the risk factors such as you’ve had radiation to the neck, or you’ve been taking medications like lithium or amiodarone. Your doctor will carry out a full physical examination, examining your thyroid gland for signs of goiter, heartbeat and skin for changes like swelling or dry discolored patches (indicating hypothyroidism). If your skin is moist, your fingers tremor and you have a rapid pulse this could indicate hyperthyroidism.

Blood Tests

The physical examination is normally enough to confirm if someone has a thyroid disorder, but a clinical diagnosis will never be given without blood tests. These tests are:

TSH Test: This is the most sensitive of all thyroid blood tests. It measures how much T4 hormone the thyroid gland is being asked to make. If TSH levels are high it means you have hypothyroidism, if it's low you have hyperthyroidism. A normal TSH result range is between 0.5 and 5 mU/ml. However, many endocrinologists believe that this range is too wide and should be narrowed to 0.5-2.5 mU/ml.

T4 Test: This tests how much of the hormone thyroxine (T4) is knocking around freely in your bloodstream. If the level is high, you have hyperthyroidism and if it is low you have hypothyroidism. A normal T4 result is around 1-3 ng/dl or 3.1-6.8 pmol/L.

T3 Test: The free triiodothrronine (F3) blood test is rarely necessary, except where a person is showing symptoms of hyperthyroidism but their T4 results came back normal. A normal T3 result is 80-180 ng/dl or 12–22 pmol/L.

Antibodies Test: If your T4 and TSH tests come back positive, your doctor may order an antibody test to help determine the cause of your condition. High levels of TPOAb antibodies in your blood indicate Hashimoto’s disease. High levels of TRAb thyroid stimulating antibodies indicate Graves disease.

Non-Blood Tests
If a doctor has trouble determining the cause of your thyroid problem, he may order further diagnostic tests to check the size, shape and inner content of your thyroid. These tests are generally quite painless.

Thyroid Radioactive Iodine Scan

This test needs to be carried out in a hospital with a nuclear medicine laboratory facility. The patient is given a radioactive capsule to swallow. Doctors use a scan device (like a Geiger counter) to measure the uptake of iodine by the thyroid after 6 hours and after 24 hours. A normal thyroid-take up is between 5 and 25 percent, whereas an overactive take-up is over 35 percent. Also, the pattern of uptake can give an indication of problems. A 'cold' area with little uptake indicates a nodule (bump) which could be cancerous. Today, doctors in America don't often perform this test, because the blood tests are sensitive enough to give an accurate diagnosis. However, it may be used if cancer is suspected and as a way of managing people undergoing treatment for thyroid cancer.

Thyroid Ultrasound Scan

This is a simple ultrasound scan, similar to the type carried out in pregnant women - except it is used to scan the neck instead of the tummy. The patient lies down on an examination table and a gel is spread over the neck. A transducer is passed over the neck which sends sound waves to a computer which gives real-time images of your thyroid. It is usually ordered for people who have thyroid nodules. It can tell if the nodules are fluid filled (rarely cancer) or solid, which may be cancer.

Fine Needle Aspiration Biopsy (FNAB)

If your doctor is worried about the results of your ultrasound scan, he may wish to perform a FNAB to take a sample of tissue from your thyroid, or a nodule on the thyroid. This is a relatively painless procedure which requires no anesthesia. A small needle is inserted into the thyroid and a plunger is drawn to remove a tiny sample of tissue. It may be necessary to use an ultrasound scan to guide the needle to the correct place. The tissue is then sent to a lab to test for cancer. Sometimes a doctor may even skip the iodine scan and ultrasound scan step and go direct to an FNAB.

Core Needle Biopsy

If results from an FNAB are not conclusive, it may be necessary to take a bigger sample of tissue. This is done by a core needle biopsy. Basically, the needle is bigger, so the sample is bigger. It is carried out with local anesthetic on an outpatient basis. The procedure takes about 30 minutes and you will be monitored for bleeding for a further 30 minutes.

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