Blood sample is taken to check the thyroid function. A common check is T3, T4 and TSH. Sample can be taken at any time but it is better taken in the morning.
A total T3 or T4 does not always reflect the metabolically available thyroid hormone in the body as this depends on the amount of binding protein in the blood.
This is particularly important in women, pregnancy and certain medications. In this situation, the better test is free T4. In most of the cases, we do not need free T3.
The commonly available thyroid antibody test is for thyroid microsomal antibody (TMA) and thyroglobulin antibody (TGA). Most of the time they are not helpful in clinical practice as positive antibody rate is high in general population and relatives of people with thyroid disease.
TSH receptor binding antibody is helpful in particular situations but it is a little costly.
Ultrasound Scan of Thyroid
There are definite indications for this scan, everybody with a goitre or thyroid problem does not require this. Certain ultrasound picture can help in differentiating benign from the malignant thyroid nodule. It is the best test to see cyst in the thyroid.
Radioisotope Scan for Thyroid
Radioisotope scan is used to assess the activity of thyroid gland. A small amount of radioisotope (2-5mCi – which will not affect the function of the gland) is given either as a pill or liquid and images of the gland are taken afterwards.
Normal thyroid gland takes this uniformly and a small amount is also taken up by the Salivary glands. If the substance is avidly taken up by the thyroid gland, then whole of the thyroid gland is seen very prominent and salivary glands do not get an opportunity to take up any iodine. This is called overactive thyroid.
A small area may pick up whole of the iodine and rest of the gland does not get a chance because the small area is overactive, this is called HOT nodule, a hot nodule is almost never cancer. It may happen that whole of the thyroid picks up iodine other than a small area, this is called COLD nodule.
Sometimes the results are confusing when in spite of high levels of Thyroid hormones, the scan can show decreased uptake and this is called Thyroiditis. So, we can expect five different kinds of reports – Normal uptake, diffusely increased uptake (Graves’ disease), Hot nodule, Cold nodule and Thyroiditis.
Fine Needle Biopsy of Thyroid
This is done to diagnose thyroid cancer. Again a negative test does not necessarily rule out cancer. This is a simple out-patient procedure where a small needle in pushed into the goiter and the fluid extracted is seen under microscope to see the type of cells. In case of overactive thyroid we should not do this test.
Other Tests For Thyroid
A CT scan is of help to see a goitre which has extended inside the chest. A simple X-ray of the neck and chest sometimes we get to see the shadow of air-pipe (trachea).
An ENT exam is helpful to see the position of the vocal cord as the movement of the vocal cord can get affected by a goitre. ESR can be a valuable support for a diagnosis of the inflamed Thyroid gland called Thyroiditis.