Tests to Diagnose Thyroid Nodules

Physical exam. Thyroid nodules are usually palpated when examining the anterior neck area. The nodule and the entire thyroid gland are examined to assess whether the nodule is single or multiple. It is also checked to see if the size of the nodule means it is affecting other anatomical structures. A general physical examination is performed to determine whether the thyroid gland is functioning normally or if there are signs of hyperthyroidism or hypothyroidism. Occasionally, depending on the anatomy of the individual, thyroid nodules may be located lower in the upper chest and therefore cannot be detected by palpation. 

Blood test. Normally, nodules do not alter the function of the thyroid gland. However, to detect if the nodule is behaving autonomously, i.e., it has overproduced thyroid hormone and caused hyperthyroidism, an initial blood sample is analysed for thyrotropin (TSH), the hormone that controls the function of the thyroid gland, and free thyroxine (T4L). If TSH is low and T4L is high, the patient has hyperthyroidism.  

Thyroid ultrasound. This is the standard test for scanning thyroid nodules. It detects even tiny nodules (as small as 1 mm, which have little clinical impact), and determines whether they are cystic or solid, whether they have ultrasound features suggestive of malignancy, and the presence of cervical lymph nodes.  

The ultrasound can detect suspicious nodules based on a risk classification system and help to decide whether a cytological examination should be performed to remove them. Ultrasounds can be used to guide diagnostic fine needle aspirations, as well as in the percutaneous treatment of thyroid nodules: for emptying thyroid nodules with fluid (cysts) or reducing the size of symptomatic thyroid nodules through the skin.  

Ultrasound-guided fine needle aspiration (FNA). This test is used to take a cytological sample of thyroid cells by puncturing the thyroid and then studying the cells under the microscope to determine whether they are malignant or benign. The patient does not need to fast or stop taking any medication prior to the test, except for antiplatelet and anticoagulant drugs as these can increase the risk of bleeding, and so they are replaced with heparin. There are usually no complications that could impede normal activities after the procedure, although it is recommended that you do not do physical exercise on the same day, as it involves significant contraction of the cervical muscles. 

Thyroid gamma scan. This is an imaging test that is used in nuclear medicine to see if the whole thyroid is functioning homogeneously or if there is a particular part, or any nodules, that are working too much or too little. It is suitable for studying the origin of hyperthyroidism or thyroiditis.

Cervical and thoracic computed tomography (CT). This is used to determine the limits of the thyroid in large goitres or when the thyroid is suspected to be located lower in the chest, behind the sternum. It can also be used to see if the thyroid has grown posteriorly, behind the oesophagus, or inferiorly, behind the sternum.  

Magnetic resonance imaging. This is used on malignant nodules to see if they have spread to neighbouring structures.