The thyroid is a butterfly-shaped gland located in the neck that is responsible for producing several hormones that regulate most of the body's metabolic activities. Diseases of the thyroid can cause too much hormone, a condition known as hyperthyroidism, or too little hormone, known as hypothyroidism. The Colorado Thyroid Disease Prevalence Study, published in the "Archives of Internal Medicine" in 2000, found that there may be more than 13 million Americans suffering from unrecognized thyroid disease. Because the symptoms of the disease often develop gradually and can indicate a variety of conditions, thyroid disease can be difficult to diagnose. Doctors can use several tests, however, to determine an accurate diagnosis.
Physical Examination
The initial test performed to determine the cause of symptoms is a thorough physical examination. The doctor should do the following as part of the exam: measure height and weight, test reflexes, measure heart rate and rhythm, measure blood pressure, listen to the thyroid using a stethoscope, feel glands in the neck and examine the face, eyes, skin, nails and hands.
Swollen glands in the neck may contribute to thyroid dysfunction. A racing heart rate, or pulse, may indicate an increase in metabolism, which may be caused by too much thyroid hormone. Eye irritation or protrusion may signal the presence of Graves' disease, a form of hyperthyroidism that can affect the tissue behind the eyes.
Blood Test
When the results of the physical examination indicate that there may be an issue with the thyroid, blood tests can be performed to provide further information. Specific blood tests measure the levels of the two thyroid hormones--thyroxine (T4) and triiodothyronine (T3)--to determine if there is too little or too much. Tests can also measure Thyroid Stimulating Hormone (TSH), a hormone produce by the pituitary gland that signals the thyroid to produce thyroid hormones. Too much TSH can result in too much thyroid hormone.
Radioactive Iodine Uptake
A radioactive iodine uptake test determines thyroid function and can measure the amount of thyroid hormones being produced. To perform the test, an iodine substance that contains radionuclides (slightly radioactive material) is administered to the patient either intravenously or orally as a pill.
The thyroid gland absorbs iodine and uses it to create thyroid hormones. Therefore, when the gland is producing large amounts of thyroid hormone, it uptakes more iodine, which will increase the radioactive material present. The doctor uses a probe similar to a Geiger counter to measure the percentage of radioactivity present in the gland.
Thyroid Scan
A thyroid scan creates a picture of the gland so doctors can visualize any lumps or inflammation present. To perform the scan, the same type of radioactive iodine substance in administered to the patient, and then a radioactivity detector camera is used to take pictures of the neck. According to Harvard Medical School, the pictures, which are developed in about an hour, show the outline, shape and position of the thyroid, which can help determine any disease.
