How Is Thyroid Disease Diagnosed?

Thyroid disease occurs when the thyroid—a small butterfly-shaped gland in the neck—makes too much or too little thyroid hormone. Your thyroid hormone controls many of the body’s functions such as metabolism, temperature, and heart rate.

There are two main types of thyroid disease—hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid). Hyperthyroidism occurs when you have too much thyroid hormone, which may result in symptoms such as weight loss, rapid or irregular heartbeat, and trouble tolerating heat. Having too little thyroid hormone is known as hypothyroidism, which can produce symptoms like weight gain, fatigue, and a slowed heart rate.

If you notice symptoms of thyroid disease or may be at risk of developing the condition, it’s good practice to see your healthcare providers. During your appointment, your provider will take a thorough medical history, perform a physical exam, and can order blood tests and imaging tests if necessary. 

Medical History and Physical Exam

At your visit, your healthcare provider will ask you about your personal and your family’s medical history. This helps them learn more about your background, current symptoms, and lifestyle habits. 

Your provider may ask you several questions that may include: 

• What symptoms are you experiencing?
• How long have you had these symptoms?
• Does anyone in your family have a history of thyroid disease?
• Have you previously had any concerns about your hormones?
• Has a provider ever tested your thyroid hormone levels?
• Are you taking any medications?
• Have you experienced any recent major life changes?
• Do you have any other health conditions?

After learning about your medical history, it’s standard practice for your healthcare provider to conduct a physical exam. During your exam, your provider may:

• Measure your weight to discuss any drastic changes 
• Take your vital signs (e.g., heart rate, blood pressure, body temperature)
• Examine your throat to feel your thyroid gland and look for any signs of an enlarged thyroid or nodules (small bumps) 
• Listen to your thyroid gland with a stethoscope to hear any potential issues with blood flow 
• Check for the presence of lymph nodes
• Look at your face, skin, and hair health—which can all be affected by thyroid disease 

Your medical history and physical exam can help your provider get a better understanding of your condition and figure out how to move forward with additional testing if necessary.  

Blood Tests

Blood tests are a routine part of thyroid testing. Blood testing doesn’t usually doesn’t occur on the same day as your initial appointment, so it is likely that your provider will have you schedule a different appointment to get your blood tests done. 

The most common thyroid-related blood tests check for:

• Thyroid stimulating hormone (TSH): TSH is made by the pituitary gland and tells the body how much thyroid hormone to make. High TSH levels mean that your thyroid hormone levels are too low, which can mean you have hypothyroidism. Low TSH levels indicate that thyroid hormone levels are too high, which can be a sign of hyperthyroidism. 
• Thyroxine (T4): T4 is one of the main thyroid hormones. If your blood test shows you have too little T4, you may be at risk for hypothyroidism. On the other hand, too much T4 can be a sign of hyperthyroidism, goiter (an enlarged thyroid), or thyroid nodules.
• Triiodothyronine (T3): T3 works in conjunction with T4 to regulate how the body uses energy. High levels of T3 can indicate hyperthyroidism, while low levels of T3 are often associated with hypothyroidism.

If one or more of your results for these blood tests are in an abnormal range, your healthcare provider may also order additional blood tests that check for thyroid antibodies (or, proteins in your immune system that fight harmful cells in your thyroid gland). Antibody tests can help you and your provider learn whether you have an autoimmune condition—like Graves’ disease or Hashimoto’s disease—which are the primary causes for hyperthyroidism and hypothyroidism, respectively.

Imaging Tests

Blood tests can often give your healthcare provider a better picture of your condition. But in some cases, your provider may choose to order imaging tests—especially if they notice an enlarged thyroid or the presence of thyroid nodules. 

These imaging tests may include:

• Ultrasound: An ultrasound uses painless sound waves to create pictures of the thyroid. Your provider can use an ultrasound to look for nodules or lumps and determine whether they are cancerous or not. If your provider notices any lumps during your ultrasound, they may recommend a biopsy to take a small tissue or fluid sample to rule out thyroid cancer.
• Thyroid nuclear scan or radioactive iodine uptake test: During this test, you can either swallow a small amount of iodine in pill or liquid form or ask for the iodine to be injected into your body. The iodine then travels to the thyroid, where your provider can check how much iodine your thyroid takes up. If your thyroid uses a lot of iodine, this could be a sign of Graves’ disease, thyroiditis (thyroid inflammation), or an enlarged thyroid. 
• Computed tomography (CT) or magnetic resonance imaging (MRI) scans: These scans can produce detailed images of your thyroid and provide more information about the presence of any nodules, lumps, or an enlarged thyroid.  

Screening for Related Conditions

Symptoms of hypothyroidism and hyperthyroidism can often mimic the symptoms of other conditions. As a result, thyroid testing is important to help rule out other conditions. 

Nonspecific thyroid disease symptoms like fatigue, weight loss or gain, and changes to the skin and hair are also associated with conditions such as:

• Anemia
• Addison’s disease 
• Chronic fatigue syndrome
• Iodine deficiency 
• Fibromyalgia 
• Diabetes 

Other health conditions can also co-occur with thyroid disease—which are known as “comorbidities.” If you have a type of thyroid disease, you may be at an increased risk for developing conditions such as:

• Thyroiditis 
• Depression
• Heart disease
• High blood pressure 
• Fertility issues