WHY WOULD MY DOCTOR ORDER A THYROID SCAN?

The thyroid is a butterfly-shaped gland in the front of the neck. It produces hormones that play a key role in regulating blood pressure, body temperature, heart rate, metabolism, cholesterol levels, and women’s menstrual cycle.  

When the thyroid gland isn’t functioning properly, it may produce too much or too little hormone. It can also become enlarged or develop lumps of extra tissue. 

A thyroid scan is a type of nuclear medicine imaging that is primarily used to assess the function of the thyroid gland and detect any abnormalities. This scan evaluates how well the thyroid absorbs a radiotracer (radiopharmaceutical) that is injected into a vein in the arm. The resulting images help diagnose and monitor a condition known as hyperthyroidism (overactive thyroid). This occurs when the thyroid produces too much thyroid hormone, leading to symptoms like weight loss, rapid heartbeat, fatigue, and anxiety. A thyroid scan can help determine the cause, such as Graves’ disease or toxic multinodular goiter. 

WHAT HAPPENS DURING MY EXAM?  

Prior to your exam, you will need to ensure you’ve not had any injections from CT, X-ray or angiograms within one month prior to your test. You will need to stop taking all thyroid medications, and all multivitamins and/or supplements containing iodine two weeks prior to your appointment. See the list of medications to stop taking and consult your doctor prior to stopping them.  

Please notify your technologist if you are claustrophobic, if there’s a chance you may be pregnant, or if you are nursing. If you are pregnant, the exam will need to be postponed. If you are uncertain, a blood test will be required to confirm you are not pregnant prior to starting the exam. This may delay or postpone your appointment if not obtained in advance. If you are nursing, you will be given further instructions regarding breastfeeding.  

A radiopharmaceutical will be injected into an arm vein and travels throughout the body. The radiopharmaceutical will accumulate in the thyroid where it gives off gamma rays. After 5-10 minutes, you will be asked to lie on your back on the imaging bed while a gamma camera will be placed over your thyroid. The camera will be positioned very close over your head but will not touch you. The specialized camera detects the gamma rays emitted from your thyroid and, with the help of a computer creates detailed images. Areas that have a higher uptake of the radiotracer show up as different degrees of brightness in the scan (“hot” spots), which give information about how the thyroid is functioning and the structure. During imaging you will be asked to hold as still as you can. Movement can blur the images and make it more difficult to interpret.  

The radiopharmaceutical is excreted from the body through your urine and will decay within the body over the 48 hours following your exam. Keeping hydrated and voiding frequently will help eliminate it from your body. 

HOW DO I GET A THYROID SCAN?  

This exam is covered under your Alberta Health Care Insurance Plan and must be requested by a health care practitioner. If it’s indicated as a best next course of action, your doctor will provide you with a requisition and the appointment can be booked. 

Thyroid exams are only performed at our Mayfair Place location, please visit our exams & prep instructions page for more information about this exam. 

REFERENCES 

Anna Giorgi (2018) “Thyroid Scan”. www.healthline.com. Accessed May 9, 2025.  

WebMD Editorial Contributors (2023) “What Does Your Thyroid Do?”. www.webmd.com/. Accessed May 9, 2025. 

Dr Chian Chang and Dr Dee Nandurkar (2018) “Nuclear Medicine Thyroid Scan”. www.insideradiology.com.au/. Accessed May 9, 2025.