After thyroid cancer has been treated, lifelong monitoring is also performed. This is for two main reasons: First, long-term monitoring helps to ensure that the appropriate dose of thyroid hormone therapy is administered, neither too much nor too little. Second, to monitor for persistence or recurrence of thyroid cancer. Many patients with differentiated thyroid cancer will have cancer persistence or cancer recurrence. If recurrence can be detected early, most patients still have a good prognosis. Therefore, long-term surveillance is very important. The exact method and frequency of monitoring depends on the size of the primary tumor, whether it has metastasized to other sites, and several other factors. Monitoring does not need to be as frequent in patients without signs of cancer recurrence compared to those with persistent cancer. The interval of monitoring can be extended when the patient is clinically cured of cancer. A discussion should be held between the physician and patient to develop an individualized monitoring plan that is appropriate for the patient’s situation. Monitoring often includes: Neck examination: including palpation of the thyroid bed area. This is usually done every 3-6 months for 2 years after surgery and at least annually thereafter. Blood tests: Thyroid function is measured to evaluate the appropriateness of the dose of thyroid hormone therapy, and the thyroxine dose may be adjusted based on thyroid function. Blood tests are also helpful in monitoring for recurrence of thyroid cancer. The specific indicators of blood tests are related to the type of thyroid cancer. Neck ultrasound: The use of neck ultrasound is increasing because it is a sensitive way to detect lesions in the neck. When an ultrasound is done, a probe is slid over the neck without causing a painful meal and without radiation.