An occasional neck ct exam is generally not harmful to the thyroid, but if frequent neck ct exams are performed, they may be harmful to thyroid cells. Neck ct examination scanning range is more extensive, can be checked to the pharynx, larynx, thyroid, tonsils, cervical intervertebral discs, etc., whether there is a lesion, in general, occasionally do a cervical ct examination generally will not cause any harm to the thyroid gland. However, because ct has a certain amount of radiation, frequent cervical ct examinations may be harmful to the cells of the pharynx, thyroid and other organs. In addition, if the enhancement ct is done, because the contrast agent is iodine contrast agent, although the dose is not large, but it may still have an impact on the thyroid function, especially if the patient himself originally suffers from a functional thyroid disease, such as hyperthyroidism, the impact is relatively large. Patients are advised to consult the contraindications of the test program in advance before doing the test.