Thyroid function and thyroid cancer are not necessarily related. It is possible to have thyroid cancer even when thyroid function is normal. Clinically, thyroid cancer is usually detected by color ultrasound. Clinicians will classify thyroid nodules based on their size, texture, growth direction, presence of blood flow signals, clarity of boundaries, infiltration of surrounding tissues, and enlargement of nearby lymph nodes. Nodules classified as categories one to three generally have a benign tendency, and regular follow-up appointments are sufficient. If the nodules are classified as categories four to five, they are suggestive of malignancy, and it is recommended to perform thyroid fine needle aspiration or surgery to determine the pathological type of the nodules.