Thyroidectomy is primarily indicated for patients diagnosed with thyroid cancer, which includes various types such as papillary, follicular, medullary, and anaplastic thyroid cancer. The decision to proceed with surgery depends on factors such as the type and stage of cancer, the size of the tumor, its location, and whether it has spread to nearby tissues or lymph nodes. It is generally considered when the cancer poses a threat to surrounding structures or when there is a risk of metastasis.