Mixed occupancy in the left lobe of the thyroid gland means that there is abnormal tissue in the left lobe of the thyroid gland occupying the normal tissues of the thyroid gland, which may be thyroid cancer, benign thyroid nodule, or high-functioning adenoma of the thyroid gland. Thyroid cancer should be surgically removed; benign thyroid nodules can be observed with regular ultrasound rechecks; and high-functioning adenomas of the thyroid gland require surgical treatment. 1. Thyroid cancer: if the ultrasound of thyroid gland shows that the margin of thyroid occupation is not neat, rich in blood supply, accompanied by tiny calcification and enlarged lymph nodes in the neck, the possibility of malignancy of the occupation is high, and it is recommended that fine needle aspiration biopsy is performed to clarify the benignity and malignancy. If malignancy is confirmed, surgical resection is needed. 2. Benign thyroid nodules: if thyroid ultrasound shows that the thyroid occupations do not have malignant features such as irregular margins, abundant blood vessels, and tiny calcifications, then the possibility of benign nodules is high, and the patient can be observed for the time being, and can be rechecked on a regular basis. If the above features are present, but the fine needle aspiration shows benign occupancy, it can also be observed temporarily. 3. Thyroid hyperfunctioning adenoma: the thyroid gland produces a nodule that can secrete thyroid hormone independently, resulting in hyperthyroidism, which cannot be controlled by antithyroid medication alone and needs to be surgically removed. Patients with mixed occupancy of the left lobe of the thyroid gland should go to the hospital and be treated under the guidance of a doctor.