Under normal circumstances, after thyroid surgery will not become thin, some patients just after surgery due to the inability to eat and drink normally, will make the body water loss and nutrient absorption will be reduced, there will be a temporary weight loss, but after resumption of eating and drinking will quickly return to normal, will not cause the body to become thin for a long time. If thinness is abnormal after thyroid surgery, on the one hand, there is a possibility that hyperthyroidism occurs after thyroid surgery, which enhances the metabolism of tissue cells and causes excessive consumption of nutrients; on the other hand, there is a possibility of malignant thyroid disease, which does not eliminate the cancerous cells completely after the surgery, and requires further radiotherapy or chemotherapy, which is more damaging to the body and causes nutritional problems. On the other hand, there may be malignant thyroid disease, in which the cancer cells have not been completely eliminated after surgery, and further radiation therapy or chemical drug treatment is needed, which will cause more damage to the body and result in poor absorption and utilization of nutrients, thus making the patient thin.