The thyroid gland is the largest endocrine gland in the body and its main function is to synthesize thyroid hormones and regulate the body’s metabolism. Some thyroid disorders require surgery. Whether or not to take thyroxine after surgery is determined by the extent of thyroid removal and the volume and recovery of the remaining thyroid gland, so not all thyroid disorders require thyroxine after surgery. The cases that require post-operative euthyroxine to prevent hypothyroidism are as follows: 1. Since more than 2/3 of the thyroid gland has been removed during surgery, the secretion of thyroxine is greatly reduced and must be maintained by oral thyroxine treatment, otherwise symptoms of hypothyroidism will occur; 2. It is necessary to take Eugenol for life after thyroid cancer surgery to replenish the missing thyroxine on the one hand, and inhibit the recurrence of malignant tumor on the other.