This is mainly caused by a decrease in the function of the parathyroid glands, which regulate calcium and phosphorus metabolism in patients. Each person has four parathyroid glands, which are located immediately behind the thyroid gland and depend on branches of the thyroid blood vessels for their nutrition. However, during thyroid surgery, the blood supply to the parathyroid glands is affected or the return of blood to the parathyroid glands is obstructed because the blood vessels associated with the thyroid glands must be cut, which affects the function of the parathyroid glands and causes numbness in the hands and feet. This condition may occur especially when the thyroid nodule is large or when cervical lymphatic drainage is performed. It is often relieved clinically by appropriate calcium supplements such as Calcium D tablets. This phenomenon will gradually disappear about 2 months after surgery as the blood supply is restored or the bruising subsides.