Prevention of Postoperative Hypocalcemia of Oral Vitamin D Supplementation Before Total Thyroidectomy

Inclusion Criteria: * Patients aged 19 to 70 years old * Patients undergoing total thyroidectomy due to thyroid disease * Patients who consented to the study and obtained consent for the study Exclusion Criteria: * Patients with confirmed hypocalcemia or hypercalcemia before surgery * Patients receiving calcium or vitamin D treatment before surgery, patients with excessive vitamin D * Patients with a previous history of parathyroid disease or a history of cervical irradiation * Patients with confirmed parathyroid comorbidity * Patients with diseases or conditions that cause hypercalcemia or hypercalciuria (myeloma, bone metastases, or other malignant bone diseases) * Patients with confirmed renal dysfunction (glomerular filtration rate \<60mL/min/1.73m2) before surgery or with a history of chronic renal failure * Renal stone disease patient, kidney stone disease patient * Patients with bowel disease that may affect serum vitamin D levels (celiac disease, small intestine resorption disease, small bowel resection history) * Patients taking drugs that may affect serum calcium or vitamin D levels (anticonvulsants, bisphosphonates, cisplatin, aminoglycosides, diuretics, proton pump inhibitors, glucocorticoid benzodiazepine derivatives, etc.) * Uncontrolled hypertension, diabetes, and clotting disorders * Cardiovascular disease (angina pectoris, heart failure, myocardial infarction, coronary artery disease, history of arrhythmia treatment, stroke, transient ischemic attack), and taking medications for arrhythmia * Drug Abuse and Alcohol Abuse * Patients who participated in other drug clinical trials within 30 days * Patients with a history of allergies to drugs * For women, pregnant and lactating patients * Patients judged unsuitable by the person in charge of the clinical trial * Patients with genetic problems such as galactose intolerance, lactose deficiency, or glucose-galactose malabsorption disorder