Thyroid disorder is a common disease. Graves' disease is the most frequent cause of thyrotoxicosis and pharmacological treatment is current trends worldwide. Because of the severe adverse effects of propylthiouracil, methimazole or carbimazole should be selected as the drug of choice except for special situations such as women in the first trimester of pregnancy, thyroid storm, or in patients with severe side effects to methimazole. Treatment should continue for 12 to 18 months, but duration can be adjusted depending on the patient. For hypothyroidism, synthetic levothyroxine is the mainstay of treatment. In order to avoid overtreatment, the dosage of levothyroxine should be determined in consideration of the patient's age, sex, bodyweight, general condition, and comorbidities. In subclinical hypothyroidism, thyroid hormone replacement is suggested in patients with thyroid stimulating hormone concentrations >10 mIU/L. For non-elderly patients with high titers of thyroid autoantibodies, patients with dyslipidemia, pregnant patients, and women with infertility or ovulatory dysfunction, treatment with levothyroxine can be considered.