The relationship between the method of the treatment of hyperthyroidism due to Graves' disease and the course of Graves' ophthalmopathy is debated. The investigators aimed to compare the results of total thyroidectomy done in 6 months following the appearance of the symptoms of ophthalmopathy and the antithyroid drug therapy in patients with moderate to severe Graves' ophthalmopathy.

The inclusion criteria: 1)Hyperthyroidism and moderate to severe Graves' ophthalmopathy within 6 months, 2)Thyroid volumes greater than or equal to 15 mL in thyroid ultrasonography, 3)Patients taking no treatment except local medications for Graves' ophthalmopathy, 4)Clinical activity score of 3/7 or more, proptosis greater than or equal to 21 mm in one eye or 2 mm difference between two eyes, presence of diplopia, the opening of the eye lid greater than or equal to 9 mm.

All patients will be treated with antithyroid drug until TSH levels of the patients are between 0.4-1. During this period all the patients will take pulse methyl prednisolone treatment of a total dose of 4.5 gr. After pulse steroid treatment the patients will be randomised to two groups: one group will be sent to surgery for total thyroidectomy, and their TSH levels will be kept between 0.4-1 with levothyroxine treatment; the other group will be followed under antithyroid drug treatment and their TSH levels will be kept between 0.4-1 also.

The smoking habits will be asked. Serum TSH, fT4 levels, Hertelmeter and eye lid opening measurements, clinical activity scores, diplopia will be evaluated monthly; TSH receptor antibody, anti-thyroid peroxidase and anti-thyroglobulin levels will be measured in 3 months intervals for a period of 12 months.

Inclusion Criteria:

• Hyperthyroidism and moderate to severe Graves' ophthalmopathy within 6 months,
• Thyroid volumes greater than or equal to 15 mL in thyroid ultrasonography,
• Patients taking no treatment except local medications for Graves' ophthalmopathy,
• Clinical activity score of 3/7 or more, proptosis greater than or equal to 21 mm in one eye or 2 mm difference between two eyes, presence of diplopia, the opening of the eye lid greater than or equal to 9 mm.

Exclusion Criteria:

• Patients taking treatment other than local medications for Graves' ophthalmopathy (eg: steroid treatment)