Which of the following conditions is the most common complication of radioiodine treatment of Grave's disease-

*Radioactive iodine treatment destroys thyroid cells and reduces the mass of cell functioning tissue. *Radioactive iodine is generally used for adults over 40 years of age and contraindicated in pregnant and nursing mothers. Disadvantages are- 1.Chances of developing thyroid insufficiency and permanent myxoedema. 2.Requires some time to control the disease. 3.Nodules may develop into thyroid during this therapy 4.Not very satisfactory in cases of nodular toxic goiter. 5.Very high incidence of hypothyroidism as the years passes by. Advantages are- 1.Do not require a prolonged drug therapy or surgery. 2.Cheap in comparison to other available treatment modalities.