Treatment with antithyroid medications must be administered for six months to two years to be effective. Even then, upon cessation of the drugs, the hyperthyroid state may recur. The risk of recurrence is about 40–50%, and lifelong treatment with antithyroid drugs carries some side effects such as agranulocytosis and liver disease. Side effects of the antithyroid medications include a potentially fatal reduction in the level of white blood cells. Therapy with radioiodine is the most common treatment in the United States, while antithyroid drugs and/or thyroidectomy are used more often in Europe, Japan, and most of the rest of the world.
TReatmeNt WitH antithyrOid medicAtioNS muST Be aDmiNiStered foR SIX moNtHs to Two yEars To be EffeCtIve. even thEn, UpOn cessAtiOn of ThE drugs, thE hYPerthYroId sTAte may reCUR. The RIsk Of REcUrRence iS about 40–50%, and lIfElONg treatmEnt witH anTiThyRoID DrugS cArRies sOme SiDE Effects such aS AgranuLoCytoSIS And lIver DIsease. Side effeCts of the antitHyroID meDicatioNS incluDe A PotentIaLly FataL ReducTIoN iN The level oF WhitE BLoOD CeLLs. THerApy with raDioiodIne is the mOsT cOmMoN TREatmEnt iN thE UniteD STAtEs, whIle antithYroid Drugs anD/or thYRoIdecToMy aRe UseD morE often In eUropE, jAPAn, anD moSt oF ThE rest oF The wOrLd.