***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: BACKGROUND In China , use of radioiodine therapy is problematic because of the need for lifelong levothyroxine substitution . Our aim was to find an optimum dosing strategy for (131)I treatment of hyperthyroidism due to Graves ' disease ( GD ) . We attempted to achieve euthyroidism to avoid long-term levothyroxine treatment . METHODS Six hundred patients with GD were r and omized into five groups , each comprising 120 individuals , to receive an individual (131)I activity selected from five different ascending activity ranges . The ranges were modulated according to a clinical score system . Follow-up was extended over a 12-year time frame . The primary outcomes were euthyroidism , hyperthyroidism , hypothyroidism , and recurrent hyperthyroidism . The secondary endpoint was the accumulated (131)I activity needed to achieve euthyroidism . RESULTS Out of 682 screened patients , 600 entered the study in 1997 . Five hundred twenty-nine completed the last follow-up visit at the end of the study in 2009 . Group 3 was identified as the study arm that received the optimum radioiodine activity , with 71.8 % of the patients maintaining a euthyroid status , 5.8 % remaining hyperthyroid , and 22.3 % becoming hypothyroid by the end of the study . This group received 1.85 - 4.07 MBq per gram of thyroid tissue ( average administered activity 261 ± 162 MBq ) . Over the 12-year follow-up period , the recurrence rate was 13.6 % . The efficacy  of (131)I treatment was related to activities modulated by a clinical score ( χ(2 ) = 82.1 , p = 0.000 ) . CONCLUSION Our protocol effectively treated hyperthyroidism and significantly reduced the hypothyroidism rate . It may be preferable to the intentional induction of permanent hypothyroidism recommended by many experts In order to assess the effect of propylthiouracil ( PTU ) or methimazole ( MMI ) pretreatment on patient outcome after radioiodine therapy , we examined 100 patients with Graves ' disease 3 , 6 , 9 , and 12 months after administration of a 10-mCi st and ard single dose of 131I .  They were assigned to one of three groups : no drug ( ND ) treatment ( 30 cases ) ; MMI ( 45 cases ) ; and PTU ( 25 cases ) . Antithyroid drugs ( ATD ) were withdrawn 15 days before radioiodine administration . The groups were similar concerning age , gender , ATD pretreatment duration , goiter size , and initial serum triiodothyronine ( T3 ) , thyroxine ( T4 ) , free thyroxine ( FT4 ) , antithyroid autoantibody levels , 24-hour radioiodine uptake and 131I dose administered per gram of thyroid tissue . ND and MMI groups presented a similar rate of cure of 73.3 % and 77.8 % respectively ( p = NS ) . In contrast , the PTU group showed a rate of cure of only 32 % ( p < 0.05 ) . Logistic regression analysis indicated that  PTU administration ( p = 0.003 ) and thyroid size ( p = 0.02 ) were the variables related to radioiodine therapy failure . Our data demonstrate that the chance of 131I treatment failure is higher in individuals using PTU than in patients using MMI or not using any ATD before radioiodine ( odds ratio [ OR ] 5.84 ; 95 % confidence interval [ CI ] 1.82 - 18.76 ) suggesting that PTU should be avoided in the treatment of patients with Graves ' disease Purpose Graves ’ disease is the most frequent cause of hyperthyroidism . Although treatment with antithyroid drugs or radioactive iodine is effective , surgery remains the preferred treatment for many patients . We analyzed the results of 55 prospect ively followed patients who underwent total thyroidectomy for Graves ’ disease . Methods Total thyroidectomy was performed by experienced endocrine surgeons in all 55 patients . We monitored the patients postoperatively for early and late complications . Results There were 19 men , with a mean age of 42 years ( range , 34–68 years ) and 36 women , with a mean age of 38 years ( range , 19–78 years ) . One patient suffered postoperative hemorrhage and subsequent wound infection , two patients had transient recurrent laryngeal nerve palsy , and 24 patients had transient hypocalcemia . The mean follow-up time was 4 years ( range , 10 months to 6 years ) . Recurrence of hyperthyroidism was not reported in this period . Conclusion Removal of all thyroid tissue offers the best chance of preventing recurrent hyperthyroidism .  Total thyroidectomy is the most effective surgery for achieving the goal of treatment of Graves ’ disease to ensure that hyperthyroidism will not recur The optimal method for determining iodine-131 treatment doses for Graves ' hyperthyroidism is unknown , and techniques have varied from a fixed dose to more elaborate calculations based upon gl and size , iodine uptake , and iodine turnover . Patients with Graves ' hyperthyroidism ( n = 88 ) who had not been previously treated with radioactive iodine  were r and omized to one of four dose calculation methods : low-fixed , 235 MBq ; high-fixed , 350 MBq ; low-adjusted , 2.96 MBq ( 80 micro Ci)/g thyroid adjusted for 24 h radioiodine uptake ; and high-adjusted , 4.44 MBq ( 120 micro Ci)/g thyroid adjusted for 24 h radioiodine uptake . Subjects were followed for mean of 63 months ( range , 10 - 94 months ) for the following clinical outcomes : euthyroid without medication , hyperthyroid requiring further radioiodine , and hypothyroid requiring life-long L-T(4 ) . Mean treatment doses were similar in the different outcome groups . We could not demonstrate any advantage to using an adjusted dose method . Survival analysis did not demonstrate any difference in the time to outcome between the fixed and adjusted dose methods . The use of a fixed dose method simplifies the approach to treatment with potential cost savings AIM Despite extensive use of (131)I therapy for Graves ' hyperthyroidism the treatment regimen with (131)I and antithyroid drugs remain under discussion . In our prospect i ve clinical study we followed acute thyroid hormone changes after (131)I in patients not pretreated with methimazole ( MMI ) and in patients with different MMI pretreatment regimens . PATIENTS , METHODS 187 patients were treated with fixed activity of 550 or 740 MBq of (131)I. First group ( 71 patients ) received (131)I alone . In the second group ( 57 patients ) MMI was stopped seven days before (131)I. The third group ( 59 patients ) received MMI until (131)I application .  Initial free triiodothyronin and free thyroxin were measured in the second group 7 and 2 days before (131)I therapy and in all three groups on the day of (131)I application as well as 2 , 5 , 12 , and 30 days afterwards . Absorbed dose was measured in each patient . RESULTS In the non-pretreated group (131)I application was followed by a significant decrease of fT4 in 5 days and of fT3 in 2 days , higher reduction was detected in patients with higher baseline values . In MMI pretreated patients significant but clinical ly irrelevant increase of both thyroid hormones was detected with maximum value 7 days after discontinuation in the second group and 5 days after discontinuation in the third group . Additionally , in patients of the third group absorbed dose of (131)I was significantly lower relative to other two groups . We found no correlation between absorbed dose of (131)I and thyroid hormone changes . CONCLUSION Our study demonstrates that (131)I application alone does not result in exacerbation of hyperthyroidism and therefore it may be considered as safe . Additionally , MMI withdrawal causes significant but clinical ly irrelevant elevation of thyroid hormones CONTEXT Despite accounting for variations in gl and size and iodine kinetics , the success of radioiodine therapy in patients with Graves ' disease remains moderately common and unpredictable . OBJECTIVES We hypothesized that hypoechogenic gl and s , with large , densely packed cells , are more radiosensitive than normoechogenic gl and s , in which much radiation is wasted on more abundant colloid . We evaluated this hypothesis in a cohort of patients with Graves ' disease . DESIGN This was a prospect i ve trial of patients recruited during 4 yr and followed up 1 yr after radioiodine therapy .  SETTING This trial was held in a university hospital-outpatient clinic . PATIENTS A total of 177 consecutive patients with first presentation of Graves ' disease ( 28 males ) , 23 - 76 yr old , who relapsed after antithyroid therapy were included in the study . INTERVENTION The patients were assigned to an ablative target-absorbed dose of 200 Gy ( n = 78 ) or r and omly to 100 or 120 Gy of nonablative dose ( n = 99 ) . MAIN OUTCOME MEASURES The measures were incidences of hyperthyroidism , euthyroidism , and hypothyroidism at 12-month follow-up . RESULTS At follow-up there were 25 hyperthyroid , 44 euthyroid , and 108 hypothyroid patients . Compared with 96 patients with a hypoechogenic gl and , in 81 patients with a normoechogenic gl and , there were more hyperthyroid ( 22 vs. 7 % ) and euthyroid ( 41 vs. 11 % ) , but less hypothyroid outcomes ( 37 vs. 81 % ; P < 0.0001 ) . The other independent predictor of increased radioresistance was the large gl and volume . CONCLUSION In patients with Graves ' disease , normoechogenic and large gl and s are associated with increased radioresistance Purpose This study evaluated the thyroidal kinetics of radioiodine in Graves ’ disease under continued thiamazole medication and after discontinuation of thiamazole for 1–2 days , with a view to keeping the period of discontinuation as short as possible and to exploring the underlying mechanism of a postulated radioprotective effect of antithyroid drugs . Methods In 316 patients , diagnostic and therapeutic radioiodine kinetics were followed up for 2 days by ten uptake measurements each and were defined mathematically by a two-compartment model . Results Without thiamazole or when thiamazole was discontinued for at least 2 days , all uptake curves could be fitted perfectly by a simple in- and output function ; the mean square error ( mse ) was 0.38 ( test ) and 0.28 ( therapy ) . Under continued thiamazole medication ( 11.0±7.0 mg/day ) , the energy dose delivered to the thyroid was lowered by factor of 2.5 . Uptake curves were deformed ( mse : 1.06 , test and 0.86 , therapy ) and appeared two peaked , suggesting coexistence of follicles with blocked and follicles with intact hormone synthesis and hence heterogeneous radioiodine uptake in the thyroid . In patients with maximally altered uptake curves , the success rate was as low as 31 % . One day after discontinuation of thiamazole  , mse was still increased ( 0.78 , test ) , while 2 days afterwards it had normalised ( 0.36 , test ) and 3 days afterwards ( mse : 0.24 , therapy ) the success rate was 87 % . Conclusion Efficacy of radioiodine therapy under continued thiamazole medication is reduced not only by a lower uptake and shorter half-life of radioiodine , but also by a heterogeneous energy dose distribution in the thyroid . Discontinuation of thiamazole ( but probably not of propylthiouracil ) for at least 2 days is required to restore the efficacy of radioiodine Purpose Carbimazole ameliorates hyperthyroidism but reduces radioiodine uptake and adversely affects the outcome of simultaneous radioiodine therapy . We explored whether withdrawal of carbimazole for 3 days can restore the outcome of radioiodine treatment without concurrent exacerbation of hyperthyroidism . By generating three groups with comparable radioiodine uptake , we also investigated whether the effect of carbimazole depends on the radioiodine uptake . Methods Stratified by a radioiodine uptake > 30 % , 227 consecutive adult patients were prospect ively assigned to radioiodine therapy ( target dose 200 Gy ) without , on or 3 days off carbimazole . Patients were clinical ly ( Crooks-Wayne score ) and biochemically ( T3 , fT4 , TSH ) followed up after 3 , 6 and 12 months . Primary endpoint was outcome 12 months after radioiodine therapy . Results A total of 207 patients completed follow-up ( toxic nodular goitre , n=117 ; Graves ’ disease , n=90 ) . The overall success rate was 71.5 % . Patients without and 3 days off carbimazole had similar biochemical ( 81.4 % and 83.3 % , respectively ; p=0.82 ) and clinical outcomes [ median ( range ) Crooks-Wayne score 0 ( 0–16 ) and 1 ( 0–10 ) , respectively ; p=0.73 ] , 
    Output:
    
Conclusions On the basis of the outcomes analyzed , surgery appears to be the most successful in the management of GD , with TT being the preferred surgical option