INTRODUCTION:Radioactive iodine(I131) therapy is an established definitive treatment for Graves' hyperthyroidism.However,the optimal method of determining the radioiodine treatment dose remains controversial.
OBJECTIVE: To compare the efficacy of fixed dose versus  calculated  dose  regimen  in  the  treatment  of  Graves'  hyperthyroidism  among  Filipinos 
METHODOLOGY: Diagnosed   Graves'   disease   patients underwent  thyroid  ultrasound  to  estimate  thyroid  size. Patients  were  randomized  to  either  fixed  or  calculated dose  of  radioiodine  treatment.  For  fixed  dose  group,the  WHO  goiter  grading  was  utilized:  Grade   0   (5mCi),  Grade   1  (7mCi),  Grade2  (10mCi),  Grade  3  (15mCi).  For calculated  dose  group  the  following  formula  was  used:
                    Dose(mCi)= 160uCi/g thyroid x thyroid gland weight in grams x 100  /  24-hour RAIU(%)
Thyroid function test (TSH,FT4)  was monitored every  three  months  for  one  year. 
RESULTS: Of  the  60  patients  enrolled,  45  (fixed  dose;  n= 27,  calculated  dose;  n=  18)  completed  the  six  months follow-up  study.  Analysis  was  done  by  application  of  the  intention-to-treat  principle.  The  percentage  failure  rate  at  third  month  in  the  fixed  vs.  calculated  dose  group  was:  26  v.  28%  with  a  relative  risk  (RR)  value  of  0.93.  At  six  months  post-therapy,  there  was  a  noted  reduction  in  the  failure  rates  for  both  study  groups  (11  vs.  22%,  respectively),  with   a   further   reduction   in   the   relative   risk   value (0.67),  favoring  the  fixed  dose  group.
CONCLUSION: Fixed   dose   radioiodine   therapy   for Graves'   disease   is   observed   to   have   a   lower   risk   of   treatment   failure   (persistent   hyperthyroidism)   at   three  and  six  months  post-therapy  compared  to  the calculated  dose.

Human ; Male ; Female ; Middle Aged ; Adult ; Iodine Radioisotopes ; Iodine ; Intention To Treat Analysis ; Graves Disease ; Hyperthyroidism ; Goiter ; Thyroid Function Tests ; Treatment Failure