title: Factors influencing the success of radioiodine therapy in patients with Graves' disease.
abstract: OBJECTIVE
  The first dose of radioiodine (I) does not always cure hyperthyroidism in patients with Graves' disease (GD). Our aim was to evaluate the factors influencing the success of I therapy.
  
  
  METHODS
  We reviewed the medical records of 724 patients who were first diagnosed with GD between 2005 and 2009 and were subsequently treated with I in a fixed-dose manner considering the thyroid volume (TV). TSH, fT(4), and fT(3) were measured. TV was measured by means of ultrasonography. Successful therapy was followed by euthyroidism or hypothyroidism.
  
  
  RESULTS
  Out of 724 patients, 656 (90.5%) were successfully (Group 1) and 69 (9.5%) were unsuccessfully (Group 2) treated with the first dose of (131)I. In Group 1, the applied dose of (131)I was lower than that in Group 2 [626±107, 95% confidence interval (CI) 618-634, and 709±140, 95% CI 675-742 MBq, respectively; P<0.001]. At presentation, patients in Group 1 were younger than those in Group 2 (45.5±14.9, 95% CI 44.4-46.6, and 50.1±15.8, 95% CI 46.3-53.9 years, respectively; P=0.031). They had a lower fT(4) (54.9±26.1, 95% CI 52.9-56.9, and 72.1±34.1, 95% CI 63.9-80.3 pmol/l, respectively; P<0.001), a lower fT3 (20.9±8.2, 95% CI 20.3-21.5, and 23.9±8.2, 95% CI 21.9-25.9 pmol/l, respectively; P<0.001), and a smaller TV (21.5±13.2, 95% CI 20.2-22.8, and 35.6±22.3, 95% CI 28.2-42.9 ml, respectively; P<0.001). Before I therapy, patients in Group 1 had a lower fT(3) (9.6±6.0, 95% CI 9.2-10.1, and 11.3±7.6, 95% CI 9.5-13.2 pmol/l, respectively; P=0.038).
  
  
  CONCLUSIONS
  Successfully treated GD patients were younger, less severely hyperthyroid, and had a smaller TV at presentation. They were also less severely hyperthyroid before I therapy.
authors.affiliation: aDepartment of Nuclear Medicine, University Medical Centre Ljubljana bUniversity Eye Hospital, University Medical Centre Ljubljana cFaculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
authors.forename: Daša
authors.initials: D
authors.lastname: Šfiligoj
authors.forename: Simona
authors.initials: S
authors.lastname: Gaberšček
authors.forename: Polona Jaki
authors.initials: PJ
authors.lastname: Mekjavič
authors.forename: Edvard
authors.initials: E
authors.lastname: Pirnat
authors.forename: Katja
authors.initials: K
authors.lastname: Zaletel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006111:Graves Disease / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009929:Organ Size / Q000528:radiation effects; D012189:Retrospective Studies; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D016896:Treatment Outcome; D014463:Ultrasonography; D055815:Young Adult
chemical_list: D007457:Iodine Radioisotopes