title: A randomized trial evaluating a block-replacement regimen during radioiodine therapy.
abstract: BACKGROUND
  Lack of consensus regarding the antithyroid drug regimen in relation to radioiodine ((131) I) therapy of hyperthyroidism prompted this randomized trial comparing two strategies.
  
  
  METHODS
  Patients with Graves' disease (GD, n = 51) or toxic nodular goitre (TNG, n = 49) were randomized to (131) I either 8 days following discontinuation of methimazole (-BRT, n = 52, median dose: 5 mg) or while on a continuous block-replacement regimen (+BRT, n = 48, median dose 15 mg methimazole and 100 μg levothyroxine). results: Patients in the +BRT group required more radioactivity. In this group, thyroid function did not change in the early post (131) I period, while serum-free T3 index was higher in the -BRT group (P < 0·05). One year posttherapy, the fraction of cured patients (euthyroid or hypothyroid) was 48% and 61% in the +BRT and -BRT group, respectively (P = 0·014 unadjusted; P = 0·004 adjusted), but the outcome depended on the type of disease. In GD, treatment failure in the +BRT group correlated positively with the 24-h thyroid (131) I uptake (P = 0·017), while no correlations existed in the -BRT group. In addition to +BRT allocation, patients with TNG were at higher risk of treatment failure with lower thyroid radiation doses (P = 0·048), higher doses of methimazole (P = 0·026) and lower levels of serum TSH (P = 0·009).
  
  
  CONCLUSIONS
  A continuous block-replacement regimen results in a stable thyroid function during (131) I therapy but is hampered by the higher amounts of radioactivity required. The study demonstrates that the outcome in GD is highly unpredictable, while treatment failure in patients with TNG is correlated with a number of factors.
authors.affiliation: Department of Endocrinology, Odense University Hospital, Denmark. steen.bonnema@dadlnet.dk
authors.forename: Steen J
authors.initials: SJ
authors.lastname: Bonnema
authors.forename: Peter
authors.initials: P
authors.lastname: Grupe
authors.forename: Henrik
authors.initials: H
authors.lastname: Boel-Jørgensen
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Brix
authors.forename: Laszlo
authors.initials: L
authors.lastname: Hegedüs
mesh_terms: D000328:Adult; D000368:Aged; D013956:Antithyroid Agents / Q000008:administration & dosage*; D003131:Combined Modality Therapy; D004334:Drug Administration Schedule; D005260:Female; D006044:Goiter, Nodular / Q000097:blood / Q000188:drug therapy / Q000532:radiotherapy; D006111:Graves Disease / Q000097:blood / Q000188:drug therapy / Q000532:radiotherapy; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000188:drug therapy* / Q000532:radiotherapy; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008713:Methimazole / Q000008:administration & dosage; D008875:Middle Aged; D011879:Radiotherapy Dosage; D013963:Thyroid Hormones / Q000097:blood; D013974:Thyroxine / Q000008:administration & dosage; D016896:Treatment Outcome
chemical_list: D013956:Antithyroid Agents; D007457:Iodine Radioisotopes; D013963:Thyroid Hormones; D008713:Methimazole; D013974:Thyroxine