Continuous methimazole therapy and its effect on the cure rate of hyperthyroidism using radioactive iodine: an evaluation by a randomized trial.
BACKGROUND
A randomized clinical trial was performed to clarify whether continuous use of methimazole (MTZ) during radioiodine ((131)I) therapy influences the final outcome of this therapy.


METHODS
Consecutive patients with Graves' disease (n = 30) or a toxic nodular goiter (n = 45) were rendered euthyroid by MTZ and randomized to stop MTZ 8 d before (131)I (-MTZ; n = 36) or to continue MTZ until 4 wk after (131)I (+MTZ; n = 39). Calculation of the (131)I activity included an assessment of the (131)I half-life and the thyroid volume.


RESULTS
The 24-h thyroid (131)I uptake was lower in the +MTZ group than in the -MTZ group (44.8 +/- 15.6% vs. 62.1 +/- 9.9%, respectively; P < 0.001). At 3 wk after therapy, no significant change in serum free T(4) index was observed in the +MTZ group (109 +/- 106 vs. 83 +/- 28 nmol/liter at baseline; P = 0.26), contrasting an increase in the -MTZ group (180 +/- 110 vs. 82 +/- 26 nmol/liter; P < 0.001). The number of cured patients was 17 (44%) and 22 (61%) in the +MTZ and -MTZ groups, respectively (P = 0.17). Cured patients tended to have a lower 24-h thyroid (131)I uptake (50.1 +/- 13.8% vs. 56.4 +/- 17.1%; P = 0.09). By adjusting for a possible interfactorial relationship through a regression analysis (variables: randomization, 24- and 96-h thyroid (131)I uptake, type and duration of disease, age, gender, presence of antithyroid peroxidase antibodies, thyroid volume, dose of MTZ), only the continuous use of MTZ correlated with treatment failure (P = 0.006), whereas a low 24-h thyroid (131)I uptake predicted a better outcome (P = 0.006).


CONCLUSIONS
Continuous use of MTZ hinders an excessive increase of the thyroid hormones during (131)I therapy of hyperthyroid diseases. However, such a strategy seems to reduce the final cure rate, although this adverse effect paradoxically is attenuated by the concomitant reduction of the thyroid (131)I uptake.
Bonnema
Steen Joop
SJ
Department of Endocrinology and Metabolism, Odense University Hospital, DK-5000 Odense C, Denmark. steen.bonnema@dadlnet.dk
Bennedbaek
Finn Noe
FN
Veje
Annegrete
A
Marving
Jens
J
Hegedüs
Laszlo
L
D000328:Adult; D000368:Aged; D013956:Antithyroid Agents / Q000008:administration & dosage*; D003131:Combined Modality Therapy; D005260:Female; D006044:Goiter, Nodular / Q000188:drug therapy / Q000532:radiotherapy; D006111:Graves Disease / Q000188:drug therapy / Q000532:radiotherapy; D006801:Humans; D006980:Hyperthyroidism / Q000188:drug therapy* / Q000532:radiotherapy*; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D016015:Logistic Models; D008297:Male; D008713:Methimazole / Q000008:administration & dosage* / Q000009:adverse effects; D008875:Middle Aged; D012008:Recurrence; D013972:Thyrotropin / Q000097:blood; D016896:Treatment Outcome
D013956:Antithyroid Agents; D007457:Iodine Radioisotopes; D008713:Methimazole; D013972:Thyrotropin