Block-replacement Therapy During Radioiodine Therapy
Condition: Toxic Nodular Goitre; Graves' Disease
MeSH terms: Graves Disease; Goiter; Goiter, Nodular
Study type: Interventional
Phase: Phase 4

Summary: 
      Background: The use of radioactive iodine (131I) therapy as the definite cure of
      hyperthyroidism is widespread. According to a survey on the management of Graves' disease,
      thirty per cent of physicians prefer to render their patients euthyroid by antithyroid drugs
      (ATD) prior to 131I therapy. This strategy is presumably chosen to avoid 131I induced
      'thyroid storm', which, however, is rarely encountered. Several studies have consistently
      shown that patients who are treated with ATD prior to 131I therapy have an increased risk of
      treatment failure. Mostly, patients with Graves' disease have been studied, while other
      studies were addressed also toxic nodular goiter. Thus, it is generally accepted that ATD
      have 'radioprotective' properties, although this view is almost exclusively based on
      retrospective data and is still under debate. Indeed, this dogma was recently challenged by
      two randomized trials in Graves' disease, none of which showed such an adverse effect of
      methimazole pretreatment. It cannot be excluded that the earlier results may have been under
      influence of selection bias, a source of error almost unavoidable in retrospective studies.
      Whether ATD is radioprotective also when used in the post 131I period has also been debated.
      In the early period 131I therapy following a transient rise in the thyroid hormones is seen
      which may give rise to discomfort in some patients. The continuous use of ATD during 131I
      therapy, possibly in combination with levothyroxine (BRT: block-replacement therapy), leads
      to more stable levels of the thyroid hormones. By resuming ATD following 131I therapy,
      euthyroidism can usually be maintained until the destructive effect of 131I ensues.
      Nevertheless, many physicians prefer not to resume ATD, probably due to reports supporting
      that such a strategy reduces the cure rate. Parallel to the issue of ATD pretreatment, the
      evidence is based on retrospective studies and the ideal set-up should be reconsidered. To
      underscore the importance of performing randomized trials we showed recently that resumption
      of methimazole seven days after 131I therapy had no influence on the final outcome.

      Aim:To clarify by a randomized trial whether BRT during radioiodine therapy of hyperthyroid
      patients influences the final outcome of this therapy, in a comparison with a regime in which
      methimazole as mono-therapy is discontinued 8 days before radioiodine.

      Patients and Methods: Consecutive patients suffering from recurrent Graves' disease (n=50) or
      a toxic nodular goiter (n=50) are included. All patients are rendered euthyroid by
      methimazole (MMI) and randomized either to stop MMI eight days before 131I or to be set on
      BRT. This latter medication continues until three months after 131I. Calculation of the 131I
      activity (max. 600 MBq) includes an assessment of the 131I half-life and the thyroid volume.
      Patients are followed for one year with close monitoring of the thyroid function.
    


Intervention name(s): MTZ+LT4; Methimazole
Intervention type(s): Drug; Drug
Intervention MeSH terms: Methimazole
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Radioiodine therapy; Graves' disease; toxic nodular goiter; antithyroid drugs; levothyroxine; radioprotection