Effective Iodide Therapy for Untreated Patients With Graves' Hyperthyroidism Avoiding Thionamide Drugs With Many Side Effects
Condition: Graves Disease
MeSH terms: Graves Disease; Hyperthyroidism
Study type: Observational

Summary: 
      As the drug treatment of Graves' hyperthyroidism, Plummer reported the effectiveness of
      excess iodide in 1923 and iodide was used as the therapy for Graves' hyperthyroidism starting
      from the 1930s. After the introduction of more potent antithyroid drug, thionamide, most
      thyroidologists preferred to use thionamide expecting potent antithyroid effect, but some
      careful thyroidologists continued to prescribe iodide in mild type Graves' hyperthyroidism.
      Recently, American and Europe Thyroid Association recommended methylmercaptoimidazole (MMI),
      one of the potent thionamide drugs, as the first-choice drug for Graves' hyperthyroidism.
      However, it became apparent that thionamide has serious side effects such as not only
      agranulocytosis, but also severe liver injury, MPO-ANCA related vasculitis and embryopathy in
      the pregnant women. In Japan, one patient died of thionamide-induced agranulocytosis every
      year. The incidence of side effects including minor side effect of drug eruption is more than
      10%. We used to treat the patients with Graves' hyperthyroidism with MMI, as we reported in J
      Clin Endocrinol Metab 65:719, 1987. However, many side effects of thionamide prompted us to
      revive the treatment with classical KI in our outpatient clinic and found that KI was
      effective in the patients who showed side effects to thionamide, resulting in remission
      (reported in J Clin Endocrinol Metab 99:3995, 2014). Therefore, we began to treat the
      patients without serious complications such as heart failure or arrhythmia, with 100mg KI
      since 1996 and followed for 180 days. We were surprised to find that serum thyroid hormone
      level decreased in all the patients. Thionamide drugs were added only when euthyroidism could
      not be achieved by KI alone. Compared with thionamide, side effect of KI was almost none.
      Between 1996 and 2004, about 504 patients were treated with KI and a third of the patients
      were successfully treated with KI alone and other patients were also successfully treated
      with the combination of KI and thionamide, suggesting additive effect, or by radioactive
      iodine therapy. The long term prognosis of the patients initially treated with KI was almost
      the same as the patients initially treated with MMI. Our clinical experience suggested that
      patients with Graves' hyperthyroidism are also susceptible to excess iodide, as in the cases
      with Hashimoto thyroiditis, and this suppressive effect of excess iodide on the thyroid gland
      is a useful information for many patients suffering from Graves' hyperthyroidism and
      thionamide side effects.
    


Intervention name(s): Potassium Iodide
Intervention type(s): Drug
Observational model: Case-Only
Time perspective: Retrospective
Sampling method: Probability Sample
Study population: 
        primary care clinic