Background. Riedel's thyroiditis is an often disabling disease with clinical and histologic similarity to several other fibrous inflammatory disorders. Surgical treatment alone is often unsatisfactory in permanently alleviating airway compression, dysphagia, neck immobility, pain, or chronic fatigue syndrome. Investigation of drugs shown to be of benefit in the treatment of related fibrous disorders in which hormonal factors or inflammatory deregulation appear to be important is indicated. Tamoxifen has not been previously used in the treatment of Riedel's thyroiditis. Methods. Four patients with clinical and histologic diagnoses of Riedel's thyroiditis were evaluated before and after treatment with tamoxifen. Each had progressive symptomatic disease of 3 to 16 years' duration despite one or more surgical procedures and steroid therapy. Subjective improvement was noted in all cases, and objective changes were confirmed by periodic physical and computed tomographic examinations. Results. Patients have been monitored for 1 to 4 years with subjective improvement in 100% and objective disease regression ranging from 50% to 100% in all patients. One patient had complete regression within 6 months, and another had more than 50% regression within 3 months. All have returned to predisease activity levels. There were no significant side effects of the therapy. Conclusions. Tamoxifen has proved to be the most effective drug therapy available for managing Riedel's thyroiditis. Our studies suggest that this is unrelated to antiestrogen activity. Tamoxifen's effectiveness may be caused by a mechanism by which it stimulates the release of transforming growth factor-β, which may inhibit the fibroblastic proliferation characteristic of Riedel's thyroiditis.
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