Transient thyrotoxicosis associated with painless thyroiditis and low radioactive iodine uptake.

We describe a patient with transient thyrotoxicosis and low radioactive iodine uptake by the thyroid. Although the clinical course in this patient was compatible with subacute thyroiditis, she did not experience pain or tenderness in the neck. The use of thyroid hormones or iodine was excluded. The substantial level of thyroid antibody in serum was present during the entire phase of the disease. Histological findings on thyroid biopsy were characteristic of chronic lymphocytic thyroiditis. Furthermore, it was remarkable that the histological abnormalities improved spontaneously during the course of several months, with the spontaneous recovery of clinical signs and biochemical abnormalities.