Occurrence and Hyperthyroidism Spontaneous Preceded by Remission of Graves' Painless Thyroiditis

A 45-year-old woman was referred to our hospital because of discomfort in the cervical region. Laboratory findings revealed thyrotoxicosis with positive TSH receptor antibodies, but acute inflammatory data were absent. After three weeks the thyroid hormone levels spontaneously decreased to hypothyroid levels, and thyroidal radioactive iodine uptake (RAID) was below normal. A needlebiopsy specimen of the thyroid gland obtained two months later showed diffuse lymphocytic thyroiditis, and she was therefore diagnosed as having had painless thyroiditis. Two months after returning to euthyroidism, a second thyrotoxicosis developed. TSH receptor antibodies remained positive, but RAIU was slightly above normal, indicating Graves' hyperthyroidism. Treatment with antithyroidal drugs was commenced but was soon discontinued due to an allergic reaction. Although only f3-adrenergic antagonist was administered for treating the thyrotoxicosis, thyroid function was gradually normalized in parallel with the reduction in TSH receptor antibody. In this case, painless thyroiditis would be followed by Graves' disease and subsequent spontaneous remission.