[A case of Plummer disease that appeared in older old age after 10-year course of subclinical hyperthyroidism]

A 81-year-old woman with a thyroid tumor and subclinical hyperthyroidism since ten years ago was admitted to our hospital for palpitations and hyperthyroidism (FT(4) 1.75 ng/dl, FT(3) 5.37 pg/ml, TSH<0.03 microIU/ml). Although thyroid stimulating antibody (TSAb) was transiently and mildly positive, anti-TSH receptor antibody (TRAb), microsome test, and thyroid test were negative. Thyroid echogram showed an isoechoic nodule in the left lobe (33 x 42 x 22 mm) and a small nodule (10 x 15 x 9 mm) in right lobe. Thyroid scintiscan showed a hyperfunctional (hot) nodule in left thyroid lobe with suppressed uptake in the remainder of the gland. The uptake rate of thyroidal radioiodine ((123)I) in 24 hours was within the normal range (7.3%). Based on the above findings, a diagnosis of Plummer disease was made. Since she refused invasive surgical or radioiodine treatment, she was treated with 10 mg thiamazole daily. After treatment with propranolol and thiamazole, the thyrotoxic symptoms disappeared and thyroid function returned to normal level. She had osteoporosis but she had neither atrial fibrillation nor cardiac symptoms. This was a rare case of Plummer disease that appeared in extremely old age after a long course of subclinical hyperthyroidism.