Familial dysalbuminemic hypertriiodothyroninemia in a Japanese kindred.

A 56-year-old Japanese housewife had been diagnosed as having Graves' disease and was treated with methimazole. When she was referred to our hospital, the serum T3 level was high irrespective of high TSH level. High serum T3 levels were also observed in two out of her three sisters. Electrophoresis revealed that binding of 125I-T3 to serum albumin was markedly increased whereas the binding of 125I-T4 to serum albumin was slightly increased in the three sisters whose serum T3 levels were high. These data indicate that the presence of an albumin variant is the cause of hypertriiodothyroninemia in this family.