Postpartum thyroiditis and familial dysalbuminemic hyperthyroxinemia

Familial dysalbuminemic hyperthyroxinemia (FDH) is a syndrome associated with euthyroidism and increased binding of T4 to serum albumin. The combined occurrence of FDH and postpartum hyperthyroidism due to Graves' disease has only been reported in one patient. We now describe the first case of FDH and thyrotoxicosis due to postpartum silent thyroiditis. In a 19-yr-old woman, FDH, suspected on the basis of strikingly elevated analog free T4 (fT4) and total T4 values, but normal two-step fT4 and serum TSH values, was confirmed by [125I]T4 agarose-gel electrophoresis. When FDH and thyrotoxicosis, characterized by markedly elevated analog fT4, total T4, and two-step fT4 values and undetectable TSH values, coexist, the differential diagnosis may be confusing.