Familial dysalbuminemic hyperthyroxinemia: a study of four probands and the kindred of three.

We investigated four probands, and the kindred of three, with familial dysalbuminemic hyperthyroxinemia, using the one- and two-step tests for free thyroxin and other thyroid-function tests. The results indicate that this is an autosomal dominant trait. The discovery of eight cases in our patient population, which represents about 4% of our hyperthyroxinemic patients (8/320), during eight months indicates that this aberration is more common than suspected. Its importance lies in the misinterpretation of test results and the consequent inappropriate treatment for thyrotoxicosis.