Value of the determination of "true' free thyroxine in screening the newborn with possible congenital TBG-deficiency for congenital hypothyroidism.

The results of investigation on a family after a screening programme for congenital hypothyroidism are presented. The newborn child and her father appeared to have a congenital thyroxine binding globulin deficiency. Problem regarding standard thyroid hormone tests are discussed. It was observed that the free T4 index as well as a commercial free T4 determination introduced earlier can give misleading results. The first experience with another more promising free T4 determination is also presented.