[Causes of congenital hypothyroidism. The Thyroid Study Group].

Congenital hypothyroidism (CHT) covers a heterogeneous group of disorders. In order to describe the causes of this group of diseases, we develop and make use of new methods. In this way we are able to give better genetic and therapeutic advices. These methods include ultrasonography, measurement of the urinary excretion of iodinated material and of thyroglobulin (Tg) and abnormal iodoprotein concentrations in serum. We studied about one third (63 children) of the hypothyroid newborns in the Dutch national screening program (1981-1984). 39% of the disorders was caused by thyroid dysgenesis, 41% by inborn errors of the thyroid gland metabolism (16% Tg synthesis disorders), 6% by iodine deficiency and 14% by amniofoetography. With the aid of polymorphisms in and around the Tg-gene we investigate the mode of inheritance of Tg-synthesis disorders. Moreover we study possibilities for prenatal diagnosis, with the aim to treat newborns directly after or if possible before birth.