[Two cases of familial thyroxine-binding globulin (TBG) deficit identified by the screening of neonatal hypothyroidism (author's transl)].

Thyroxine-binding globulin deficiency is a well-known condition transmitted as a X-linked dominant trait or as autosomal dominant trait. This condition is benign and hypothyroidism is never associated. Values of T4 in the serum are abnormally low, TSH values are normal, RT3U values are high. TBG deficiency probably are much more diffuse than we believed in past. Therefore it's possible to detect this deficit through screening programs for neonatal hypothyroidism. In this paper we describe two cases of TBG deficit. Thyroid function and TBG levels in babies and in their families are studied. In our sample of three years the incidence is I:3170 newborns, The presumable inheritance pattern are both X-linked dominant and autosomal dominant. Neither in affected babies nor in their relatives thyroid function is abnormal.