Familial thyroxine-binding globulin deficiency detected in a pilot screening program for congenital hypothyroidism.

During a pilot screening program for congenital hypothyroidism, performed in Italy over a three years period on 38,000 newborns, seven cases (1/5,400) of thyroxine-binding globulin (TBG) deficiency, have been detected. None of these infants was affected by any pathology or had been treated with drugs which could explain TBG deficiency as an acquired condition. Familial studies pointed out that the transmission of the defect is consistent or compatible with X-chromosome linkage.