FAMILIAL THYROXINE‐BINDING GLOBULIN DEFICIENCY

Abstract

Abstract. Three Danish pedigrees have been studied with a view to reduced thyroxine‐binding globulin (TBG). The study confirmed that this defect is transmitted by X‐chromosome‐linked dominant inheritance, there being no man‐to‐man transmission, but also that it may occur in two types: deficient TBG and low, non‐zero TBG. Definite changes of TBG and thyroid function tests were found in the hemizygous men, whereas the heterozygous women showed a marked variation in the range between the values for hemizygous men and normal persons. Determination of total thyroxine appears to afford more guidance than the protein‐bound iodine suggested by others. Two of four women on oral contraception exhibited such deviating TBG values that they are assumed to be TBG heterozygous. In all persons free thyroxine proved normal or slightly reduced but all the persons tested were euthyroid. However, the propositus of one family had previously been treated for Graves' disease.