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X-Chromosome Linked Inheritance of Thyroxine-Binding Globulin Deficiency¹

Marshfield Clinic and Foundation, Marshfield, Wisconsin, and Metabolic Research Laboratory, V.A. Hospital, Minneapolis, and Department of Biochemistry, University of Minnesota Minneapolis, Minnesota

We have presented evidence for the inheritance of absent or reduced thyroxine binding globulin (TBG) capacity as a co-dominant, sex-linked trait (J Clin Endocr 26: 835, 1966). The study of a second unrelated family with this defect has yielded additional evidence that the trait is transmitted by x-chromosome linked dominant inheritance. The 8 male members of the present 3-generation kindred had no detectable TBG binding activity for either thyroxine or triiodothyronine. The 13 presumably heterozygous females had binding activity varying from very low to normal but always present. This pedigree contains normal male children of affected fathers, not demonstrated in the previous study. Thyroxine half-life studies in affected males gave times of 3.8 days as compared to the normal of 6–8 days. However, the daily thyroxine degradation rate was normal. Estrogen treatment of affected males did not elicit detectable TBG activity, whereas heterozygous females responded to treatment with increases in activity. No evidence for clinical disease or congenital abnormality associated with TBG deficiency has become manifest.

Supported in part by USPHS Grant CA-05993, and the V. A. Cooperative Urological Research Project.

¹ Portions of this data were presented at The Endocrine Society Meetings in Chicago, June 1966, and at the International Congress of Human Genetics, Chicago, September 1966.

Received March 1, 1967.

Accepted July 13, 1967.