Peptide-linked iodotyrosines and iodothyronines in the blood of a patient with congenital goiter.

Abstract

A case of congenital goitrous hypothyroidism is reported. Studies were made to determine whether a metabolic defect was present. Intravenously administered I131-labeled diiodotyrosine and thyroxine were metabolized normally. Electrophoresis of plasma proteins after in vitro addition of I131-labeled thyroxine demonstrated normal amounts of thyroxine-binding protein. I131 was rapidly concentrated by the gland, and administration of potassium thiocyanate did not cause the release of trapped iodide. Endogenously labeled material in the serum was 60–65 per cent insoluble in butanol. The soluble fraction proved to be thyroxine and triiodothyronine. Starch-block electrophoresis and ultracentrifugation identified the butanol-insoluble portion as an abnormal iodinated protein having the mobility of albumin. This protein was not precipitated by equine anti-human serum albumin. After enzymatic hydrolysis of plasma, mono- and diiodotyrosine, thyroxine, and triiodothyronine were identified on paper chromatograms. This...