FAMILIAL GOITRE WITH PARTIAL IODINE ORGANIFICATION DEFECT, LACK OF THYROGLOBULIN, AND HIGH LEVELS OF THYROID PEROXIDASE

SUMMARY From a sibship of three sisters having congenital goitre and normal hearing, two had impairment of organification of iodide. S 1 (4 years old) had goitre since birth, euthyroidism, and a negative perchlorate test. S 2 (15 years old) and S 3 (13 years old) were hypothyroid, and had radioiodide discharge after potassium perchlorate administration of 19.8% and 26.1%, respectively. Thyroid tissue was obtained at thyroidectomy. Peroxidase activity, in the thyroidal subcellular particles, was found to be qualitatively normal, but quantitatively increased. In the triiodide assay, the activity was: S 1 6912 u, S 2 2590 u, and S 3 3844 u (normal values 900‐1700 u). In the tyrosine‐iodinase assay, the activities, expressed as nmoles of iodide incorporation per gram of tissue, were S 1 1046, S 2 471, and S 3 547 (normal values 220‐410). The activity of the thyroidal NADPH‐cytochrome c reductase, an enzyme possible involved in hydrogen peroxide generation, was: S 1 0.084, S 2 0.047, and S 3 0.055 (normal values 0.018 μEq/min/mg). No thyroglobulin was detected by analytical ultracentrifugation, polyacrylamide gel electrophoresis, or double immunodiffusion in agar of the supernatant fractions. In patient S 3 , whose gland was labelled in vivo with 125 I, 60% of the total radioactivity of the gland (pooled nodular and paranodular specimens) was in a particulate iodoprotein that was solubilized by trypsin, deoxycholate or digitonin. In the soluble fraction there were two iodoproteins: iodoalbumin, and a second iodoprotein similar to the solubilized particulate iodoprotein. It is postulated that absence of the normal thyroidal receptor protein might be in some cases a cause of iodine organification defect.