DEFECT OF THE IODINATING SYSTEM IN CONGENITAL GOITROUS CRETINISM: REPORT OF A CASE WITH BIOCHEMICAL STUDIES*

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Abstract
A study of a 15½-year-old male with goitrous cretinism is reported. The patient's thyroid gland concentrated I131 well but released the accumulated I131 following oral administration of thiocyanatc. Thyroid tissue obtained by thyroidectomy was homogenized and fractionated by differential ccntrifugation into 900×g and 40,000×g sediments. Each fraction was suspended in Krebs-Ringer bicarbonate buffer, pH 8.4, and incubated with I131 and iodide or I131, iodide and an H2O2-generating system. No monoiodotyrosine (MIT) was found on chromatograms of the enzymatically hydrolyzed incubation mixtures. Normal human thyroid tissue under the same conditions formed MIT, and the addition of an H2O2-generating system effected augmentation of MIT formation. Three possibilities are considered for the abnormal mechanism in the patient's thyroid gland: 1) an iodinase defect, 2) defective formation of “active” iodide, or 3) an abnormal receptor protein (thyroglobulin). The first possibility is favored in this case.

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