title: Would I-123 di-iodotyrosine provide a harmless deiodination test? Concise communication.
abstract: Defective iodotyrosine deiodinase activity may benefit from a specific treatment, thus requiring an unequivocal diagnosis. In reported cases this diagnosis has been obtained from an in vivo deiodination test making use of di-iodotyrosine (DIT) labeled either with I-131 or I-125. Dosimetric calculation indicates that such tests may result in unacceptable irradiation of the thyroid of a child wrongly suspected of having defective iodotyrosine deiodinase activity; therefore other methods are needed. The use of I-123 DIT is shown to be feasible, but even a 1:30 reduction in the thyroid dose still remains too high. Suppression of thyroid I- uptake by ClO4-, together with I-125 DIT, eliminates almost all thyroid irradiation and provides a sensitive, harmless, and rapid test.
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D004105:Diiodotyrosine; D005260:Female; D006801:Humans; D007223:Infant; D007453:Iodide Peroxidase / Q000172:deficiency* / Q000378:metabolism; D007457:Iodine Radioisotopes / Q000378:metabolism; D007553:Isotope Labeling / Q000379:methods; D008297:Male; D008875:Middle Aged; D010472:Perchlorates / Q000494:pharmacology; D010544:Peroxidases / Q000172:deficiency*; D011188:Potassium / Q000494:pharmacology; D017680:Potassium Compounds; D011829:Radiation Dosage; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism
chemical_list: D007457:Iodine Radioisotopes; D010472:Perchlorates; D017680:Potassium Compounds; C009006:potassium perchlorate; D004105:Diiodotyrosine; D010544:Peroxidases; D007453:Iodide Peroxidase; D011188:Potassium