The Role Of I-123 Imaging In The Evaluation Of Infants With Mild Congenital Hypothyroidism

Background/Aims: Controversy exists regarding the diagnosis and treatment of mild congenital hypothyroidism (MCH). We studied the value of I-123 imaging in patients with MCH. Methods: Retrospective chart review of infants and children <4 years of age who underwent I-123 imaging: group 1 = MCH [thyroid-stimulating hormone (TSH) < 25 mu IU/ml, normal free T-4/T-3], group 2 = severe congenital hypothyroidism (TSH = 25 mu IU/ml), and group 3 = MCH in infancy imaged after treatment withdrawal at age 3 years. Data collected included 4- and 24-hour I-123 uptake, TSH, free T-4/total T-3 at imaging, age at imaging, and levothyroxine (L-T-4) dose at 1 year of. Results: Thirty-six patients underwent I-123 imaging. In group 1 (n = 20, median TSH: 8.49 mu IU/ml), 85% had abnormal imaging consistent with dyshormonogenesis. Two patients were referred after 1 year of age. The median age at imaging for the remaining 18 patients was 54 days. Median L-T-4 dose at 1 year of age for these 18 patients was 2.8 mu g/kg, which is consistent with dyshormonogenesis. Ninety-one percent of group 2 (n = 11, median TSH: 428.03 mu IU/ml) had abnormal imaging. The median age at imaging was 13 days. Four patients in group 3 had abnormal I-123 imaging and restarted treatment. Conclusion: I-123 imaging is a valuable tool for evaluation, diagnosis, and treatment of MCH. (C) 2014 S. Karger AG, Basel