Retrospective Analysis of Infants Designated as Positive on Mass-Screening for Congenital Hypothyroidism at Kagoshima University

Mass-screening for congenital hypothyroidism has identified cases of mild hypothyroidism,transient hypothyroidism, and transient hyperthyrotropinemia as well as typicalhypothyroidism. In this paper, we examine the clinical data of the cases found positive inthe screening test at our hospital. From 1989 to 1999 there were 72 patients with positivescreening tests who started levothyroxine sodium (l-T4; Thyradin-S) as supplement therapy.At the age of 3 to 4 yr the patients were re-evaluated to determine whether treatmentshould be continued. Thyroid scintigraphies were done at the same time. We divided thesecases into 4 groups. Those in group 1A started l-T4 in early infancy without a TRH testbecause of obvious clinical evidence of hypothyroidism, and treatment was continued afterre-evaluation (n=37). Those in group 1B also started treatment in early infancy without aTRH test, but treatment was discontinued after re-evaluation (n=20). Patients in group 2Astarted l-T4 after evaluation by a TRH test and treatment was continued afterre-evaluation (n=14), while those in group 2B started treatment after a TRH test, butafter re-evaluation, treatment was discontinued (n=1). In group 2A, only a low dose ofl-T4 was needed, and a slightly elevated TSH and slightly decreased free T4 (FT4) wereobserved after the drug washout period. However, these patients had an exaggeratedresponse to the TRH test at re-evaluation. These findings indicate that this group,forming not a small part of whole screening-positive subjects, had mild hypothyroidism.Such patients require careful follow-up and repeated evaluation to determine whethertreatment should be continued.