Predictors of Transient Hypothyroidism in Neonatal Screening Test / 대한소아내분비학회지

ABSTRACT

PURPOSE: Congenital hypothyroidism is detected through the neonatal screening test and treated early from neonatal period. Among these patients, however, transient hypothyroidism is included. In this study, we aimed to evaluate the predicting factors of transient hypothyroidism in neonatal screening test. METHODS: We retrospectively reviewed medical records of 40 male and 31 female neonates diagnosed as congenital hypothyroidism by newborn screening from 1996 to 2003. The untreated cases that revealed slightly decreased levels of thyroid hormone on repeated examination and the cases who showed normalized hormone after 2 years of treatment were regarded as transient hypothyroidism. The results of neonatal screening tests and other clinical features of children with transient hypothyroidism were compared to those of children with permanent form. The time to normalization of thyroid hormone levels in the transient hypothyroidism were also reviewed. RESULTS: Among 71 cases of congenital hypothyroidism, 39 cases (54.9%) were transient and 32 cases (45.1%) were permanent hypothyroidism. There were no significant differences in clinical features between two groups, except lower birth weight in the transient group (transient 2.80+/-0.75 kg, permanent 3.22+/-0.57 kg, P=0.02). Free T4 levels were significantly lower and TSH levels were significantly higher in the permanent form than the transient ones (P<0.01). The estimated cut-off point for distinguishing transient hypothyroidism from permanent form was 2.05 ng/dL (sensitivity 54%, specificity 93%) for free T4 and 34 microIU/mL (sensitivity 72%, specificity 87%) for TSH. CONLCUSION In this study, transient hypothyroidism could be differentiated from permanent hypothyroidism by TSH and free T4 levels of neonatal screening test. Repeated thyroid function tests are thought to be essential to make a diagnosis of not only transient but also permanent hypothyroidism.