Predictors of transient congenital hypothyroidism in children with eutopic thyroid gland

PURPOSE Congenital hypothyroidism (CH) is the most common cause of preventable mental retardation. Recently, the detection of CH cases with eutopic thyroid gland has increased due to neonatal screening programs. In this study, we aimed to identify and evaluate predictive factors that could distinguish between permanent and transient CH in patients with eutopic thyroid gland. METHODS We retrospectively reviewed 100 children diagnosed with CH and with eutopic thyroid gland. All subjects were treated with levothyroxine and underwent re-evaluation after 3 years of age. RESULTS Of the 100 CH patients, 35 (35.0%) were diagnosed with permanent CH (PCH) and 65 (65.0%) were diagnosed with transient CH (TCH). The initial thyroid stimulating hormone levels were significantly lower in the TCH subjects than in PCH subjects. In addition, the mean doses of levothyroxine (µg/kg/day) at the 1st, 2nd, and 3rd year of treatment were significantly lower in subjects with TCH than in PCH subjects with eutopic thyroid gland. Based on the receiver operating characteristic (ROC) curve, the optimal cutoff dose of levothyroxine at 3 years of 2.76 µg/kg/day could predict TCH, and was associated with 87.3% sensitivity and 67.6% specificity, with an area under the ROC curve of 0.769. CONCLUSION The levothyroxine dose requirement during treatment period has a predictive role in differentiating TCH from PCH in CH patients with eutopic thyroid gland.