Objectives: Early and proper treatment is crucial to prevent neuropsychologic deficits in congenital hypothyroidism (CH). Considering the high prevalence of CH in Isfahan, the aim of this study was to evaluate

the outcome of treatment in CH patients.
Methods: In this study CH neonates diagnosed during screening program in Isfahan from May 2002 to September 2009 were studied. Frequent visits were performed to CH patients to monitor and follow their treatments. Quality of treatment was assessed by evaluating mean age of treatment initiation and mean TSH and T4 levels before and after treatment and during the first and second years according to their normal reference ranges.
Results: Of 225,224 screened neonates, 536 were diagnosed as CH patients. The prevalence of CH was 1/420 live births. Mean age at starting treatment was 22.9 ± 13.2 days. In 93.7% of patients, treatment was begun before the 45th day of life. In the first measurement after initiating the treatment, T4 and TSH were not in their acceptable range in 3.9% and 9.8% of CH patients, respectively. Mean T4 and TSH reached to normal range during the treatment period. T4 reached the normal range earlier than TSH.
Conclusions: The mean age of treatment initiation was in acceptable range but the findings suggest that both early and high-dose treatments are crucial for optimal treatment, especially in patients with severe CH. Further studies are needed to determine the outcome of treatment specially regarding to different etiologies of CH.