Determining the Prognostic Factors of Permanent Congenital Hypothyroidism

Neonatal hypothyroidism, a preventable cause of mental retardation, has a high prevalence in Iran. Considering the high prevalence of the transient form of this disease, which recovers within 4-6 months after birth, it is important to determine factors that can differentiate between permanent and transient hypothyroidism in Iran.

In this retrospective cohort study, neonates born in 15 selected provinces of Iran in 2011 were included. The evaluated information in this study included cumulative data, routinely collected in the national screening program for congenital hypothyroidism.

A total of 598 (57.1%) infants were diagnosed with permanent congenital hypothyroidism, and 449 (42.9%) infants were diagnosed with transient congenital hypothyroidism. Based on the ROC curve analysis, serum thyroid-stimulating hormone (TSH) levels ​​above 20 mU/L predicted permanent cases with 75.2% sensitivity and 82% specificity. Also, serum thyroxine (T4) levels below 8.2 μg/dL predicted permanent cases with sensitivity of 72.1% and specificity of 64%. Overall, a serum TSH level ≥20 mU/L, a serum T4 level ≤8.2 μg/dL, parental consanguinity, and family history of thyroid diseases increased the risk of permanent hypothyroidism, respectively.

The serum levels of T4 and TSH are the most important prognostic factors for the prediction of permanent congenital hypothyroidism. Although it is not possible to make a definitive early diagnosis, we may be able to differentiate the transient form more quickly, with greater sensitivity and specificity, by conducting larger studies and advanced modeling; this would help medical teams discontinue long-term treatments for transient cases and reduce the financial and emotional burdens on families.