Background and Aim: Congenital hypothyroidism (CH) is among the most common endocrine disorders in children and a preventable cause of mental retardation. The present study was performed to determine the prevalence and related risk factors of hypothyroidism in neonates in South Khorasan.

  Materials and Methods: This descriptive-retrospective study was conducted on the data collected through the Neonatal CH Screening Project in South Khorasan during four years (March 2006 - March 2010). Neonates whose TSH of the heel blood was ≥5 mU/L were recalled and if the serum TSH was ≥10 mU/L they were accounted as hypothyroid cases. Finally, SPSS software was used to analyze the obtained data.

  Results: From 38987 neonates, 1248 cases (3.21%) were recalled and serum TSH of 71 neonates was ≥10 mU/L which was a symptom of hypothyroidism. In the initial screening of hypothyroidism in neonates TSH of the heel blood in 45% was found to be 5-10 mU/L, in 20% it was 10-19.9, and in 35% it was ≥ 20. Prevalence of the disease was 1 in 549 living births. Hypothyroidism in boys was 6% more than girls.98.6% of the sick neonates' mothers did not have hypothyroidism 50.7 % of the cases lived in city.

  Conclusion: Regarding the significance of the disease in developing mental retardation, it is necessary to persuade parents to have their neonates take part in neonatal hypothyroidism screening plan.