High prevalence of congenital hypothyroidism in Isfahan, Iran

Hypothyroidism is one of the preventable causes of mental retardation, which according to its clinical manifestations within the neonatal period, can be diagnosed in only fewer than 10% of cases. Delayed diagnosis results in irreversible cerebro-auditory complications unless the problem is diagnosed by screening programs.

From May to December 2002, T4 and TSH concentrations of 20,000 serum samples obtained from newborns on 3rd-7th day of birth, born in seventeen hospitals throughout Isfahan were measured by RIA and IRMA, respectively. The newborns with abnormal screening results (TSH> 20 mIU/L, T4<6.5 μg/dL and based on the weight) were re-examined. Newborns with TSH >10mIU/L and T4<6.5 μg/dL on the second measurement were considered to be hypothyroid so treatment was begun. After performing complementary tests, the hypothyroid patients received replacement therapy with levothyroxine.

From 20,000 neonates that were examined, 531 were recalled (Recall rate = 2.65%) and 54 newborns were diagnosed as hypothyroid. The prevalence of neonatal hypothyroidism was estimated to be 1/370.

Considering the high prevalence of the disease in the population, the necessity of routine neonatal screening programs is underscored.