Permanent and transient neonatal hypothyroidism in Tehran

The incidence of permanent and transient CH has not yet been determined in Iran. This report illustrates the incidence of permanent and transient CH in Tehran and Damavand. From February 1998 to August 2002, cord dried blood spot samples in Tehran and Damavand were collected and those with TSH 20 mU/L were recalled (two-site IRMA). Between 7-14 days of life or thereafter, CH was confirmed by serum TSH >10 mU/L and T4 <6.5 g/dL or TSH >30 mU/L alone and L-T4 was immediately started. CH-affected newborns were followed-up until May 2003. Dysgenesis was determined using 99mTC thyroid scanning and /or ultrasonography. In thyroid eutopic newborns, dyshormonogenesis was diagnosed by a 4-week discontinuation of L-T4 between 2-3 years of age and abnormal serum TSH and T4 values, while normal levels after discontinuation confirmed transient CH. Cases with incomplete early follow-ups without thyroid imaging, were known as unknown CH. Of 35067 screened neonates 373 had cord TSH 20 mU/L and were recalled (recall rate: 1.06%). 35 had CH (incidence of 1:1002 births), 25 had permanent CH (incidence of 1:1403 births), and 6 had transient CH (incidence of 1:5845 births). The type of CH remained unknown in 4 cases. Thyroid dysgenesis and dyshormonogenesis were detected in 18 (incidence of 1:1948 births) and 7 cases (incidence of 1:5010 births), respectively. The high incidence of permanent CH underlines the necessity to implement a national CH screening program in Iran.