Screening for congenital hypothyroidism in Tehran and Damavand: an interim report on descriptive and etiologic findings, 1998-2001

Screening for congenital hypothyroidism (CH) was re-established in Iran in 1998 following elimination of iodine deficiency. The incidence of CH and its etiologic factors in addition to some demographic features of the screened neonates were assessed. From 21 February 1998 to 21 June 2001 cord blood spot samples from 8 hospitals and a rural birth center were collected and tested for TSH measurement using a two-site IRMA method. TSH values  20 mU/mL were recalled. The diagnosis of CH was confirmed using age adjusted reference values for serum TSH and T4 levels and replacement L-T4 therapy, 10-15 g/kg/d, started promptly. Out of 20107 screened neonates 256 had cord TSH values 20 U/mL (recall rate: 1.3%) and 22 showed hypothyroidism (1: 914 live births). Median iodine excretion levels of 50 recalled neonates and 47 mothers were 37.5 and 21 g/dl, respectively. History of drugs and dietary goitrogens was negative. 15 out of 21 CH neonates had parental consanguinity. The odds ratio of CH occurrence in blood-related to non-related marriages was 6.9 (95% CI = 1.82-25.87) and the risk of CH in consanguineous marriages was 0.0036. Thyroid dysgenesis occurred in 10 neonates 1: 2011 births. There is a high incidence of CH and thyroid dysgenesis in Islamic Republic of Iran. Consanguineous marriages could be considered a probable causative factor for the increased incidence of CH in the study.