RESUMEN
In Iran thyroid-stimulating hormone [TSH] based neonatal screening program is included in health care services from 2005 for detection of patients with primary congenital hypothyroidism [CH]. This study was performed for a critical evaluation of the screening program primary congenital hypothyroidism in Fars province, Iran. From November 2006 to September 2007, TSH serum concentrations of 63031 newborns, 3 to 5 days old born in Fars province, were measured by heel prick. The newborns with TSH >/= 5mIU/L were recalled for measurement of serumT4 and TSH in venous blood samples Of 127 recalled subjects, 43 were confirmed to be hypothyroid, showing a prevalence of 1:1465 with F:M ratio of 1.05:1. The most common clinical and radiological findings were prolonged jaundice [73%], large anterior fontanel [56%], wide posterior fontanel [55%], absence of distal femoral epiphysis [20%], and umbilical hernia [11%]. Scintigraphy of the thyroid with [99m]TC revealed eutopia [67.4%], hypoplasia [23.3%], agenesis [4.7%] and ectopia [2.3%]. It is concluded that a cut off value of TSH >/= 5mIU/L overestimates recalling the number of patients with CH. The most common cause of congenital hypothyroidism is not dysgenesis of the gland and perhaps dyshormonogenesis in Iran is more common than what is reported in other countries