Intellectual outcomes of patients with congenital hypothyroidism not detected by neonatal screening

Mental retardation is a major sequela of delayed treatment of congenital hy pothyroidism. In this study, we investigated the intellectual outcomes of p atients with congenital hypothyroidism diagnosed before a nationwide screen ing project started, Eight-two patients had intelligence tests done while i n the euthyroid state, Their mean intelligence quotient (IQ) was 78 +/- 21 (+/- SD) (n = 79). The mean verbal IQ was significantly higher than the mea n full-scale IQ. The mean IQs of both ectopic thyroid (84 +/- 21, n = 28) a nd dyshormonogenic patients (85 +/- 14, n = 18) were significantly higher t han that of patients with athyrosis (64 +/- 18, n = 19) (p < 0.05). Patient s who were treated before 3 months of age had significantly higher mean IQs (90 +/- 16, n = 16) than those treated after 3 months (75 +/- 21, n = 63) (p < 0.01). Our results confirm that both patients with ectopic thyroids an d those with dyshormonogenesis have better intellectual outcomes than athyr otic patients do, and that early treatment improves the intellectual outcom e of patients with congenital hypothyroidism.