Intellectual outcome of patients with congenital hypothyroidism detected by neonatal screening

Background and purpose: Mental retardation is a major sequela of delayed tr eatment for congenital hypothyroidism; congenital hypothyroidism can be tre ated early if detected with neonatal screening. We evaluated the intellectu al outcomes of 62 patients with congenital hypothyroidism detected by neona tal screening at a major reaching hospital in northern Taiwan. The effects of thyroid pathology, age at the initiation of treatment, socioeconomic sta tus, and severity of hypothyroidism on intellectual outcome were also analy zed. Methods: All patients had euthyroid status at the time of intelligence test ing. The Chinese Fourth Revision of the Binet-Simon Scales was used to eval uate the patients' intelligence between the ages of 3 and 6 years. Results: The mean intelligence quotient (IQ) score was 102 +/- 18. Only fou r of the 62 patients were mentally retarded. Patients with lower initial se rum thyroxine concentrations (T4: < 2 mug/dL) at the time of diagnosis of c ongenital h! pothyroidism had significantly lower IQs (95 +/- 19, n = 26) t han those with higher initial T4 concentrations (106 +/- 16, n = 36; p < 0. 05). Patients with fewer than three ossification centers had lower IQs (91 +/- 20, n = 12) than those with three or more (104 +/- 17, n = 36; p < 0.05 ). Significantly lower IQs were also found in patients with a smaller femor al epiphysis area (<less than> 0.1 cm(2)) (92 +/- 20, n = 15) than in those with larger epiphyses (106 +/- 15, n = 21; P < 0.05). The type of patholog y (ectopia, athyrosis, dyshormonogenesis), age at the start of treatment (b efore or after 30 days of age), and socioeconomic status did not significan tly affect the intellectual outcome. Conclusions: Our results indicate that intellectual outcome in Taiwanese pa tients with congenital hypothyroidism has been improved by neonatal screeni ng and that the severity of hypothyroidism at diagnosis is the most importa nt prognostic factor affecting intellectual outcome in these patients.