Prognostic factors in the intellectual development at 7 years of age in children with congenital hypothyroidism

Abstract

The influence of the initial L-T4 dose and some other factors on the intellectual development was evaluated at 7 years of age in 47 congenitally hypothyroid children detected by the regional screening program. All patients were initially treated with 25 micrograms LT4/kg/day that represented a mean replacement dose of 6.8 +/- 1.3 micrograms/kg. Despite the "low" initial dose mean IQ at 7 years resulted within normal range (96 +/- 9). Twenty-eight patients initially treated with 6.0 +/- 0.6 micrograms L-T4/kg/day had a mean IQ (96 +/- 9) which was not different with respect to 19 patients (IQ 94 +/- 7) treated with a significantly higher L-T4 dose (8.1 +/- 0.9 micrograms/kg/day; p < 0.0001). The initial L-T4, dose did not correlate with IQ at 7 years whereas a significant correlation was found between IQ and serum T4 concentration at diagnosis (r = 0.35; p < 0.01) regardless of the fact that serum T4 concentration normalized after the first 2 months of therapy in both groups. Twenty-three patients whose serum T4 at diagnosis was < 2 micrograms/dl (1.0 +/- 0.5) had a mean IQ at 7 years (92 +/- 9) which was significantly lower than the 24 patients (IQ 98 +/- 7; p < 0.02) whose serum T4 was > 2 micrograms/dl (5.7 +/- 2.4; p < 0.001). The present findings suggest that the severity of neonatal hypothyroidism is an important factor in determining subsequent intellectual development of congenitally hypothyroid children.

School attainments in children with congenital hypothyroidism detected by neonatal screening and treated early in life

“…Although in our (18,40) and others' (14,15,17,41,42) experience, a low neonatal T 4 level is a risk factor for a defective neuropsychological development, in the present study the degree of neonatal thyroid hormone deficiency was not found to be a major variable influencing school learning. In this regard, our results do not completely agree with the recent observation that a low neonatal T 4 is associated with less satisfactory scores for educational attainments (21).…”

Intellectual outcome at 12 years of age in congenital hypothyroidism

“…All patients had normal thyroid function studies when the test was administered (serum T 4 > 103 nmol/l; serum TSH <5 mU/ml). The IQ scores were compared with the results of developmental and intellectual evaluation performed at 2 years (Brunet-Lezine test) and at 7 years of age (Stanford-Binet) respectively (9).…”

“…Although neurological development is generally good in treated children (1)(2)(3), subtle motor and cognitive deficits and impaired intellectual outcome have been detected in some cases (4)(5)(6)(7)(8)(9)(10). These slight neurological deficits are related to the severity of congenital hypothyroidism at diagnosis as assessed by serum thyroxine (T 4 ) concentrations or bone age (4,(6)(7)(8)(9)11), to the age at diagnosis (12), and to the dose of L-thyroxine replacement therapy (13)(14)(15)(16). The results of two studies that monitored patients during adolescence are conflicting: the New England Congenital Hypothyroidism Collaborative study (3) did not find differences in cognitive or in school performance among patients, their siblings or classmates in 14 years of follow-up, whereas Glorieux et al (6) detected lower intelligence quotient (IQ) scores in 12-year-old children whose hypothyroidism was more severe at diagnosis.…”

Situação atual da triagem neonatal para hipotireoidismo congênito: críticas e perspectivas

“…Estudos clínicos têm demonstrado que algumas variáveis influenciam o quociente de inteligência (QI) das crianças com HC: gravidade da doença (baixa concentração de T4 inicial e atraso na maturação esquelética no RN); idade no início do tratamento; dose de levotiroxina e concentrações séricas de T4 durante o primeiro ano de vida (17,(36)(37)(38)(39)(40)(41).…”