Thyroid hormone resistance detected by routine neonatal screening / Resistência ao hormônio tireoidiano detectada por meio da triagem neonatal

ABSTRACT

We report the clinical and laboratory findings, and molecular analysis of a Brazilian patient with resistance to thyroid hormone syndrome (RTH) detected by neonatal screening. The index case was born at term by normal delivery with 2,920 g and 45 cm. TSH of the neonatal screening test performed on the 5th day of life was of 13.1 µU/mL (cut-off = 10 µU/mL). In a confirmatory test, serum TSH level was 4.3 µU/mL, total T4 was 19 µg/dL (confirmed in another sample, Total T4 = > 24.0 µg/dL), free T4 was 3.7 ηg/dL, and free T3 was 6.7 pg/mL. Direct sequencing of the beta thyroid hormone receptor gene revealed mutation c.1357C>A (P453T), confirming the diagnosis of RHT. Family study demonstrated the presence of RTH in his 1-year-and-3-month-old sister, in his 35-year-old father, and in his 68-year-old paternal grandfather. All of them had goiter and only his father had received an erroneous diagnosis of hyperthyroidism. The present case shows that clinical evaluation and a judicious interpretation of total T4/free T4 concentrations in a newborn recalled due to slightly altered neonatal TSH can contribute to the diagnosis of RTH.

RESUMO

O objetivo deste estudo é relatar o caso de um paciente brasileiro com resistência ao hormônio tireoidiano (RTH) detectado por meio da triagem neonatal. O caso índice nasceu de parto normal a termo com peso de 2.920 g e estatura de 45 cm. Realizou o teste de triagem neonatal no quinto dia de vida com TSH neonatal = 13,1 µU/mL (valor de corte = 10 µU/mL). O TSH confirmatσrio no soro foi de 4,3 µU/mL, T4 Total de 19 µg/dL (confirmado em outra amostra, T4 Total = > 24,0 µg/dL), T4 Livre de 3,7 ηg/dL e T3 Livre de 6,7 pg/mL. O sequenciamento direto do gene do receptor βdo hormínio tireoidiano revelou a mutação c.1357C>A (P453T), confirmando o diagnóstico de RHT. O estudo de sua família confirmou RTH em sua irmã (1 ano e 3 meses), em seu pai (35 anos) e em seu avô paterno (68 anos). Todos apresentavam bócio e apenas seu pai havia recebido o diagnóstico errôneo de hipertireoidismo. Este caso ilustra que a avaliação clínica e a interpretação criteriosa das concentrações de T4 Total/Livre em um recém-nascido, reconvocado por TSH neonatal discretamente alterado, poderão servir para o diagnóstico da RTH.