Avaliação do eixo hipotalâmico-hipofisário-tireoidiano em crianças com síndrome de Down / Evaluation of the hypothalamic-pituitary-thyroid axis in children with Down syndrome

Objetivo: determinar a secreção de TSH em crianças comsíndrome de Down, sem quadro clínico-laboratorial clássico de hipotireoidismo. Métodos: analisou-se 14 crianças com síndrome de Down e idade média de 3,4 (Ý1,8) anos. Excluiu-se pacientes com sintomas clássicos de hipotireoidismo ou hipertireoidismo, ou que apresentas-sem anticorpos antitireóide positivos. Os pacientes foram comparados a um grupo controle de 16 pacientes com idade média de 11,8 (Ý3,8) anos e diagnóstico de baixa estatura familial ou atraso constitucional do crescimento. Foram determinadas as concentraçies de TSH, T3, T4, T4L e prolactina no tempo basal e após estímulo com TRH. Pacientes com síndrome de Down, subdivididos quanto ao TSH basal, foram comparados em relação às concentraçies basais de T3, T4, T4L e prolactina.Resultados: os valores basais de TSH e de prolactina foram significativamente majores no grupo com síndrome de Down. Após estímulo com TRH, o pico de TSH foi major no grupo com síndrome de Down. Tanto o número de pacientes com TSH basal > 5 µ.U/ml, quanto o número dos que apresentaram hiper-resposta ao estímulocom TRH (pico de TSH > 30 µ.U/ml), foi major no grupo comsíndrome de Down.Conclusões: freqüentemente, crianças portadoras de síndrome de Down apresentam elevação do TSH basal, mesmo na presença de valores basais normais de hormônios tireoidianos e anticorpos antitireóide negativos. A maioria dessas crianças (65por cento) apresenta hiper-resposta...

[Evaluation of the hypothalamic-pituitary-thyroid axis in children with Down syndrome]. / Avaliação do eixo hipotalâmico-hipofisário-tireoidiano em crianças com síndrome de Down.

OBJECTIVE: To determine the thyroid stimulating hormone (TSH) secretion in children with Down syndrome (DS), who do not present clinical and laboratory evidence of classical hypothyroidism and concomitant undetectable antibodies. METHODS: Fourteen children with DS with a mean age of 3.4 (+/- 1.8) years were studied. Patients with classical hypothyroidism or hyperthyroidism or those with positive antithyroid antibodies were excluded. The DS group was compared to a control group of 16 children with a mean age of 11.8 (+/- 3.8) years, diagnosed as having familial short stature or constitutional growth delay. Both groups underwent hormonal measurements at basal condition to determine serum TSH, T3, T4, free T4 and prolactin concentrations and after stimulation with thyrotropin releasing hormone (TRH). Thyroid hormones concentrations were also compared when children with DS were subdivided into two groups according to their basal TSH levels. RESULTS: Basal TSH and prolactin levels were significantly higher in DS group. After stimulation with TRH, TSH peak was higher in the DS group. The number of patients presenting basal TSH levels higher than 5 microU/mL and TSH peaks higher than 30 microU/mL were significantly higher in the DS group. CONCLUSIONS: Children with Down syndrome present frequent increase in basal TSH concentrations, despite the presence of normal basal thyroid hormones levels and negative antithyroid antibodies. Most of them (65%) show early intense response after TRH stimulation. Our data demonstrate that in spite of the absence of classic hypothyroidism and/or antithyroid antibodies, an abnormal pattern of TSH secretion occurred in patients with Down syndrome, possibly related to hypothalamic dysfunction.