Jornal de Pediatria (Jun 2001)
Efeitos da asfixia perinatal sobre os hormônios tireoidianos Effect of perinatal asphyxia on thyroid hormones
Abstract
OBJETIVO: verificar o efeito da asfixia perinatal sobre os hormônios tireóideos. MÉTODOS: Foi realizado um estudo de caso-controle, no hospital de Clínicas de Porto Alegre, envolvendo 17 recém-nascidos a termo asfixiados (A) e 17 não-asfixiados (N), pareados conforme a cor, sexo, tipo de parto, idade gestacional e peso de nascimento. Foram coletados T4, T3, T4 livre, T3 reverso e TSH do sangue do cordão e do recém-nascido com 18 a 24 horas de vida, entre os que sofreram ou não asfixia perinatal. RESULTADOS: No sangue de cordão, não houve diferença na dosagem dos hormônios tireóideos, com exceção do T3 reverso, que foi mais elevado no grupo que sofreu asfixia [mediana (percentis 25-75) :A= 2(1,4-2); N= 1,41(1,13-1,92); p=0,037]. Com 18 a 24 horas de vida, foram significativamente menores no grupo de asfixiados, com exceção do T3 reverso, que foi semelhante entre os dois grupos [média ± DP: T4 A= 9,79 ± 2,59; N=14,68 ± 3,05; p OBJECTIVE: to verify the effect of perinatal asphyxia on thyroid hormone levels in term newborn infants. METHODS: We carried out a case-control study with 17 term and asphyxiated (A) and 17 term and control (N) newborn infants at the Hospital de Clínicas de Porto Alegre. Patients were paired according to color of skin, sex, type of delivery, gestational age, and weight at birth. We collected umbilical cord plasma T4, T3, free T4, reverse T3, and TSH after 18 to 24 hours of life and from asphyxiated and control newborn infants. RESULTS: There were no differences in thyroid hormones of cord blood, with the exception of reverse T3, which was higher in A than in controls [median (25th-75th percentile): A= 2(1.4-2); N= 1.41 (1.13-1.92); P=0.037)]. Thyroid hormone levels were lower in A than in controls on samples collected within 18-24 hours after birth, except for reverse T3, which was similar in both groups [average ± SD: T4 A= 9.79 ± 2.59; N=14.68 ± 3.05; P<0.001; median T3 A= 40.83 (37.4-80.4); N= 164 (56.96-222.5); P=0.003; average ± SD: free T4 A=1.85 ± 0.92; N= 2.8 ± 0.74; P=0.004; median: reverse T3 A=1.54 (1.16-1.91); N=1.31(0.87-2); P=0.507; TSH A=9.1 (6.34-12.95); N=14.5(12.9-17.85); P=0.008]. CONCLUSIONS: Our data suggest that lower T4, free T4, and T3 levels are secondary to lower TSH levels in asphyxiated newborns; also, peripheral metabolism of T4 in asphyxiated infants can be altered due to low T3 and normal reverse T3 levels.
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