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ABSTRACT Objective: Thyroid functions in preterm newborns may be altered in the first week of life. Hypothyroxinemia has been commonly reported in these babies, which could be due to the immaturity of the hypothalamic pituitary thyroid axis or acute illness. It could have a long-term impact on the developing brain of these babies. We conducted this study to estimate the incidence of transient hypothyroxinemia of prematurity (THOP) and to determine its risk factors. Materials and methods: We analyzed thyroid stimulating hormone (TSH) and free T4 levels of 64 preterm neonates admitted in the neonatal intensive care unit. TSH and free T4 levels were measured in the first week and then at 14-21 days of life to estimate the incidence of THOP and determine its risk factors. We also estimated the incidence of congenital hypothyroidism (CH) and delayed TSH elevation in CH. Risk analysis was conducted using simple and multiple logistic regression, and numerical data was compared using the Mann Whitney U test and t test. Results: THOP was seen in 25% of the preterm babies. Caesarean delivery, presence of one or more morbidities, mechanical ventilation, birth weight ≥ 1,500 g, and gestational age ≥ 32 weeks were identified as risk factors for THOP based on simple logistic regression. In multiple regression, mechanical ventilation and gestational age ≥ 32 weeks were significantly associated with THOP. CH was seen in 2 (3.1%) babies, and 1 of these cases had delayed TSH elevation. Conclusion: Thyroid abnormalities are common in preterm admitted neonates. Mechanical ventilation is an independent risk factor for development of THOP.

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OBJECTIVE: Thyroid functions in preterm newborns may be altered in the first week of life. Hypothyroxinemia has been commonly reported in these babies, which could be due to the immaturity of the hypothalamic pituitary thyroid axis or acute illness. It could have a long-term impact on the developing brain of these babies. We conducted this study to estimate the incidence of transient hypothyroxinemia of prematurity (THOP) and to determine its risk factors. METHODS: We analyzed thyroid stimulating hormone (TSH) and free T4 levels of 64 preterm neonates admitted in the neonatal intensive care unit. TSH and free T4 levels were measured in the first week and then at 14-21 days of life to estimate the incidence of THOP and determine its risk factors. We also estimated the incidence of congenital hypothyroidism (CH) and delayed TSH elevation in CH. Risk analysis was conducted using simple and multiple logistic regression, and numerical data was compared using the Mann Whitney U test and t test. RESULTS: THOP was seen in 25% of the preterm babies. Caesarean delivery, presence of one or more morbidities, mechanical ventilation, birth weight ≥ 1,500 g, and gestational age ≥ 32 weeks were identified as risk factors for THOP based on simple logistic regression. In multiple regression, mechanical ventilation and gestational age ≥ 32 weeks were significantly associated with THOP. CH was seen in 2 (3.1%) babies, and 1 of these cases had delayed TSH elevation. CONCLUSION: Thyroid abnormalities are common in preterm admitted neonates. Mechanical ventilation is an independent risk factor for development of THOP.

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OBJECTIVES: To determine the incidence of congenital hypothyroidism in preterm infants and to identify associated risk factors. STUDY DESIGN: A population-based cohort study was performed in preterm infants born at <32 weeks of gestational age between 2012 and 2016 in Wisconsin. Newborn screening (NBS) results and demographic data were obtained from the Wisconsin State Laboratory of Hygiene. Congenital hypothyroidism was subdivided to early TSH elevation (eTSH) and delayed TSH elevation (dTSH). Multivariate logistic regression analyses were performed to identify demographic factors associated with dTSH. RESULTS: A total of 3137 preterm infants born at 22-31 weeks of gestational age were included in the study. Mean gestational age was 28.4 ± 2.4 weeks and mean birth weight was 1191 ± 399 g. Forty-nine infants were diagnosed with congenital hypothyroidism. The overall incidence of congenital hypothyroidism was 1.56%, including a 0.13% incidence of eTSH and a 1.43% incidence of dTSH. Birth weight <1000 g, multiple gestation, and initial TSH level were identified as independent predictors for dTSH. CONCLUSION: Targeted serial NBS in Wisconsin led to a higher rate of diagnosis of congenital hypothyroidism in preterm infants than has been reported previously. The majority (92%) of congenital hypothyroidism cases were diagnosed with dTSH. Birth weight <1000 g, multiple gestation, and elevated initial TSH level were associated with increased risk for development of dTSH. We recommend obtaining targeted serial NBS in preterm infants (<32 weeks of gestational age) to improve the detection of congenital hypothyroidism.

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INTRODUCTION: Patients with Down syndrome (DS) often have elevated TSH (hypothalamic origin), which is called TSH neurosecretory dysfunction (TSH-nd). In these cases, there is slight elevation in TSH (5-15 µUI/mL), with normal free T4 and negative thyroid antibodies (AB). OBJECTIVE: To recognize the risk of progression to Hashimoto's thyroiditis (HT). SUBJECTS AND METHODS: We retrospectively analyzed 40 DS patients (mean age = 4.5 years), followed up for 6.8 years. RESULTS: HT was diagnosed in 9/40 patients, three early in monitoring, and six during evolution. In 31/40 patients, TSH-nd diagnosis remained unchanged over the years, with maximum TSH values ranging from 5 to 15 µUI/mL. In this group, free T4 also remained normal and AB were negative. There was a significant TSH reduction (p = 0.017), and normal TSH concentrations (< 5.0 µUI/mL) were observed in 29/31 patients, in at least one moment. No patient had TSH > 15 µUI/mL. CONCLUSION: DS patients with TSH-nd present low risk of progression to HT (10 percent for females and 6 percent for males).

INTRODUÇÃO: Pacientes com síndrome de Down (SD) geralmente apresentam TSH elevado (de origem hipotalâmica), uma desordem chamada de disfunção neurossecretora de TSH (TSH-nd). Nesses casos, há uma leve elevação do TSH (5-15 µUI/mL), com T4 livre normal e anticorpos antitireoide (AB) negativos. OBJETIVO: Reconhecer o risco de progressão para a tireoidite de Hashimoto (HT). SUJEITOS E MÉTODOS: Analisamos retrospectivamente 40 pacientes com SD (idade média = 4,5 anos), acompanhados por 6,8 anos. RESULTADOS: A HT foi diagnosticada em 9/40 pacientes, três logo no início da avaliação e seis durante a evolução. Em 31/40 dos pacientes, o diagnóstico de TSH-nd permaneceu estável durante os anos, com valores máximos de TSH variando de 5 a 15 µUI/mL. Neste grupo, o T4 livre também permaneceu normal e os AB foram negativos. Houve uma redução significativa do TSH (p = 0,017), e concentrações normais de TSH (< 5,0 µUI/mL) foram observadas em 29/31 pacientes, em pelo menos um momento. Nenhum paciente apresentou TSH > 15 µUI/mL. CONCLUSÃO: Pacientes com SD e TSH-nd apresentam baixo risco de progressão para a HT (10 por cento para o sexo feminino e 6 por cento para o sexo masculino).

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