Thyroid function in < 32 weeks gestation preterm infants.

INTRODUCTION: Preterm newborns (PN) have a higher risk of thyroid dysfunction than term newborns (TN). This condition may go unnoticed in neonatal screening due to a late elevation of thyrotropin (TSH) in these patients. OBJECTIVE: Evaluate thyroid function in the second week of life in PN of < 32 weeks gestation (WG), and to identify factors associated to its alteration. PATIENTS AND METHODS: A retrospective study was performed in neonates of < 32 weeks gestation (WG), in whom thyroid function was determined. An analysis was performed on thyroxine (T4L) and TSH levels, as well as their association with perinatal and neonatal outcomes. RESULTS: The study included a total of 358 patients with mean gestational age (GA) of 29.3 weeks, and mean birth weight (BW) 1127 grams. A linear correlation was found between T4L and BW (correlation coefficient (R) 0.356; p < 0.001) and GA (R = 0.442; p < 0.001). TSH values were associated with small for gestational age (SGA 5.3 mU/L [1.5-37]; non-SGA 2.89 mU/L [0.2-19.5]; p < 0.001), inotropic support (Yes 3.98 mU/L [0.6-22.9]; No 3.16 mU/L [0.2-37]; p = 0.019) and BW (R = -0.249; p < 0.001). Nine (2.5%) patients were treated with levothyroxine, of whom six were SGA. CONCLUSIONS: Thyroid function analysis in the second week of life helps to identify asymptomatic newborns with risk of thyroid dysfunction. SGA newborns are at higher risk of thyroid function alterations.

Función tiroidea en el recién nacido prematuro con edad gestacional igual o menor a 32 semanas / Thyroid function in < 32 weeks gestation preterm infants

Introducción: El recién nacido (RN) prematuro (RNPT) tiene mayor riesgo de disfunción tiroidea que el recién nacido a término (RNAT). Esta alteración puede pasar desapercibida en el cribado neonatal por una elevación tardía de tirotropina (TSH) en estos pacientes. Objetivo: Evaluar la función tiroidea en la segunda semana de vida en RNPT menores a 32 semanas de gestación (SG) e identificar factores asociados con la alteración de esta. Pacientes y métodos: Estudio restrospectivo que incluye RNPT de igual o menos de 32 SG, a los que se realizó función tiroidea. Se analizaron los valores de tiroxina (T4L) y TSH y su relación con variables perinatales y de evolución neonatal. Resultados: Se presentaron 358 pacientes con edad gestacional (EG) mediana de 29,3 semanas y peso al nacimiento (PN) de 1.127 gramos. Se encontró correlación lineal entre T4L y el PN (coeficiente de correlación (R) 0,356; p < 0,001) y la EG (R = 0,442; p < 0,001). Los valores de TSH se asociaron con ser pequeño para la edad gestacional (PEG 5,3 mU/L [1,5 a 37]; no PEG 2,89 mU/L [0,2 a 19,5]; p < 0,001), al soporte inotrópico (Sí 3,98 mU/L [0,6 a 22,9]; No 3,16 mU/L [0,2 a 37]; p = 0,019) y al PN (R = -0,249; p < 0,001). Recibieron tratamiento sustitutivo con levotiroxina nueve pacientes (2,5%), seis de los cuales fueron PEG. Conclusiones: El análisis de la función tiroidea en la segunda semana de vida permite identificar RNPT asintomáticos con riesgo de presentar alteración de la función tiroidea. Los RN PEG tienen un riesgo más elevado de disfunción tiroidea. (AU)

Introduction: Preterm newborns (PN) have a higher risk of thyroid dysfunction than term newborns (TN). This condition may go unnoticed in neonatal screening due to a late elevation of thyrotropin (TSH) in these patients. Objective: Evaluate thyroid function in the second week of life in PN of < 32 weeks gestation (WG), and to identify factors associated to its alteration. Patients and methods: A retrospective study was performed in neonates of < 32 weeks gestation (WG), in whom thyroid function was determined. An analysis was performed on thyroxine (T4L) and TSH levels, as well as their association with perinatal and neonatal outcomes. Results: The study included a total of 358 patients with mean gestational age (GA) of 29.3 weeks, and mean birth weight (BW) 1127 grams. A linear correlation was found between T4L and BW (correlation coefficient (R) 0.356; p < 0.001) and GA (R = 0.442; p < 0.001). TSH values were associated with small for gestational age (SGA 5.3 mU/L [1.5-37]; non-SGA 2.89 mU/L [0.2-19.5]; p < 0.001), inotropic support (Yes 3.98 mU/L [0.6-22.9]; No 3.16 mU/L [0.2-37]; p = 0.019) and BW (R = -0.249; p < 0.001). Nine (2.5%) patients were treated with levothyroxine, of whom six were SGA. Conclusions: Thyroid function analysis in the second week of life helps to identify asymptomatic newborns with risk of thyroid dysfunction. SGA newborns are at higher risk of thyroid function alterations. (AU)

[Thyroid function in < 32 weeks gestation preterm infants]. / Función tiroidea en el recién nacido prematuro con edad gestacional igual o menor a 32 semanas.

INTRODUCTION: Preterm newborns (PN) have a higher risk of thyroid dysfunction than term newborns (TN). This condition may go unnoticed in neonatal screening due to a late elevation of thyrotropin (TSH) in these patients. OBJECTIVE: Evaluate thyroid function in the second week of life in PN of < 32 weeks gestation (WG), and to identify factors associated to its alteration. PATIENTS AND METHODS: A retrospective study was performed in neonates of < 32 weeks gestation (WG), in whom thyroid function was determined. An analysis was performed on thyroxine (T4L) and TSH levels, as well as their association with perinatal and neonatal outcomes. RESULTS: The study included a total of 358 patients with mean gestational age (GA) of 29.3 weeks, and mean birth weight (BW) 1127 grams. A linear correlation was found between T4L and BW (correlation coefficient (R) 0.356; p < 0.001) and GA (R = 0.442; p < 0.001). TSH values were associated with small for gestational age (SGA 5.3 mU/L [1.5-37]; non-SGA 2.89 mU/L [0.2-19.5]; p < 0.001), inotropic support (Yes 3.98 mU/L [0.6-22.9]; No 3.16 mU/L [0.2-37]; p = 0.019) and BW (R = -0.249; p < 0.001). Nine (2.5%) patients were treated with levothyroxine, of whom six were SGA. CONCLUSIONS: Thyroid function analysis in the second week of life helps to identify asymptomatic newborns with risk of thyroid dysfunction. SGA newborns are at higher risk of thyroid function alterations.

Effect of the multiple scattering of electrons in Monte Carlo simulation of LINACS.

Results obtained from Monte Carlo simulations of the transport of electrons in thin slabs of dense material media and air slabs with different widths are analyzed. Various general purpose Monte Carlo codes have been used: PENELOPE, GEANT3, GEANT4, EGSNRC, MCNPX. Non-negligible differences between the angular and radial distributions after the slabs have been found. The effects of these differences on the depth doses measured in water are also discussed.