[Reference levels of thyroid hormones in pregnant woman from Guadalajara]. / Valores de referencia de hormonas tiroideas en la población de gestantes de Guadalajara.

INTRODUCTION: Thyroid dysfunction during gestation impacts on maternal-fetal health and may influence the neurocognitive development of the child. Thyroid physiology changes during pregnancy and requires the establishment of specific reference levels per trimester and for each population and method. The objectives of our study were to analyse thyroid function throughout pregnancy and to establish reference levels for TSH and T4L in each trimester for our population and methodology. MATERIAL AND METHODS: Prospective analytical study of 598 pregnant women from March 2018 to October 2020. TSH, T4L, T3L, ATPO and ATG were determined in all of them. A total of 151 pregnant women were excluded due to positive thyroid immunity, previous thyroid disease in treatment with levothyroxine, twin pregnancy, diagnosis of hypothyroidism and hyperthyroidism in the request or absence of some of the parameters studied, with a reference population of 447 pregnant women. RESULTS: The reference levels for TSH were 0.07-3.14mIU/L for the first, 0.66-3.21mIU/L for the second and 0.52-2.97mIU/L for the third trimester. Reference levels for T4L were 0.81-1.19ng/dL for the first, 0.71-1.07ng/dL for the second and 0.69-1.06ng/dL for the third trimester. CONCLUSIONS: The reference levels for TSH and T4L obtained in this study differ from those used for the general population, which may have led to misclassification errors and unnecessary treatment in pregnant women.

Iodine status in pregnant women in northern Spain. Effect of iodised salt and iodine supplements on thyroid function.

INTRODUCTION: Iodine deficiency is linked to thyroid dysfunction, particularly in pregnant women. The objective of this study was to ascertain the iodine levels of women in the second trimester of pregnancy, analysing the influence of iodine ingestion on urinary iodine concentration (UIC) and maternal thyroid function. METHODS: A prospective observational study of pregnant women from Health Area IV of Asturias (northern Spain) recruited before 13 weeks of gestation between May and June 2017. A questionnaire on iodine intake was completed at the first visit, and urine and serum samples were collected at baseline and again during the second trimester. UIC, thyroid stimulating hormone (TSH) and free thyroxine (FT4) obtained in the second trimester of gestation were analysed and related to iodine intake. Thyroid autoimmunity was also analysed in half of the pregnant women at baseline. RESULTS: A total of 241 pregnant women were studied. Of these, 56.7% used iodised salt, 46.7% consumed ≥2 servings of dairy products daily and 88.1% took iodine supplements. Median UIC was 191µg/l (135.3-294µg/l), with 68.1% of the women having UIC ≥150µg/l. Only iodised salt consumption provided protection against iodine deficiency (odds ratio 0.35 [0.20-0.63], p=0.001). In women with no autoimmune thyroid disease (n=88), mean levels of TSH were lower in those that consumed iodised salt than in those that did not (respectively, 2.08±0.89mIU/l vs. 2.56±1.02mIU/l, p=0.025). In women with autoimmune thyroid disease (n=30), mean levels of TSH were higher in those that took iodine supplements than in those that did not (respectively, 2.97±1.25mIU/l vs. 1.16±0.41mIU/l, p=0.002). CONCLUSIONS: The pregnant women studied from Health Area IV in Asturias maintain adequate nutritional iodine status in the second trimester of gestation. In our sample, only the consumption of iodised salt was associated with adequate iodine nutrition, without affecting maternal thyroid function. Most of the women used iodine supplements, which was linked to higher levels of TSH in pregnant women with autoimmune thyroid disease.

TSH neonatal como marcador del estado de nutrición de yodo. Influencia de la yoduria y la función tiroidea maternas sobre la TSH neonatal / Neonatal TSH as a marker of iodine nutrition status. Effect of maternal ioduria and thyroid function on neonatal TSH

Introducción: La TSH neonatal (TSHn) es un marcador de nutrición de yodo en la población. La OMS relaciona una prevalencia<3% de TSHn>5mUI/L, obtenida a partir de las 72h del nacimiento, con un adecuado estado nutricional de yodo. El objetivo de este estudio es conocer la prevalencia de TSHn>5mUI/L en una población yodosuficiente y su relación con factores maternos, neonatales y obstétricos. Materiales y métodos: Se reclutaron 243 gestantes entre mayo-junio de 2017 en nuestra área sanitaria. Se realizó un cuestionario sobre consumo de yodo y determinación de yoduria, función y autoinmunidad tiroideas en el primer trimestre de gestación. Se analizó la TSHn entre 48-72h del nacimiento, así como otros factores obstétricos y neonatales. Resultados: La TSHn media fue 2,43±1,68mUI/L, con un 7,8% de neonatos con TSHn>5mUI/L. La TSHn más elevada pertenecía a los neonatos de madres con yodurias insuficientes (p=0,021) o con TSH>2,5mUI/L, tanto en autoinmunidad tiroidea negativa (p=0,049) como positiva (p=0,006). La yoduria materna<150μg/L fue un factor de riesgo de TSHn>5mUI/L (3,70 [1,06-14,60], p=0,046), mientras que el peso neonatal ≥2500g fue un factor protector (0,14 [0,02-1,00], p=0,038). Conclusiones: La prevalencia de TSHn>5mUI/L en nuestra área sanitaria fue elevada, según las recomendaciones de la OMS. Se asoció el déficit de yodo materno con mayor riesgo de TSHn>5mUI/L. Dado que en la actualidad la determinación de la TSHn se realiza antes de las 72h del nacimiento, precisamos de nuevos puntos de corte para continuar empleando la TSHn como marcador de nutrición de yodo. (AU)

Introduction: Neonatal thyroid stimulating hormone (nTSH) is a marker of iodine nutrition status in the population. The WHO considers a prevalence of less than 3% of nTSH levels greater than 5mIU/L in samples obtained within 72h from birth indicative of iodine sufficiency. The aim of this study was to determine the prevalence of nTSH levels greater than 5mIU/L in an iodine-sufficient population and its association with maternal, neonatal and obstetric factors. Materials and methods: A total of 243 pregnant women were recruited between May and June 2017 in our health area. A questionnaire of iodine intake was administered, in addition to determination of ioduria, thyroid function and autoimmunity in the first trimester of gestation. We analysed nTSH levels in samples collected between 48 and 72h post birth and other obstetric and neonatal factors. Results: The mean nTSH level (standard deviation) was 2.43 (1.68mIU/L), with 7.8% of neonates having levels greater than 5mIU/L. The highest nTSH levels corresponded to neonates of mothers with insufficient ioduria (p=.021) or TSH levels greater than 2.5mIU/L, in both the case of negative (p=0.049) and positive (p=0.006) thyroid autoimmunity results. Maternal ioduria greater than 150μg/L was a risk factor for nTSH levels greater than 5mIU/L (3.70 [1.06–14.60]; p=0.046), while a neonatal weight of 2500g or greater was a protective factor (0.14 [0.02–1.00]; p=0.038). Conclusions: The prevalence of nTSH levels greater than 5mIU/L in our health area was high based on the WHO recommendations. Maternal iodine deficiency was associated with a higher risk of nTSH levels less than 5mIU/L. Given that nTSH is currently measured before 72h post birth, we need new cut-off points to keep on using nTSH as a marker of iodine nutritional status. (AU)

Neonatal TSH as a marker of iodine nutrition status. Effect of maternal ioduria and thyroid function on neonatal TSH.

INTRODUCTION: Neonatal thyroid stimulating hormone (nTSH) is a marker of iodine nutrition status in the population. The WHO considers a prevalence of less than 3% of nTSH levels greater than 5 mIU/L in samples obtained within 72h from birth indicative of iodine sufficiency. The aim of this study was to determine the prevalence of nTSH levels greater than 5 mIU/L in an iodine-sufficient population and its association with maternal, neonatal and obstetric factors. MATERIALS AND METHODS: A total of 243 pregnant women were recruited between May and June 2017 in our health area. A questionnaire of iodine intake was administered, in addition to determination of ioduria, thyroid function and autoimmunity in the first trimester of gestation. We analysed nTSH levels in samples collected between 48 and 72h post birth and other obstetric and neonatal factors. RESULTS: The mean nTSH level (standard deviation) was 2.43 (1.68 mIU/L), with 7.8% of neonates having levels greater than 5 mIU/L. The highest nTSH levels corresponded to neonates of mothers with insufficient ioduria (P = 0.021) or TSH levels greater than 2.5 mIU/L, in both the case of negative (P = 0.049) and positive (P = 0.006) thyroid autoimmunity results. Maternal ioduria less than 150 µg/L was a risk factor for nTSH levels greater than 5 mIU/L (3.70 [1.06-14.60]; P = 0.046), while a neonatal weight of 2500 g or greater was a protective factor (0.14 [0.02-1.00]; P = 0.038). CONCLUSIONS: The prevalence of nTSH levels greater than 5 mIU/L in our health area was high based on the WHO recommendations. Maternal iodine deficiency was associated with a higher risk of nTSH levels greater than 5 mIU/L. Given that nTSH is currently measured before 72h post birth, we need new cut-off points to keep on using nTSH as a marker of iodine nutritional status.

Factores clínicos y ambientales asociados a la tiroiditis de Hashimoto / Clinical and environmental factors associated with Hashimoto's thyroiditis

Introducción: La tiroiditis de Hashimoto es una enfermedad tiroidea autoinmune poligénica y multifactorial resultante de una interacción compleja de factores genéticos y ambientales. Objetivo: Determinar la posible asociación de los factores clínicos y ambientales con los niveles de anticuerpos antitiroideos y las pruebas de función tiroidea en la tiroiditis de Hashimoto. Métodos: Estudio observacional, descriptivo y transversal con 120 personas con diagnóstico de tiroiditis de Hashimoto. Variables estudiadas: edad, sexo, color de la piel, estado nutricional, paridad, hábito de fumar, consumo de alcohol, preparados estrogénicos, antecedentes familiares de enfermedad autoinmune tiroidea y personales de otras enfermedades autoinmunes. Se realizaron determinaciones de anticuerpos AbTPO, TSH, T3 y T4. Resultados: Predominio del sexo femenino (92,5 por ciento), de pacientes de piel blanca (50,8 por ciento) y con sobrepeso corporal (40 por ciento). El 73 por ciento no consumían preparados estrogénicos. El 20 por ciento tenían antecedentes familiares de enfermedad tiroidea y personales de diabetes mellitus tipo 1 (7,5 por ciento). La media del anticuerpo en pacientes con antecedentes de infecciones virales fue superior a los que no tuvieron este antecedente (732,6 vs. 624,6). El resto de las variables no mostraron diferencias entre las medias del anticuerpo. Ninguno de los factores estudiados mostró asociación con el estado de la función tiroidea. (p>0,05). Conclusiones: No existió asociación entre los factores clínicos y ambientales en relación a los niveles de Ac TPO y el estado de la función tiroidea, con predominio del hipotiroidismo manifiesto al diagnóstico de la TH(AU)

Introduction: Hashimoto's thyroiditis is a polygenic and multifactorial autoimmune thyroid disease, resulting from a complex interaction of genetic and environmental factors. Objective: To determine the possible association of clinical and environmental factors with antithyroid antibody levels and thyroid function tests in HT. Methods: An observational, descriptive, cross-sectional study was carried out with 120 subjects diagnosed with Hashimoto's thyroiditis. We studied variables such as age, sex, skin color, nutritional status, parity, smoking, alcohol consumption, estrogen preparations, family history of autoimmune thyroid disease and personal history of other autoimmune diseases. Additionally, AbTPO, TSH, T3 and T4 antibody determinations were made. Results: Predominance of the female sex (92.5 percent), white skin (50.8 percent) and body overweight (40 percent). 73 percent did not consume estrogenic preparations. Twenty percent had family history of thyroid disease and personal history of type 1 diabetes mellitus (7.5 percent). The mean antibody in patients with history of viral infections was higher than those without this history (732.6 vs. 624.6). The rest of the variables did not show differences between the means of the antibody. None of the factors studied showed association with the state of thyroid function. (p > 0.05). Conclusions: There was no association between clinical and environmental factors in relation to Ac TPO levels and the state of thyroid function, with a predominance of overt hypothyroidism at diagnosis of HT(AU)

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)

Función tiroidea y embarazo / Thyroid function and pregnancy

La enfermedad tiroidea, junto con la diabetes mellitus, son las dos endocrinopatías más frecuentes en el embarazo. El hipotiroidismo primario en mujeres en edad gestacional tiene una prevalencia del 2%, convirtiendo en un reto su diagnóstico, tratamiento y seguimiento en la práctica clínica

Thyroid disease, along with diabetes mellitus, are the two most common endocrinopathies in pregnancy. Primary hypothyroidism in women of gestational age has a prevalence of 2%, making its diagnosis, treatment and follow-up a challenge in clinical practice

Evaluación de la función tiroidea en el recién nacido pretérmino o de muy bajo peso / Assessment of thyroid function in the preterm and/or very low birth weight newborn

El Programa de cribado o detección precoz del hipotiroidismo congénito es uno de los mayores avances logrados en Pediatría. Las hormonas tiroideas son imprescindibles para el desarrollo y la maduración cerebral, que continúan en la etapa neonatal. Las alteraciones de la función tiroidea en niños prematuros y con bajo peso en los primeros meses de vida origina lesiones irreversibles en el sistema nervioso central y es una de las causas más frecuentes y evitables de retraso mental. El diagnóstico en el periodo neonatal es difícil, por lo que requiere estudio analítico para poder efectuar el tratamiento adecuado.La relevancia de este problema justifica su difusión a todas las áreas de Pediatría. El objetivo principal, evitar el daño cerebral en estos pacientes. Otros aspectos para optimizar el desarrollo adecuado de estos niños con todos los controles periódicos necesarios y lograr la inclusión del diagnóstico de las alteraciones tiroideas durante la estancia en unidades neonatales y en los primeros meses de vida precisan implementar los recursos de los centros sanitarios y continuar avanzando según los conocimientos actuales.En el presente documento nos centraremos en el cribado de los recién nacidos pretérmino (< 32 semanas de gestación) o con muy bajo peso para la edad gestacional (1.500-1.000 g muy bajo peso al nacer, o<1.000 g peso extremadamente bajo al nacer) y la protocolización de evaluación de función tiroidea en prematuros.Actualizamos los procedimientos diagnósticos, las pruebas imprescindibles y complementarias requeridas, la etiología y los diagnósticos diferenciales en esta patología. (AU)

The screening program or early detection of congenital hypothyroidism is one of the greatest advances achieved in Pediatrics. Thyroid hormones are essential for brain development and maturation, which continue into the neonatal stage. Alterations in thyroid function in premature and underweight children in the first months of life causes irreversible damage to the central nervous system and is one of the most frequent and avoidable causes of mental retardation. Diagnosis in the neonatal period is difficult, so it requires an analytical study to be able to carry out the appropriate treatment.The relevance of this problem justifies its communication to all areas of pediatrics. The main objective is to avoid brain damage in these patients. Other aspects to optimize the adequate development of these children with all the necessary periodic controls and to achieve the inclusion of the diagnosis of thyroid alterations during the stay in neonatal units and in the first months of life, need to implement the resources of the health centers and continue advancing according to current knowledge.In this document, we will focus on the screening of preterm newborns VLBW (<32 weeks of gestation) and/or very low weight for gestational age (1500-1000g VLBW or <1000g) and the function evaluation protocol thyroid in premature babies.We update the diagnostic procedures, the essential and complementary tests required, the etiology and the differential diagnoses in this pathology. (AU)

Assessment of thyroid function in the preterm and/or very low birth weight newborn.

The screening program or early detection of congenital hypothyroidism is one of the greatest advances achieved in Pediatrics. Thyroid hormones are essential for brain development and maturation, which continue into the neonatal stage. Alterations in thyroid function in premature and underweight children in the first months of life causes irreversible damage to the central nervous system and is one of the most frequent and avoidable causes of mental retardation. Diagnosis in the neonatal period is difficult, so it requires an analytical study to be able to carry out the appropriate treatment. The relevance of this problem justifies its communication to all areas of pediatrics. The main objective is to avoid brain damage in these patients. Other aspects to optimize the adequate development of these children with all the necessary periodic controls and to achieve the inclusion of the diagnosis of thyroid alterations during the stay in neonatal units and in the first months of life, need to implement the resources of the health centers and continue advancing according to current knowledge. In this document, we will focus on the screening of preterm newborns VLBW (<32 weeks of gestation) and/or very low weight for gestational age (1500-1000 g VLBW or <1000 g) and the function evaluation protocol thyroid in premature babies. We update the diagnostic procedures, the essential and complementary tests required, the etiology and the differential diagnoses in this pathology.

[Assessment of thyroid function in the preterm and/or very low birth weight newborn]. / Evaluación de la función tiroidea en el recién nacido pretérmino o de muy bajo peso.

The screening program or early detection of congenital hypothyroidism is one of the greatest advances achieved in Pediatrics. Thyroid hormones are essential for brain development and maturation, which continue into the neonatal stage. Alterations in thyroid function in premature and underweight children in the first months of life causes irreversible damage to the central nervous system and is one of the most frequent and avoidable causes of mental retardation. Diagnosis in the neonatal period is difficult, so it requires an analytical study to be able to carry out the appropriate treatment. The relevance of this problem justifies its communication to all areas of pediatrics. The main objective is to avoid brain damage in these patients. Other aspects to optimize the adequate development of these children with all the necessary periodic controls and to achieve the inclusion of the diagnosis of thyroid alterations during the stay in neonatal units and in the first months of life, need to implement the resources of the health centers and continue advancing according to current knowledge. In this document, we will focus on the screening of preterm newborns VLBW (<32 weeks of gestation) and/or very low weight for gestational age (1500-1000g VLBW or <1000g) and the function evaluation protocol thyroid in premature babies. We update the diagnostic procedures, the essential and complementary tests required, the etiology and the differential diagnoses in this pathology.

[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.

Historia de las pruebas de función tiroidea / History of thyroid function tests

El desarrollo de las pruebas de función tiroidea no ha sido fácil, con múltiples retos para mejorar algunas características que son insatisfactorias, incluso en la actualidad. En 1960 se logró la medición de tiroxina total (T4 total), y aunque fue un gran avance, los investigadores sabían que era insuficiente para una evaluación precisa de la función tiroidea. Uno de los problemas importantes radica en que existen diferencias marcadas interindividuales en la composición y en las cantidades de las proteínas de transporte de la T4 y la triyodotironina (T3). Por lo tanto, los depósitos de T4 y T3 son muy diferentes a los valores de T4 libre (T4L) y T3 libre (T3L). Por ejemplo, la mujer embarazada tiene el doble de globulina fijadora de tiroxina (TBG) y tres cuartas partes de la cantidad de albúmina que tenía cuando no estaba embarazada. También se pierde transtiretina y albúmina en enfermedades graves o con traumas, como quemaduras o sepsis. Entre 1963 y 1965 se desarrolló una prueba para tratar de obtener una estimación de la T4L, con el método de absorción de la hormona tiroidea a partir de la T4 total. Sin embargo, este análisis no funcionó correctamente, especialmente teniendo en cuenta la variabilidad en la TBG

Interpretación de las pruebas de función tiroidea / Interpretation of thyroid function tests

Los desórdenes de la glándula tiroides son comunes y pueden afectar hasta el 10% de la población en general. En muchas ocasiones los síntomas pueden ser inespecíficos, por lo que el médico en busca de un trastorno tiroideo debe llegar a un diagnóstico funcional y anatómico. Las mediciones séricas de las hormonas tiroideas confirman si hay un exceso, un déficit o si las concentraciones son normales. Para ello, se requiere un rango de referencia de la población local, y específicamente por grupos de edad, para una correcta interpretación de las pruebas de función tiroidea. Las hormonas tiroideas juegan un papel fundamental en el sistema endocrino, controlan el metabolismo general del cuerpo, el desarrollo neural, el crecimiento normal y la maduración de los huesos, así como funciones cardiovasculares y renales, entre otras. En esta revisión se pretende dar una aproximación a las pruebas tiroideas más relevantes, partiendo de la biosíntesis y secreción de las hormonas tiroideas, hasta llegar al abordaje para un diagnóstico inicial del paciente con trastorno tiroideo, mencionando los aspectos más importantes de los diferentes patrones tiroideos. El tratamiento detallado de cada uno de ellos, supera las expectativas de esta revisión

Thyroid gland disorders are common and can affect up to 10% of the general population. In many cases the symptoms can be nonspecific, so the physician in search for a thyroid disorder should reach a functional and anatomical diagnosis. Serum measurements of thyroid hormones confirm if there is an excess, a deficit, or if concentrations are normal. For this, reference ranges of the local population, and specifically by age groups, are required for a correct interpretation of thyroid function tests. Thyroid hormones play a fundamental role in the endocrine system, control of the general metabolism of the body, neural development, normal growth and maturation of bones, as well as in cardiovascular and renal functions, among others. In this review, the most relevant thyroid tests will be described, starting with the biosynthesis and secretion of thyroid hormones, and continuing with an approach to reach an initial diagnosis. Finally, the most important aspects of the different thyroid patterns will be mentioned. It is beyond the scope of this review, to describe the treatment for thyroid disorders.

[Prevalence and prognostic value of non-thyroidal illness syndrome among critically ill children]. / Prevalencia y valor pronóstico del síndrome del enfermo eutiroideo en niños críticos.

INTRODUCTION: Alterations in thyroid hormones during critical illness, known as non-thyroidal illness syndrome (NTIS), were suggested to have a prognostic value. However, pediatric data is limited. The aim of this study was to assess prevalence and prognostic value of NTIS among critically ill children. MATERIALS AND METHODS: A prospective observational study conducted on 70 critically ill children admitted into pediatric intensive care unit (PICU). Free triiodothyronine (FT3), free thyroxine (FT4), and thyroid stimulating hormone (TSH) were measured within 24hours of PICU admission. Primary outcome was 30-day mortality. RESULTS: NTIS occurred in 62.9% of patients but it took several forms. The most common pattern was low FT3 with normal FT4 and TSH (25.7% of patients). Combined decrease in FT3, FT4, and TSH levels occurred in 7.1% of patients. An unusual finding of elevated TSH was noted in three patients, which might be related to disease severity. Low FT4 was significantly more prevalent among non-survivors compared with survivors (50% versus 19.2%, P=.028). NTIS independently predicted mortality (OR=3.91; 95% CI=1.006-15.19; P=.0491). Concomitant decrease in FT3, FT4, and TSH was the best independent predictor of mortality (OR=16.9; 95% CI=1.40-203.04; P=.026). TSH was negatively correlated with length of PICU stay (rs=-0.35, P=.011). FT3 level was significantly lower among patients who received dopamine infusion compared with those who did not receive it (2.1±0.66 versus 2.76±0.91pg/mL, P=.011). CONCLUSION: NTIS is common among critically ill children and appears to be associated with mortality and illness severity.

Valor pronostico del hipotiroidismo en adultos mayores internados / Prognostic value of hypothyroidism in hospitalized elderly

INTRODUCCIÓN Mientras los niveles bajos de T3 han sido asociados con incremento de la mortalidad en pacientes con enfermedades no transmisibles (ENT), el impacto del hipotiroidismo manifiesto en su pronóstico es incierto. OBJETIVOS Definir las características de la función tiroidea de los pacientes adultos mayores hospitalizados y, a su vez, evaluar el papel del hipotiroidismo manifiesto en su evolución y pronóstico. MÉTODOS Se incluyó a todos los pacientes mayores de 60 años que habían sido ingresados al Servicio de Clínica Médica (n:451). Se excluyó a los pacientes ingresados a unidades de cuidados intensivos (UCI) y a otros servicios. RESULTADOS La población estudiada consistió en 243 mujeres (54%) y 208 hombres (46%) con una mediana de 77 años de edad. La causa principal de hospitalización fue respiratoria (18%), seguida de hematológica (15%). La prevalencia de antecedentes de enfermedad tiroidea fue del 17,5%. La mayoría de estos casos (96%) se debieron a hipotiroidismo anterior. Entre estos pacientes, la levotiroxina se interrumpió en el 18% de los casos en el primer día de hospitalización. Se clasificó como ENT (76%), hipotiroidismo severo (4%), hipotiroidismo subclínico (10%), hipertiroidismo subclínico (1%) y eutiroidismo (9%). Los pacientes clasificados como hipotiroidismo manifiesto eran en su mayoría añosos, requirieron pase a UCI y tuvieron mayor mortalidad comparados con los otros grupos. Los pacientes clasificados como hipotiroidismo manifiesto presentaron tasas más altas de mortalidad que los pacientes con ENT. No se observaron diferencias significativas en las tasas de mortalidad entre ENT y los pacientes con hipotiroidismo subclínico. DISCUSIÓN Los pacientes con hipotiroidismo manifiesto requirieron pase a UCI y tuvieron mayor mortalidad comparados con los otros grupos. A su vez, presentaron tasas más altas de mortalidad que los pacientes con ENT. No se observaron diferencias significativas en las tasas de mortalidad entre ENT y los pacientes con hipotiroidismo subclínico.

Thyroid function in pediatric population with different nutritional status / Función tiroidea en población pediátrica con diferente estado nutricional

Abstract: Background: Thyroid dysfunction has been associated with the development of obesity. There are few studies describing their status in Mexican schoolchildren, in whom obesity and subclinical hypothyroidism (SCH) prevail. Methods: Levels of stimulating thyroid hormone (TSH) and thyroid hormones (TH) were correlated with anthropometric variables as indicators of nutritional status in schoolchildren residents of Mexico City. The thyroid status and prevalences of SCH were compared between all the nutritional conditions, considering the degree of pubertal development. Results: The mean of TSH was 2.96 ± 1.48 mIU/L, and the prevalence of SCH was 11.30%. TSH levels are higher in prepubertal (5.21 ±1.24 mIU/L (95% confidence interval [CI]: 3.72-6.69) versus pubertal children (2.96 ± 1.48 mIU/L [95% CI: 2.61-3.30), as well as in children with obesity (3.5 ± 1.13 mIU/L [95% CI: 2.98-4.02]) versus normal weight children (2.43 ± 1.37 mIU/L [95% CI: 1.88 - 2.97]). The TH is similar in the whole population, although triiodothyronine total levels tend to be lower in malnourished children. There is a positive correlation between TSH levels and all anthropometric variables. The prevalences of SCH were higher in groups of children with overweight and obesity. Conclusions: The body fat content is associated with thyroid status in Mexican schoolchildren. In addition, it is relevant to consider the degree of pubertal development for diagnosing hyperthyrotropinemia in children and adolescents.

Resumen: Introducción: La disfunción tiroidea se ha asociado con el desarrollo de obesidad. Existen pocos estudios descritos en población escolar mexicana, en quienes prevalece la obesidad y el hipotiroidismo subclínico (HSC). Métodos: Los niveles de hormona estimulante de tiroides (TSH) y hormonas tiroideas (HT) se correlacionaron con variables antropométricas indicadoras del estado nutricional de niños escolares residentes de la Ciudad de México. El estado tiroideo y las prevalencias de HSC se compararon entre todas las condiciones nutricionales, considerando el grado de desarrollo puberal. Resultados: La media de TSH fue 2.96 ± 1.48 mUI/L, y la prevalencia de HSC fue de 11.30%. Los niveles de TSH fueron mayores en los niños prepúberes (5.21 ± 1.24 mUI/L [intervalo de confianza (IC) 95%: 3.72-6.69]) vs. los niños púberes (2.96 ± 1.48 mUI/L [IC 95%: 2.61-3.30); así como en los niños con obesidad (3.50 ± 1.13 mUI/L [IC 95%: 2.98-4.02]) vs. los niños con peso normal (2.43 ± 1.37 mUI/L [IC 95%: 1.88-2.97]). Los niveles de HT son similares en toda la población, aunque los niveles de triiodothyronine total (T3) tienden a ser menores en niños desnutridos. Existe correlación positiva entre los niveles de TSH y todas las variables antropométricas. Las prevalencias de HSC fueron mayores en los grupos de niños con sobrepeso y obesidad. Conclusiones: El contenido de grasa corporal está asociado con el estado tiroideo en escolares mexicanos. Adicionalmente, es relevante considerar el grado de desarrollo puberal para el diagnóstico adecuado de hipertirotropinemia en niños y adolescentes.

Thyroid function in pediatric population with different nutritional status.

Background: Thyroid dysfunction has been associated with the development of obesity. There are few studies describing their status in Mexican schoolchildren, in whom obesity and subclinical hypothyroidism (SCH) prevail. Methods: Levels of stimulating thyroid hormone (TSH) and thyroid hormones (TH) were correlated with anthropometric variables as indicators of nutritional status in schoolchildren residents of Mexico City. The thyroid status and prevalences of SCH were compared between all the nutritional conditions, considering the degree of pubertal development. Results: The mean of TSH was 2.96 ± 1.48 mIU/L, and the prevalence of SCH was 11.30%. TSH levels are higher in prepubertal (5.21 ±1.24 mIU/L (95% confidence interval [CI]: 3.72-6.69) versus pubertal children (2.96 ± 1.48 mIU/L [95% CI: 2.61-3.30), as well as in children with obesity (3.5 ± 1.13 mIU/L [95% CI: 2.98-4.02]) versus normal weight children (2.43 ± 1.37 mIU/L [95% CI: 1.88 - 2.97]). The TH is similar in the whole population, although triiodothyronine total levels tend to be lower in malnourished children. There is a positive correlation between TSH levels and all anthropometric variables. The prevalences of SCH were higher in groups of children with overweight and obesity. Conclusions: The body fat content is associated with thyroid status in Mexican schoolchildren. In addition, it is relevant to consider the degree of pubertal development for diagnosing hyperthyrotropinemia in children and adolescents.

Introducción: La disfunción tiroidea se ha asociado con el desarrollo de obesidad. Existen pocos estudios descritos en población escolar mexicana, en quienes prevalece la obesidad y el hipotiroidismo subclínico (HSC). Métodos: Los niveles de hormona estimulante de tiroides (TSH) y hormonas tiroideas (HT) se correlacionaron con variables antropométricas indicadoras del estado nutricional de niños escolares residentes de la Ciudad de México. El estado tiroideo y las prevalencias de HSC se compararon entre todas las condiciones nutricionales, considerando el grado de desarrollo puberal. Resultados: La media de TSH fue 2.96 ± 1.48 mUI/L, y la prevalencia de HSC fue de 11.30%. Los niveles de TSH fueron mayores en los niños prepúberes (5.21 ± 1.24 mUI/L [intervalo de confianza (IC) 95%: 3.72-6.69]) vs. los niños púberes (2.96 ± 1.48 mUI/L [IC 95%: 2.61-3.30); así como en los niños con obesidad (3.50 ± 1.13 mUI/L [IC 95%: 2.98-4.02]) vs. los niños con peso normal (2.43 ± 1.37 mUI/L [IC 95%: 1.88-2.97]). Los niveles de HT son similares en toda la población, aunque los niveles de triiodothyronine total (T3) tienden a ser menores en niños desnutridos. Existe correlación positiva entre los niveles de TSH y todas las variables antropométricas. Las prevalencias de HSC fueron mayores en los grupos de niños con sobrepeso y obesidad. Conclusiones: El contenido de grasa corporal está asociado con el estado tiroideo en escolares mexicanos. Adicionalmente, es relevante considerar el grado de desarrollo puberal para el diagnóstico adecuado de hipertirotropinemia en niños y adolescentes.

Discrepancia en concentraciones de hormonas tiroideas libres medidas por distintos inmunoensayos / Discrepancy in concentrations of free thyroid hormones measured by different immunoassays

Abstract: Thyroid function is assessed by measuring thyrotropin and free and total thyroid hormone concentrations. There are interferences with the results of immunoassays that can lead to an incorrect diagnosis, of which the most frequent are the binding of thyroid hormones to heterophile antibodies, rheumatoid factor, anti-Ruthenium antibodies, the intake of biotin and anti-streptavidin antibodies. We present three cases of clinically euthyroid patients, with normal TSH, high free T4 and T3, and normal total T4 and T3 performed in a Roche Diagnostics ® COBAS 8000 device. When the test was repeated on a Siemens® Immulite device, the free and total hormones were within normal ranges. In the Roche Diagnostics ® assay, the presence of biotin or anti-Ruthenium or anti-streptavidin antibodies interferes with the formation of the complex responsible for the emission of light that allows inferring concentrations of thyroid hormones. The Siemens test works differently since the emission of light depends on the binding of T4 to an antibody conjugated with alkaline phosphatase not participating in the process biotin, streptavidin or ruthenium so this interference is avoided. This possible interference in immunoassays should be taken into account in case clinical manifestations differ from these laboratory determinations, to avoid a diagnosis and potential inappropriate treatment.

Resumen: La función tiroidea se evalúa midiendo tirotropina y concentraciones de hormonas tiroideas libres y totales. Existen interferencias con los resultados de inmunoensayos que pueden llevar a un diagnóstico incorrecto, de ellas, las más frecuentes son la unión de hormonas tiroideas a anticuerpos heterófilos, el factor reumatoide, anticuerpos anti Rutenio, la ingesta de biotina y anticuerpos anti estreptavidina. Se presentan tres casos de pacientes clínicamente eutiroideos, con TSH normal, T4 y T3 libres elevadas, y T4 y T3 totales normales realizadas en un equipo COBAS 8000 de Roche Diagnostics®. Cuando se repitió el ensayo en un equipo Immulite de Siemens®, las hormonas libres y totales estaban dentro de rangos normales. En el ensayo de Roche Diagnostics ®, la presencia de biotina o anticuerpos anti Rutenio o anti estreptavidina, interfiere con la formación del complejo responsable de la emisión de luz que permite inferir las concentraciones de las hormonas tiroideas. El ensayo de Siemens funciona de manera diferente ya que la emisión de luz depende de la unión de la T4 a un anticuerpo conjugado con fosfatasa alcalina no participando en el proceso biotina, estreptavidina o Rutenio por lo que se evita esta interferencia. Esta posible interferencia en inmunoensayos debe ser tenida en cuenta en caso de que las manifestaciones clínicas difieran de estas determinaciones de laboratorio, para evitar un diagnóstico y potencial tratamiento inadecuado.

Hipotiroidismo y apnea del sueño / Hypothyroidism and sleep apnea

Resumen La salud es un derecho fundamental de todo ser humano, ya reconocido por la Ley Estatutaria de Salud (Ley 1751 de 2015). Esta ley devuelve la autonomía profesional al médico y para hacer buen uso de ella, debemos ejercer nuestra profesión dentro de un marco de autorregulación, ética, racionalidad y evidencia científica. Somos los médicos los llamados a liderar la identificación de los gastos innecesarios en salud, sin descuidar la calidad de la atención. Iniciamos aquí una serie de artículos en los que esperamos exponer, bajo evidencia científica, cuáles prácticas en medicina debemos continuar, mejorar o abolir con el fin de autorregularnos bajo conceptos éticos, de calidad y de racionalidad científica. El cuadro clínico del hipotiroidismo y de la apnea del sueño son bastantes similares, sin embargo cada una tiene unas características clínicas particulares que son las que debemos evaluar. ¿Se recomienda solicitar rutinariamente pruebas de función tiroidea a todos los pacientes con sospecha diagnóstica o diagnóstico confirmado de apnea del sueño?; ¿Se recomienda realizar un estudio del sueño a todos los pacientes con diagnóstico de hipotiroidismo clínico o subclínico?. No se recomienda realizar pruebas de función tiroidea a todos los pacientes con diagnóstico de apnea del sueño, así como tampoco hacer estudio del sueño a todos los pacientes con hipotiroidis-mo. Solo se recomienda hacer cuando la sospecha clínica lo amerite. Sugerimos la realización de investigaciones de costo/efectividad. (Acta Med Colomb 2016; 41: 138-140).

Abstract Health is a fundamental right of every human being, as recognized by the Statutory Health Law (Law 1751 of 2015). This law puts professional autonomy to the doctor, and to make good use of it we must exercise our profession within a framework of self-regulation, ethics, rationality and scientific evidence. We the physicians are the ones who are called to lead the identification of unnecessary health expenses without sacrificing quality of care. We begin here a series of articles in which we expect expose, on scientific evidence, which medical practices must we continue, improve or abolish in order to self-regulate us under ethical, quality and scientific rationality concepts. The clinical picture of hypothyroidism and sleep apnea are quite similar, yet each has unique clinical features that are what we have to assess. Is it recommended routinely request thyroid tests to all patients with suspected or confirmed diagnosis of sleep apnea?. Is it recommended to perform a sleep study to all patients diagnosed with clinical or subclinical hypothyroidism?. It is not recommended practice thyroid function tests to all patients diagnosed with sleep apnea, nor do sleep study to all patients with hypothyroidism. It is recommended only when the clinical suspicion warrants it. We suggest carry out cost / effectiveness research. (Acta Med Colomb 2016; 41: 138-140).