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DEHAL1 (also named IYD) is the thyroidal enzyme that deiodinates mono- and diiodotyrosines (MIT, DIT) and recycles iodine, a scarce element in the environment, for the efficient synthesis of thyroid hormone. Failure of this enzyme leads to the iodotyrosine deiodinase deficiency (ITDD), characterized by hypothyroidism, compressive goiter and variable mental retardation, whose diagnostic hallmark is the elevation of iodotyrosines in serum and urine. However, the specific diagnosis of this type of hypothyroidism is not routinely performed, due to technical and practical difficulties in iodotyrosine determinations. A handful of mutations in the DEHAL1 gene have been identified as the molecular basis for the ITDD. Patients harboring DEHAL1 defects so far described all belong to consanguineous families, and psychomotor deficits were present in some affected individuals. This is probably due to the lack of biochemical expression of the disease at the beginning of life, which causes ITDD being undetected in screening programs for congenital hypothyroidism, as currently performed. This worrying feature calls for efforts to improve pre-clinical detection of iodotyrosine deiodinase deficiency during the neonatal time. Such a challenge poses questions of patho-physiological (natural history of the disease, environmental factors influencing its expression) epidemiological (prevalence of ITDD) and technical nature (development of optimal methodology for safe detection of pre-clinical ITDD), which will be addressed in this review.

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Introducción. Los programas para cribado neonatal utilizan muestras de sangre impregnada en papel, en ellas se determinan los marcadores de las patologías incluidas. La presencia de anticoagulantes en las muestras puede producir interferencias en los métodos de medida y se recomienda su no utilización. No es posible reconocer las muestras recogidas con anticoagulante. Material y métodos. Se desarrolló y optimizó un procedimiento por espectrometría de masas en tándem con electrospray (ESI-MS/MS) para la determinación de EDTA (ácido etilendiaminotetraacético) en las muestras de sangre en papel y se valoró su inclusión en el perfil de aminoácidos y acilcarnitinas utilizado para la detección precoz neonatal de enfermedades metabólicas. Se estudió su influencia sobre las medidas de tirotropina (TSH), realizadas para el cribado neonatal de hipotiroidismo congénito. Resultados. Se optimizaron los parámetros que permiten la medida de EDTA en el eluato de sangre. Se ha determinado TSH en sangre en papel, suero y plasma de un grupo de 110 muestras y EDTA en otro grupo de 2.300 muestras provenientes del programa de cribado neonatal detectando su presencia en un 0,74% de las mismas. Conclusiones. El método desarrollado es válido para la determinación de este anticoagulante y se puede incluir en el perfil de aminoácidos y acilcarnitinas por MS/MS para detectar aquellas muestras que se extrajeron inadecuadamente. Se ha confirmado la influencia negativa del EDTA en la determinación de TSH mediante un fluoroinmunoensayo (AutoDELFIA(R)). Esto podría provocar un falso negativo en el cribado neonatal de hipotiroidismo congénito (AU)

Introduction. Newborn screening programs use blood impregnated paper to analyze disease markers. The presence of EDTA in samples may interfere in the analytical methods used to measure these markers. For this reason, it is recommended not use anticoagulants in these samples. Moreover, it is not possible to recognize samples that have been collected into EDTA. Material and Methods. We developed and optimized an electrospray tandem mass spectrometry (ES-MS/MS) method to determine EDTA (ethylenediaminetetraacetic acid) in dried blood spots (DBS) on paper. We also included the method in the amino acids and acylcarnitines profile used for metabolic diseases neonatal screening. We also studied the EDTA influence on thyrotropin (TSH) neonatal screening analysis. Results. Optimized parameters for EDTA analysis in the blood eluate were found. TSH analysis was performed on DBS, serum and plasma samples from 110 patients. EDTA analysis on 2000 neonatal screening samples detected 0.74% of cases with EDTA contamination. Conclusions. The negative influence of EDTA in the determination of TSH by fluoroimmunoassay (AutoDELFIA(R)) has been confirmed. This could cause a false negative in neonatal screening for congenital hypothyroidism. The developed method is valid for the determination of this blood anticoagulant and can be included in the profile of amino acids and acylcarnitines by MS / MS to detect those samples that were taken improperly (AU)

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The effect of two sources of Se, selenized yeast (Se-Y) and sodium selenite, added to total mixed rations (TMR) fed to cows on Se milk content and distribution in milk components was studied on three farms for 6 weeks. The maximal increase in milk Se was attained with Se-Y supplemented at 0.3 microg g(-1). The effect was immediate, with an increase of 9 microg L(-1) being observed after only 5 days, and remained steady until the last sample at day 40 of Se supplementation. Se distribution in milk components was constant, 53.6, 42.6, and 9.3% in whey, casein, and fat, respectively, and was unaffected by the form of supplementation. The effect of the level of Se-Y supplementation on milk Se was studied on two farms. Increasing dietary Se-Y from 0 to 0.5 microg g(-1) elevated milk Se content from 20 to 39 microg L(-1). Se-enriched cow's milk at different levels can be produced by varying dietary Se supplementation in the form of selenized yeast.

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