Intervalos de referencia de hormonas tiroideas en mujeres gestantes mediante 2 inmunoanálisis diferentes: la importancia del método por encima de valores únicos universales, en consonancia con las recomendaciones internacionales 2017

Abstract

Background and objectivesThyroid dysfunction during pregnancy affects maternal and foetal health, which may influence the child's neurocognitive development. The thyroid physiology changes during pregnancy, requiring reference values (RV) to be established for each population and method. The objectives were to determine these thyroid hormone (TH) RV using 2 immunoassays and to estimate the nutritional status of iodine and the prevalence of thyroid autoimmunity in our population. Patients and methodsA total of 378 pregnant women from the health sectors of Zaragoza and Huesca, whose urinary iodine, antithyroid antibody and TH levels were assessed by 2different immunoassays (Beckman and Siemens), were enrolled. ResultsThe mean urinary iodine concentration was 187μg/l, with a median concentration of 146μg/l. From them, 78% took potassium iodide supplements and their consumption was related to higher levels of urinary iodine; 10.8% were positive for antithyroid peroxidase antibodies, 4.4% for anti-thyroglobulin antibodies, 2.4% for both and 4.1% for anti-TSHr. There was no association between urinary iodine and TSH or T4L. The reference values of TSH in the first trimester were Beckman: 0.2-4 and Siemens 0.2-3.4 mIU/l. ConclusionThe thyroid hormone reference values were markedly different from those proposed by the ATA-2011 guidelines but practically identical to those described in the Spanish population using the same immunoassays, as proposed by the ATA-2017 guidelines. Thyroid autoimmunity was similar to that published nationally and internationally. The mean and median urinary iodine levels are among the highest published in Spain to date and depend mainly on supplementation with potassium iodide to reach the WHO objectives, supporting the recommendations for supplementation with at least 150μg of iodine.