Relationship between the defining elements of the metabolic syndrome and thyroid function in subjects with euthyroid in population of Fortaleza

The association between clinically overt thyroid dysfunction and the development of metabolic disorders is well established. However, in recent years, the debate about the relationship between changes in thyroid function (TF), the metabolic syndrome (MS) or its components has gained special attention. Since the thyroid stimulating hormone (TSH) screening test more sensitive for detecting changes in TF, has been discussed more stringent criteria of normality in healthy individuals, from the finding of an association of adverse clinical outcomes with values previously considered normal. However, it is difficult to define "health", particularly in relation to body adiposity, whereas obesity is a condition of high prevalence itself linked to numerous illnesses. This study aimed to evaluate the relationship between the defining elements of MS and changes in the TF and determine the reference value (RV) of TSH in a sample of healthy subjects, from the stand point of thyroid, in the city of Fortaleza, Brazil. This is a cross-sectional study conducted from March 2009 to January 2010 which included 267 euthyroid subjects were selected from clinical and laboratory criteria. This team comprised four stages including the completion of a self-administered questionnaire, laboratorial and medical evaluation, with anthropometry, measurement of waist circumference (WC), systolic blood pressure (SBP) and diastolic (DBP), determination of serum TSH, free thyroxine ( FT4), triiodothyronine (T3), anti-thyroperoxidase (ATPO), thyroglobulin antibody (ATG), fasting glucose (FG), insulin, total cholesterol (TC), LDL, HDL and triglycerides (TG), insulin resistance calculated by homeostasis model assessment (HOMA-IR ), and the realization of thyroid ultrasound (TUS). Among the 267, 125 participants were selected, named individuals-reference, characterized by normal FT4, anti-thyroid antibody negative and normal TUS normal. This group composed the database of individual records necessary for determining the VR TSH according to the NCCLS and NACB guidelines. Data were subjected to statistical analysis (software Statistical Package for the Social Sciences (SPSS), versão 14.0 para Windows) being used the Student t test, Mann-Whitney test to compare continuous variables, the chi-square test for categorical variables and Spearman test for correlation analysis, adopting the statistical significance level of 5% (p < 0.05). Multiple linear regression models were applied to evaluate the associations between the FT with the concentrations of serum lipids and various traits of MS, with and without adjustment for age, sex, and HOMA-IR. To determine the reference range of TSH were adopted percentiles 2.5% and 97.5% of the distribution curve of the analyte, as the correspondents of the lower and upper limits of TSH RV. After the analysis, we observed that 77.2% of euthyroid subjects had at least one defining element of MS. Regarding the relationships between metabolic parameters and FT, there was positive correlation of TSH with only WC and DBP, while the FT4 correlated inversely with four (WC, FG, TG, DBP) in the five defining elements of MS. Yet been demonstrated a clear inverse correlation between the status of TF and HOMA-IR. From these findings, we speculate that in fact there is an association between the TF and MS, and that serum levels of thyroid hormones (THs) more than TSH, are related to cardiovascular risk factors. In determining the reference range of TSH, the values are between 0.56 to 4.45 mIU / l, which is in line with the points previously established in population-based studies.A associação entre disfunções tireoideanas clinicamente manifestas e o desenvolvimento de distúrbios metabólicos está bem determinada. Entretanto, nos últimos anos, o debate acerca da relação entre alterações na função tireoideana (FT) e a síndrome metabólica (SM), ou seus componentes, tem ganhado especial atenção. Sendo o hormônio tireoestimulante (TSH) o teste de rastreamento mais sensível para a detecção de alterações da FT, tem se discutido critérios mais rigorosos de normalidade em indivíduos sadios, a partir do achado de associação de desfechos clínicos desfavoráveis com valores anteriormente considerados normais. No entanto, torna-se difícil a definição de “saúde”, em especial no âmbito relacionado à adiposidade corporal, considerando ser a obesidade uma condição de elevada prevalência e per si relacionada a inúmeras morbidades. Assim, este trabalho objetivou avaliar a relação entre os elementos definidores da SM e a FT e determinar o valor de referência (VR) do TSH em uma amostra de indivíduos saudáveis, do ponto de vista tireoideano, residentes na cidade de Fortaleza-CE, Brasil. Trata-se de um estudo transversal conduzido no período de março de 2009 a janeiro de 2010 onde foram incluídos 267 indivíduos eutireoideanos, selecionados a partir de critérios clínicos e laboratoriais. Esta seleção compreendeu quatro etapas incluindo o preenchimento de um questionário auto-administrado, avaliação médica e laboratorial, com antropometria, medida da circunferência abdominal (CA), da pressão arterial sistólica (PAS) e diastólica (PAD), determinação sérica de TSH, tiroxina livre (T4l), triiodotironina (T3), anticorpo anti-tireoperoxidase (ATPO), anticorpo anti-tireoglobulina (ATG), glicose em jejum (GJ), insulina, colesterol total (CT), LDL, HDL e triglicerídeos (TG), cálculo da resistência à insulina, através do modelo de avaliação da homeostase (HOMA-IR), e a realização de ultrassonografia tireoideana (UST). Dentre os 267, foram selecionados 125 participantes, denominados indivíduos-referência, caracterizados por T4l e T3 normais, anticorpos anti-tireoideanos negativos e UST normal. Este grupo compôs o banco de registros individuais necessários para a determinação do VR do TSH de acordo com as recomendações do NCCLS e NACB guidelines. Os dados foram submetidos à análise estatística, através do software Statistical Package for the Social Sciences (SPSS), versão 14.0 para Windows, sendo usados o teste t de Student, teste de Mann-Whitney para comparação das variáveis contínuas, o teste do qui-quadrado para variáveis categóricas e o teste de Spearman para análise de correlações, sendo adotado o nível de significância estatística de 5% (p