Efeito da N-acetilcísteina sobre os níveis séricos dos hormônios tireoidianos na síndrome do T3 baixo

A Síndrome do T3 baixo refere-se a alterações nos níveis séricos dos hormônios tireoidianos, observado em pacientes criticamente doentes, na ausência de disfunção primária do eixo hipotálamo-hipófise-tireoide. Os indivíduos afetados apresentam baixos níveis de T3, elevação do T3 reverso (rT3), T4 normal ou baixo e TSH inapropriadamente normal ou baixo. Os mecanismos fisiopatológicos envolvidos são pouco conhecidos. No entanto, diversas alterações no metabolismo periférico dos hormônios tireoidianos são observadas nesta síndrome. Essa revisão discute os mecanismos fisiopatológicos envolvidos nas alterações dos hormônios tireoidianos na síndrome do T3 baixo e as alterações clínicas e prognósticas associadas.The Low T3 Syndrome refers to changes in serum levels of thyroid hormones observed in critically ill patients in the absence of primary dysfunction of the hypothalamic-pituitary-thyroid. Affected individuals have low levels of T3, rT3 elevated T4 and inappropriately normal TSH. The pathophysiological mechanisms are poorly understood. However, several changes in peripheral metabolism of thyroid hormones are seen in this syndrome. This review discusses the pathophysiological mechanisms involved in the alterations of thyroid hormones in low T3 syndrome and its clinical alterations and prognosis

Prevalência e implicações prognósticas da síndrome do T3 baixo em pacientes com sepse e choque séptico

A síndrome do T3 baixo refere-se a alterações dos níveis séricos dos hormônios tireoidianos em pacientes com doenças sistêmicas e ausência de disfunção primária do eixo hipotálamo-hipófise-tireoide. Sabe-se que os hormônios da tireoide têm função importante na adaptação metabólica à doença crítica e ao estresse, no entanto pacientes criticamente enfermos frequentemente apresentam redução dos níveis destes hormônios. As mudanças no metabolismo dos hormônios tireoidianos que ocorrem na fase aguda da doença crítica são consideradas benéficas, pois reduziriam o gasto energético e o consumo de proteínas, porém o aumento da morbidade e mortalidade associadas à síndrome do T3 baixo e a persistência de alterações na fase crônica da doença, em que o catabolismo é deletério, tem colocado em dúvida o caráter adaptativo dessas alterações. Dessa forma, o primeiro estudo dessa tese consiste em uma revisão sistemática e metanálise que avalia o prognóstico de pacientes internados em unidades de terapia intensiva que desenvolveram alterações dos hormônios tireoidianos. Essa revisão incluiu um total de 25 estudos e 3260 pacientes. A despeito de limitações na qualidade dos estudos incluídos, os resultados sugerem que alterações dos hormônios tireoidianos estão associados a pior desfecho em pacientes críticos. O segundo estudo dessa tese consiste em uma coorte que avaliou o influencia prognóstica da síndrome do T3 baixo em pacientes com sepse e choque séptico internados em unidade de terapia intensiva. O estudo demonstrou que a redução dos níveis séricos de T3 é preditor independente de mortalidade intra-hospitalar e evolução para doença crítica persistente nesta população.Nonthyroidal illness syndrome refers to alterations in serum thyroid hormones levels in patients with systemic diseases and absence of primary dysfunction of the hypothalamic-pituitary-thyroid axis. Thyroid hormones are known to play an important role in metabolic adaptation to critical illness and stress, however critically ill patients often present with reduced thyroid hormone levels. Changes in thyroid hormones metabolism that occur in the acute phase of critical illness are considered beneficial, as they would reduce energy expenditure and protein consumption, but the increase in morbidity and mortality associated with nonthyroidal illness syndrome and the persistence of changes in the chronic phase of disease, in which catabolism is harmful, cast doubt on the adaptive nature of these changes. Thus, the first study of this thesis consists of a systematic review and meta-analysis that assesses the prognosis of patients admitted to intensive care units who have developed changes in thyroid hormones. This review included a total of 25 studies and 6869 patients. Despite limitations in the quality of the included studies, our results suggest that changes in thyroid hormones are associated with a worse outcome in critically ill patients. The second study of this thesis consists of a cohort that evaluated the prognostic influence of non thyroidal illness syndrome in patients with sepsis and septic shock admitted to an intensive care unit. The study demonstrated that the reduction in serum T3 levels is an independent predictor of in-hospital mortality and progression to persistent critical illness in this population

Relationship among low T3 levels, type 3 deiodinase, oxidative stress, and mortality in sepsis and septic shock : defining patient outcomes

Low T3 syndrome occurs frequently in patients with sepsis. Type 3 deiodinase (DIO3) is present in immune cells, but there is no description of its presence in patients with sepsis. Here, we aimed to determine the prognostic impact of thyroid hormones levels (TH), measured on ICU admission, on mortality and evolution to chronic critical illness (CCI) and the presence of DIO3 in white cells. We used a prospective cohort study with a follow-up for 28 days or deceased. Low T3 levels at admission were present in 86.5% of the patients. DIO3 was induced by 55% of blood immune cells. The cutoff value of 60 pg/mL for T3 displayed a sensitivity of 81% and specificity of 64% for predicting death, with an odds ratio of 4.89. Lower T3 yielded an area under the receiver operating characteristic curve of 0.76 for mortality and 0.75 for evolution to CCI, thus displaying better performance than commonly used prognostic scores. The high expression of DIO3 in white cells provides a novel mechanism to explain the reduction in T3 levels in sepsis patients. Further, low T3 levels independently predict progression to CCI and mortality within 28 days for sepsis and septic shock patients

Non-thyroidal illness syndrome predicts outcome in adult critically ill patients : a systematic review and meta-analysis

We performed a systematic review and meta-analysis to comprehensively determine the prevalence and the prognostic role of non-thyroidal illness syndrome (NTIS) in critically ill patients. We included studies that assessed thyroid function by measuring the serum thyroid hormone (TH) level and in-hospital mortality in adult septic patients. Reviews, case reports, editorials, letters, animal studies, duplicate studies, and studies with irrelevant populations and inappropriate controls were excluded. A total of 6869 patients from 25 studies were included. The median prevalence rate of NTIS was 58% (IQR 33.2-63.7). In univariate analysis, triiodothyronine (T3) and free T3 (FT3) levels in non-survivors were relatively lower than that of survivors (8 studies for T3; standardized mean difference (SMD) 1.16; 95% CI, 0.41-1.92; I2 = 97%; P < 0.01). Free thyroxine (FT4) levels in non-survivors were also lower than that of survivors (12 studies; SMD 0.54; 95% CI, 0.31-0.78; I2 = 83%; P < 0.01). There were no statistically significant differences in thyrotropin levels between non-survivors and survivors. NTIS was independently associated with increased risk of mortality in critically ill patients (odds ratio (OR) = 2.21, 95% CI, 1.64-2.97, I2 = 65% P < 0.01). The results favor the concept that decreased thyroid function might be associated with a worse outcome in critically ill patients. Hence, the measurement of TH could provide prognostic information on mortality in adult patients admitted to ICU

A avaliação do risco de parto prematuro através da medida do colo uterino por ultrassonografia transvaginal

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