A potential role of activated NF-kappa B in the pathogenesis of euthyroid sick syndrome

Predictive value of thyroid function in severe aplastic anemia patients treated with immunosuppressive therapy

To explore the predictive value of thyroid function in severe aplastic anemia (SAA) patients treated with immunosuppressive therapy (IST), 149 SAA patients in our center were enrolled between February 2015 and June 2020 in this study. We assessed the thyroid function of 134 patients without primary thyroid diseases, and discovered that 89 patients were accompanied by abnormal thyroid hormone, especially low triiodothyronine (T3). Patients with higher pretreatment-free T3 (FT3) levels (>5 pmol/L) demonstrated superior response rates at 3 and 6 months after IST compared to those with lower FT3 levels (54.5% vs 35.4%, P = .020; 67.3% vs 46.9%, P = .020). Multivariate analysis indicated that shorter disease duration (≤56 days) and response at 6 months were independent favorable factors of overall survival (relative risk [RR] = 2.66, 95% confidence interval [CI] = 1.03-6.90, P = .040; RR = 30.10, 95% CI = 4.02-225.66, P = .001). The 6-year failure-free survival (FFS) was 53.8% (95% CI = 40.9%-65.1%). Multivariate analysis revealed that patients with a response at 6 months, shorter duration (≤56 days) and receiving rabbit antithymocyte globulin (ATG) had better FFS outcomes than those without a response at 6 months, with a longer duration and receiving porcine ATG (RR = 22.6, 95% CI = 7.9-64.9, P < .001; RR = 2.4, 95% CI = 1.3-4.5, P = .006; RR = 2.5, 95% CI = 1.1-5.8, P = .030). In conclusion, FT3 levels reflect the severity of SAA, and patients with higher FT3 levels (>5 pmol/L) had superior response rates than those with lower ones.

Prognostic role of euthyroid sick syndrome in MIS-C: results from a single-center observational study

Background

Euthyroid sick syndrome (ESS) is characterized by low serum levels of free triiodothyronine (fT3) with normal or low levels of thyroid stimulating hormone (TSH) and free thyroxine (fT4) and is reported in different acute clinical situations, such as sepsis, diabetic ketoacidosis and after cardiac surgery. Our aim was to evaluate the predicting role of ESS for disease severity in patients with Multisystem Inflammatory Syndrome in children (MIS-C).

Methods

A single-centre observational study on consecutive patients with MIS-C. Before treatment clinical, and laboratory data were collected and, in a subset of patients, thyroid function tests were repeated 4 weeks later. Variables distribution was analyzed by Mann-Whitney U-test and correlations between different parameters were calculated by Spearman's Rho coefficient.

Results

Forty-two patients were included and 36 (85.7%) presented ESS. fT3 values were significantly lower in patients requiring intensive care, a strong direct correlation was shown between fT3 and Hb, platelet count and ejection fraction values. A significant inverse correlation was retrieved between fT3 levels and C-reactive protein, brain natriuretic peptide, IL-2 soluble receptor and S-100 protein. Subjects with severe myocardial depression (EF < 45%) had lower fT3 values than subjects with higher EF. The thyroid function tests spontaneously normalized in all subjects who repeated measurement 4 weeks after admission.

Conclusion

ESS is a frequent and transient condition in acute phase of MIS-C. A severe reduction of fT3 must be considered as important prognostic factor for severe disease course, with subsequent relevant clinical impact in the management of these patients.

Association between psoriasis and thyroid function: results from the Brazilian Longitudinal Study of Adults Health (ELSA-Brasil)

Objective

To determine the relationship between psoriasis, thyroid-stimulating hormone (TSH), free thyroxine (FT4), free triodothyronine (FT3), thyroid peroxidase antibodies (TPOAb), and subclinical thyroid dysfunctions in middle-aged and older adults.

Materials and methods

Cross-sectional analyses included a self-reported medical diagnosis of psoriasis and thyroid function from the 3rd visit (2017-2019) of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). TSH, FT4, and FT3 levels were analyzed as continuous variables and quintiles, and TPOAb positivity and subclinical hypothyroidism as a yes/no variable. Logistic regression models were built as crude and adjusted by main confounders (age, sex, education level, race/ethnicity, and smoking).

Results

From 9,649 participants (52.3% women; 59.2 ± 8.7 years old), the prevalence of psoriasis was 2.8% (n = 270). TSH, FT4, TPOAb positivity, and subclinical hypothyroidism were not associated with psoriasis in the main analyses. In the stratified analysis, our findings showed positive associations of the lowest (OR = 2.01; 95% CI 1.05-3.84; p = 0.036) and the highest (OR = 2.13; 95% CI 1.12-4.05; p = 0.022) quintiles of FT4 and a protective association of TPOAb positivity (OR = 0.43; 95% CI 0.19-0.98; p = 0.046) with prevalent psoriasis in women. In the logistic regression for FT3, participants in the 1st quintile showed a statistically significant association with psoriasis for the whole sample (OR = 1.66; 95% CI 1.11-2.46; p = 0.013) and for men (OR = 2.25; 95% CI 1.25-4.04; p = 0.007) in the sex-stratified analysis.

Conclusions

The present study showed that the association of FT4 levels with psoriasis are different according to sex, with a possible U-shaped curve in women but not in men. Although there were some associations of FT3 with psoriasis, they may be a consequence of non-thyroidal illness syndrome. Further prospective data may clarify the association of thyroid function and psoriasis.

Fulminant Giant Cell Myocarditis vs. Lymphocytic Myocarditis: A Comparison of Their Clinical Characteristics, Treatments, and Outcomes

Objectives: Fulminant myocarditis (FM) is a rapidly progressive and frequently fatal form of myocarditis that has been difficult to classify. This study aims to compare the clinical characteristics, treatments and outcomes in patients with fulminant giant cell myocarditis (FGCM) and fulminant lymphocytic myocarditis (FLM).

Methods and Results: In our retrospective study, nine patients with FGCM (mean age 47.9 ± 7.5 years, six female) and 7 FLM (mean age 42.1 ± 12.3 years, four female) patients confirmed by histology in the last 11 years were included. Most patients with FGCM and FLM were NYHA functional class IV (56 vs. 100%, p = 0.132). Patients with FGCM had significantly lower levels of high-sensitivity C-reactive protein [hs-CRP, 4.4 (2.0–10.2) mg/L vs. 13.6 (12.6–14.6) mg/L, P = 0.004, data shown as the median with IQR], creatine kinase-myoglobin [CK-MB, 1.4 (1.0–3.2) ng/ml vs. 14.6 (3.0–64.9) ng/ml, P = 0.025, median with IQR], and alanine aminotransferase [ALT, 38.0 (25.0–61.5) IU/L vs. 997.0 (50.0–3,080.0) IU/L, P = 0.030, median with IQR] and greater right ventricular end-diastolic diameter (RVEDD) [2.9 ± 0.3 cm vs. 2.4 ± 0.6 cm, P = 0.034, mean ± SD] than those with FLM. No differences were observed in the use of intra-aortic balloon pump (44 vs. 43%, p = 1.000) and extracorporeal membrane oxygenation (11 vs. 43%, p = 0.262) between the two groups. The long-term survival rate was significantly lower in FGCM group compared with FLM group (0 vs. 71.4%, p = 0.022). A multivariate cox regression analysis showed the level of hs-CRP (hazard ratio = 0.871, 95% confidence interval: 0.761–0.996, P = 0.043) was an independent prognostic factor for FM patients. Furthermore, the level of hs-CRP had a good ability to discriminate between patients with FGCM and FLM (AUC = 0.94, 95% confidence interval: 0.4213–0.9964).

Conclusions: The inflammatory response and myocardial damage in the patients with FGCM were milder than those with FLM. Patients with FGCM had distinctly poorer prognoses compared with those with FLM. Our results suggest that hs-CRP could be a promising prognostic biomarker and a hs-CRP level of 11.71 mg/L is an appropriate cutoff point for the differentiating diagnosis between patients with FGCM and FLM.

High rates of (treated) hypothyroidism among chronic migraine patients consulting a specialized headache clinic: are we missing something?

BACKGROUND

Roughly three percent of episodic migraine patients evolve into the most burdensome chronic form of this condition every year. While some of the determinants behind this transformation are well established, others are still ill defined. Hypothyroidism is a prevalent endocrinological disorder that can both produce a secondary headache or aggravate a pre-existing primary headache disorder such as migraine.

OBJECTIVE

We aimed to re-assess the association between hypothyroidism and chronic migraine controlling for factors such as hormone replacement treatment status and bodyweight.

METHODS

We retrospectively analyzed the medical records of episodic and chronic migraine patients who consecutively consulted our headache clinic in order to determine the prevalence of adequately treated hypothyroidism in each group. Only patients receiving a stable dose regimen were included. The body mass index and other possibly confounding covariates were also collected.

RESULTS

Data from 111 migraine patients was included for analysis. Most (88.6%) of chronic migraine sufferers were overusing acute medication. Treated hypothyroidism was significantly more prevalent in chronic migraine patients (29.55%) compared to episodic migraine patients (8.96%). This association was independent of the patients' body mass index or other variables.

CONCLUSION

Alterations of neuronal metabolism, deficient calcitonin release, or focal inflammation causing local hormonal deactivation might explain why hypothyroidism, in spite of levothyroxine replacement therapy, is associated with migraine chronification. Further studies evaluating these factors are warranted.

The cytokine storm and thyroid hormone changes in COVID-19

BACKGROUND

COVID-19 is now a worldwide pandemic. Among the many extra-pulmonary manifestations of COVID-19, recent evidence suggested a possible occurrence of thyroid dysfunction.

PURPOSE

The Aim of the present review is to summarize available studies regarding thyroid function alterations in patients with COVID-19 and to overview the possible physio-pathological explanations.

CONCLUSIONS

The repercussions of the thyroid of COVID-19 seem to be related, in part, with the occurrence of a "cytokine storm" that would, in turn, induce a "non-thyroidal illness". Some specific cytokines and chemokines appear to have a direct role on the hypothalamus-pituitary-thyroid axis. On the other hand, some authors have observed an increased incidence of a destructive thyroiditis, either subacute or painless, in patients with COVID-19. The hypothesis of a direct infection of the thyroid by SARS-Cov-2 stems from the observation that its receptor, ACE2, is strongly expressed in thyroid tissue. Lastly, it is highly probable that some pharmaceutical agents largely used for the treatment of COVID-19 can act as confounding factors in the laboratory evaluation of thyroid function parameters.

Evaluation of Thyroid Function in Patients Hospitalized for Acute Heart Failure

BACKGROUND

Thyroid hormones (TH) are crucial for cardiovascular homeostasis. Recent evidence suggests that acute cardiovascular conditions, particularly acute heart failure (AHF), significantly impair the thyroid axis. Our aim was to evaluate the association of thyroid function with cardiovascular parameters and short- and long-term clinical outcomes in AHF patients.

METHODS

We performed a single-centre retrospective cohort study including patients hospitalized for AHF between January 2012 and December 2017. We used linear, logistic, and Cox proportional hazard regression models to analyse the association of thyroid-stimulating hormone (TSH) and free thyroxine (FT4) with inpatient cardiovascular parameters, in-hospital mortality, short-term adverse clinical outcomes, and long-term mortality. Two models were used: (1) unadjusted, and (2) adjusted for age and sex.

RESULTS

Of the 235 patients included, 59% were female, and the mean age was 77.5 (SD 10.4) years. In the adjusted model, diastolic blood pressure was positively associated with TSH [β = 2.68 (0.27 to 5.09); p = 0.030]; left ventricle ejection fraction (LVEF) was negatively associated with FT4 [β = -24.85 (-47.87 to -1.82); p = 0.035]; and a nonsignificant trend for a positive association was found between 30-day all-cause mortality and FT4 [OR = 3.40 (0.90 to 12.83); p = 0.071]. Among euthyroid participants, higher FT4 levels were significantly associated with a higher odds of 30-day all-cause death [OR = 4.40 (1.06 to 18.16); p = 0.041]. Neither TSH nor FT4 levels were relevant predictors of long-term mortality in the adjusted model.

CONCLUSIONS

Thyroid function in AHF patients is associated with blood pressure and LVEF during hospitalization. FT4 might be useful as a biomarker of short-term adverse outcomes in these patients.

High prevalence of non-thyroidal illness syndrome in patients at long-term care facilities

PURPOSE

Patients in acute care hospitals are often transferred to long-term care (LTC) when there is an expectation for a lengthy recovery. Prolonged non-thyroidal illness syndrome (NTIS) creates a state of hypothyroidism. We aimed to investigate the prevalence of NTIS in patients at LTC facilities.

METHODS

A cross-sectional study at University Hospitals and Rehabilitation and Skilled Nursing facility was performed. Four groups: control (n:33), intensive care unit (ICU) (n:34), long-term care hospital (LTCH) (n:50), and long-term care on chronic ventilatory support (LTCVS) (n:30). Serum levels of TSH, free T4 (FT4), free T3 (FT3), and interleukin 6 (IL6) measured at admission day in controls, within 48 h of admission in the intensive care group, between days 31 and 120 in the LTC hospital group and days 31 and 6 years in the LTC on chronic ventilatory support group.

RESULTS

Serum FT3 levels were lower in groups intensive care unit ICU, LTCH, and LTCVS than control. Low serum FT3 levels were observed in 80% ICU, 54% LTCH, 37% LTCVS, and 6% control patients. Low serum FT4 levels were observed in 32% ICU, 16% LTCH, and 20% LTCVS patients. Both low serum FT4 and FT3 levels were observed in 32% ICU, 16% LTCH, and 13% LTCVS patients. Serum IL6 and FT3 levels showed a negative correlation.

CONCLUSIONS

NTIS is highly prevalent in patients in LTC, creating a state of persistent hypothyroidism. The effects of thyroid hormone replacement in patients at LTC with non-thyroidal illness deserve further investigation.

Incidence of low-triiodothyronine syndrome in patients with septic shock

OBJECTIVE

Low levels of thyroid hormones have been associated with poor clinical outcomes. This metabolic situation, designated euthyroid sick syndrome, has been interpreted as a state of adaptation to different pathological processes, characterized by the decrease in plasma triiodothyronine. The present study seeks to determine the incidence of this disorder in patients with septic shock and its relationship with other severity indices and clinical outcomes.

METHODS

This prospective analytical study evaluated patients admitted to the intensive care unit with septic shock between April 2018 and July 2019. Variables associated with septic shock and thyroid profile were recorded at the time of the septic shock diagnosis and 7, 14, and 21 days later.

RESULTS

A total of 27 patients who met the inclusion criteria were analyzed. The incidence of an altered thyroid axis was 96.3%, with a mortality at 28 days of 36.7%. Patients without hormonal alteration did not present negative outcomes. Among those with low triiodothyronine, 42.3% recovered their thyroid function within 28 days, in whom mortality was 0%; 57.7% did not recover their thyroid function, in whom mortality was 66.7%. Those whose thyroid axis was altered and who did not normalize its function required more doses of vasoactives and had deteriorated lactate clearance.

CONCLUSION

Patients with septic shock have a high incidence of alteration of the thyroid axis, and this dysfunction is associated with higher mortality.

Thyroid hormones decrease the proinflammatory TLR4/NF-κβ pathway and improve functional parameters of the left ventricle of infarcted rats

Myocardial infarction leads to oxidative stress and promotes activation of the TLR4/NF-κβ proinflammatory pathway. Thyroid hormones (TH) are known to be cardioprotective after infarction. However, there are no studies evaluating whether TH could modulate this pathway in the heart. This study aimed to verify the effect of thyroid hormones on the TLR4/NF-κβ pathway after myocardial infarction. Male Wistar rats were allocated into the following groups: Sham-operated (SHAM), sham-operated + TH (SHAMT), infarcted (AMI) and infarcted + TH (AMIT). The treated rats received T4 and T3 (8 and 2 μg 100 g^-1 day^-1) for 12 days by gavage. Subsequently, the animals were evaluated by echocardiography and euthanized, and the left ventricle was collected for biochemical and molecular analyses. TH modulates TLR4/NF-κβ expression in the infarcted hearts of rats and decreases xanthine oxidase expression. These effects were related to cardiac functional improvement after infarction. The cardioprotective effects of T3 and T4 seem to involve an anti-inflammatory action.

Differences in the Plasma Proteome of Patients with Hypothyroidism before and after Thyroid Hormone Replacement: A Proteomic Analysis

Thyroid hormone is a potent stimulator of metabolism, playing a critical role in regulating energy expenditure and in key physiological mechanisms, such as growth and development. Although administration of thyroid hormone in the form of levo thyroxine (l-thyroxine) has been used to treat hypothyroidism for many years, the precise molecular basis of its physiological actions remains uncertain. Our objective was to define the changes in circulating protein levels that characterize alterations in thyroid hormone status. To do this, an integrated untargeted proteomic approach with network analysis was used. This study included 10 age-matched subjects with newly diagnosed overt hypothyroidism. Blood was collected from subjects at baseline and at intervals post-treatment with l-thyroxine until they reached to euthyroid levels. Plasma protein levels were compared by two-dimensional difference in gel electrophoresis (2D-DIGE) pre- and post-treatment. Twenty differentially expressed protein spots were detected. Thirteen were identified, and were found to be unique protein sequences by MALDI-TOF mass spectrometry. Ten proteins were more abundant in the hypothyroid vs. euthyroid state: complement C2, serotransferrin, complement C3, Ig κ chain C region, α-1-antichymotrypsin, complement C4-A, haptoglobin, fibrinogen α chain, apolipoprotein A-I, and Ig α-1 chain C region. Three proteins were decreased in abundance in the hypothyroid vs. euthyroid state: complement factor H, paraneoplastic antigen-like protein 6A, and α-2-macroglobulin. The differentially abundant proteins were investigated by Ingenuity Pathway Analysis (IPA) to reveal their associations with known biological functions. Their connectivity map included interleukin-6 (IL-6) and tumour necrosis factor α (TNF-α) as central nodes and the pathway identified with the highest score was involved in neurological disease, psychological disorders, and cellular movement. The comparison of the plasma proteome between the hypothyroid vs euthyroid states revealed differences in the abundance of proteins involved in regulating the acute phase response.

Diagnosis and management of treatment-refractory hypothyroidism: an expert consensus report

There is a frequently encountered subset of hypothyroid patients who are refractory to standard thyroid hormone replacement treatment and require unexpectedly high doses of levothyroxine. In addition to clinical situations where hypothyroid patients are non-compliant, or where there is the possibility of excipient-induced disease exacerbation (gluten/celiac disease), therapeutic failure may be due to impaired absorption of the administered drug. The common approach to managing patients with unusual thyroxine needs is to escalate the dose of levothyroxine until targeted TSH levels are achieved. This approach can increase the risk for prolonged exposure to supratherapeutic doses of levothyroxine, which increase the chances of adverse outcomes. Repeated adjustments of levothyroxine can also escalate the costs of treatment, as frequent office visits and laboratory tests are required to determine and maintain the desired dose. Clinicians should take a systematic approach to managing patients whom they suspect of having treatment-refractory hypothyroidism. This may include searching for, and adjusting, occult medical conditions and/or other factors that may affect the absorption of levothyroxine, before up-titrating the dose of traditional levothyroxine therapy. Depending on the underlying pathology, another approach that may be considered is to try alternative formulations of levothyroxine that are less susceptible to intolerance issues related to excipients, or, in some cases, to malabsorption. The early discovery of these factors via a thoughtful patient work-up may avoid unnecessary thyroid medication adjustments and their consequences for both patients and clinicians.

Prevalence of malnutrition-inflammation complex syndrome and its correlation with thyroid hormones in chronic haemodialysis patients

INTRODUCTION

Low levels of thyroid hormones, total triiodothyronine (T3) and free triiodothyronine (FT3) in haemodialysis patients is a marker of malnutrition and inflammation and are predictors of mortality. The aim of this study was to determine the prevalence of malnutrition-inflammation complex syndrome in haemodialysis and its relationship with the thyroid hormones thyrotropin, T3, FT3 and free thyroxine (FT4), as well as to evaluate the prevalence of low FT3 syndrome and its correlation with nutritional and inflammatory markers.

MATERIALS AND METHODS

Cross-sectional, analytical and comparative study that enrolled 128 haemodialysis patients: 50.8% females; mean age 45.05±17.01 years; mean time on haemodialysis 45.4±38.8 months; 29.7% diabetics; 79.7% with hypertension. Serum thyroid hormones thyrotropin, T3, FT3 and FT4 concentrations were measured and Malnutritition-Inflammation Score (MIS) was applie to diagnostic.

RESULTS

Mean thyroid hormone values were: thyroid hormones thyrotropin 2.48±1.8 mIU/ml (range: 0.015-9.5), T3 1.18±0.39 ng/ml (range 0.67-2.64), FT3 5.21±0.96pmol/l (range: 3.47-9.75); FT4 1.35±0.4 ng/ml (range: 0.52-2.57). Malnutrition-inflammation complex syndrome prevalence was 53.9%; 11.7% presented low FT3 levels. Serum T3 and FT3 concentrations inversely correlated with Malnutritition-Inflammation Score (MIS), while FT4 correlated positively with Malnutrition-Inflammation Score. In the linear regression analysis, low FT3 was associated with IL-6 (β= 0.265, p=.031), C-reactive protein (CRP) (β= -0.313, p=.018) and albumin (β= 0.276, p=.002).

CONCLUSION

Low T3 and FT3 levels are correlated with malnutrition and inflammation parameters. Malnutrition-inflammation complex syndrome can affect serum concentrations of thyroid hormones.

The ligand-bound thyroid hormone receptor in macrophages ameliorates kidney injury via inhibition of nuclear factor-κB activities

In chronic kidney disease (CKD) patients, inflammation plays a pivotal role in the progression of renal fibrosis. Hypothyroidism is associated with an increased occurrence of atherosclerosis and inflammation, suggesting protective roles of thyroid hormones and their receptors against inflammatory processes. The contribution of thyroid hormone receptors to macrophage differentiation has not been well documented. Here, we focused on the endogenous thyroid hormone receptor α (TRα) in macrophages and examined the role of ligand-bound TRα in macrophage polarization-mediated anti-inflammatory effects. TRα-deficient irradiated chimeric mice showed exacerbated tubulointerstitial injury in a unilateral ureteral obstruction model. Compared with wild-type macrophages, macrophages isolated from the obstructed kidneys of mice lacking TRα displayed increased expression of proinflammatory cytokines that was accompanied by enhanced nuclear translocation of p65. Comparison of TRα-deficient bone marrow-derived macrophages with wild-type macrophages confirmed the propensity of the former cells to produce excessive IL-1β levels. Co-culture of these macrophages with renal epithelial cells induced more severe damage to the epithelial cells via the IL-1 receptor. Our findings indicate that ligand-bound TRα on macrophages plays a protective role in kidney inflammation through the inhibition of NF-κB pathways, possibly by affecting the pro- and anti-inflammatory balance that controls the development of CKD.

Thyroid Hormone in the Pediatric Intensive Care Unit

Thyroid hormones are key factors necessary for normal growth and development in children. They have tight control of metabolic rate and, as a result, frequently become altered in their synthesis and/or release during times of stress or critical illness. Disturbances in thyroid hormone homeostasis have been well described in several pathologic states, including sepsis/septic shock, renal failure, trauma, severe malnutrition, and following cardiopulmonary bypass. Specifically, a decrease in serum triiodothyronine (T₃) and a concomitant increase in reverse triiodothyronine (rT₃) levels are the most common changes observed. It is further noteworthy that serum thyroxine (T₄), rT₃, and T₃ levels change in relation to severity of nonthyroidal illness. Many past investigators have speculated that these alterations are a teleological adaptation to severe illness and the increased metabolic demands that critical illness bears. However, this paradigm has been challenged through multiple avenues and has lost support over the past few years. Instead the "inflammatory hypothesis" has emerged implicating a cytokine surge as the mediator of thyroid hormone disruption. Overall, the demonstrated association between low thyroid hormone levels and poor clinical outcomes, the beneficial effects of thyroid hormone supplementation in multiple critically ill subpopulations, and the well-established safety profile of T₃ therapy make thyroid hormone supplementation in the pediatric ICU worth consideration.

Thyroid Hormones, Oxidative Stress, and Inflammation

Inflammation and oxidative stress (OS) are closely related processes, as well exemplified in obesity and cardiovascular diseases. OS is also related to hormonal derangement in a reciprocal way. Among the various hormonal influences that operate on the antioxidant balance, thyroid hormones play particularly important roles, since both hyperthyroidism and hypothyroidism have been shown to be associated with OS in animals and humans. In this context, the nonthyroidal illness syndrome (NTIS) that typically manifests as reduced conversion of thyroxine (T₄) to triiodothyronine (T₃) in different acute and chronic systemic conditions is still a debated topic. The pathophysiological mechanisms of this syndrome are reviewed, together with the roles of deiodinases, the enzymes responsible for the conversion of T₄ to T₃, in both physiological and pathological situations. The presence of OS indexes in NTIS supports the hypothesis that it represents a condition of hypothyroidism at the tissue level and not only an adaptive mechanism to diseases.

Accurate diagnosis of myalgic encephalomyelitis and chronic fatigue syndrome based upon objective test methods for characteristic symptoms

Although myalgic encephalomyelitis (ME) and chronic fatigue syndrome (CFS) are considered to be synonymous, the definitional criteria for ME and CFS define two distinct, partially overlapping, clinical entities. ME, whether defined by the original criteria or by the recently proposed criteria, is not equivalent to CFS, let alone a severe variant of incapacitating chronic fatigue. Distinctive features of ME are: muscle weakness and easy muscle fatigability, cognitive impairment, circulatory deficits, a marked variability of the symptoms in presence and severity, but above all, post-exertional “malaise”: a (delayed) prolonged aggravation of symptoms after a minor exertion. In contrast, CFS is primarily defined by (unexplained) chronic fatigue, which should be accompanied by four out of a list of 8 symptoms, e.g., headaches. Due to the subjective nature of several symptoms of ME and CFS, researchers and clinicians have questioned the physiological origin of these symptoms and qualified ME and CFS as functional somatic syndromes. However, various characteristic symptoms, e.g., post-exertional “malaise” and muscle weakness, can be assessed objectively using well-accepted methods, e.g., cardiopulmonary exercise tests and cognitive tests. The objective measures acquired by these methods should be used to accurately diagnose patients, to evaluate the severity and impact of the illness objectively and to assess the positive and negative effects of proposed therapies impartially.

The molecular basis of the non-thyroidal illness syndrome

The 'sick euthyroid syndrome' or 'non-thyroidal illness syndrome' (NTIS) occurs in a large proportion of hospitalized patients and comprises a variety of alterations in the hypothalamus-pituitary-thyroid (HPT) axis that are observed during illness. One of the hallmarks of NTIS is decreased thyroid hormone (TH) serum concentrations, often viewed as an adaptive mechanism to save energy. Downregulation of hypophysiotropic TRH neurons in the paraventricular nucleus of the hypothalamus and of TSH production in the pituitary gland points to disturbed negative feedback regulation during illness. In addition to these alterations in the central component of the HPT axis, changes in TH metabolism occur in a variety of TH target tissues during NTIS, dependent on the timing, nature and severity of the illness. Cytokines, released during illness, are known to affect a variety of genes involved in TH metabolism and are therefore considered a major determinant of NTIS. The availability of in vivo and in vitro models for NTIS has elucidated part of the mechanisms involved in the sometimes paradoxical changes in the HPT axis and TH responsive tissues. However, the pathogenesis of NTIS is still incompletely understood. This review focusses on the molecular mechanisms involved in the tissue changes in TH metabolism and discusses the gaps that still require further research.

Astrocyte Elevated Gene-1 (AEG-1) Contributes to Non-thyroidal Illness Syndrome (NTIS) Associated with Hepatocellular Carcinoma (HCC)

Non-thyroidal illness syndrome (NTIS), characterized by low serum 3,5,3'-triiodothyronine (T3) with normal l-thyroxine (T4) levels, is associated with malignancy. Decreased activity of type I 5'-deiodinase (DIO1), which converts T4 to T3, contributes to NTIS. T3 binds to thyroid hormone receptor, which heterodimerizes with retinoid X receptor (RXR) and regulates transcription of target genes, such as DIO1. NF-κB activation by inflammatory cytokines inhibits DIO1 expression. The oncogene astrocyte elevated gene-1 (AEG-1) inhibits RXR-dependent transcription and activates NF-κB. Here, we interrogated the role of AEG-1 in NTIS in the context of hepatocellular carcinoma (HCC). T3-mediated gene regulation was analyzed in human HCC cells, with overexpression or knockdown of AEG-1, and primary hepatocytes from AEG-1 transgenic (Alb/AEG-1) and AEG-1 knock-out (AEG-1KO) mice. Serum T3 and T4 levels were checked in Alb/AEG-1 mice and human HCC patients. AEG-1 and DIO1 levels in human HCC samples were analyzed by immunohistochemistry. AEG-1 inhibited T3-mediated gene regulation in human HCC cells and mouse hepatocytes. AEG-1 overexpression repressed and AEG-1 knockdown induced DIO1 expression. An inverse correlation was observed between AEG-1 and DIO1 levels in human HCC patients. Low T3 with normal T4 was observed in the sera of HCC patients and Alb/AEG-1 mice. Inhibition of co-activator recruitment to RXR and activation of NF-κB were identified to play a role in AEG-1-mediated down-regulation of DIO1. AEG-1 thus might play a role in NTIS associated with HCC and other cancers.

The relationship between deiodinase activity and inflammatory responses under the stimulation of uremic toxins

Background

It is unclear to what extent uremic toxins participate in inflammatory responses and the activities of deiodinases, as well as the effects of deiodinases on inflammatory cytokines.

Materials and methods

Hepatocellular carcinoma cell lines (HepG2) were transfected with small interfering ribonucleic acid (siRNA) specific for deiodinase type 1 (DIO1) and cultured with or without uremic toxins. The mRNA expression of DIO1, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α was detected by quantitative real-time PCR. The presence of selenoprotein M (SelM) and DIO1 was assessed by western blotting. Sonicate deiodinase activities in HepG2 cells were measured by a dithiothreitol-stimulated assay. The NF-κB, AP-1 and CREB-1 inflammatory signal pathways were confirmed by EMSA.

Results

After culturing for 24 h, the mRNA expression of DIO1 was significantly decreased by the specific siRNA (reduced by 76%, P = 0.0002). Uremic toxins significantly increased the mRNA expression (P < 0.01) of IL-1β, IL-6 and TNF-α and inhibited DIO1 mRNA expression (P < 0.01) compared with controls. Suppression of DIO1 by siRNA significantly decreased the mRNA expression of IL-1β and IL-6 (P < 0.05) but not TNF-α (P = 0.093). Uremic toxins and specific siRNA synchronously reduced the protein expression of SelM and DIO1.

Conclusions

Uremic toxins activate the expression of inflammatory cytokines. The major findings of this study indicate that the uremic toxins, more than inflammatory cytokines, play direct inhibitory roles in DIO1 enzyme activity, which then provides a negative feedback to the growing accumulation of inflammatory cytokines.

Is there a link between polycystic ovary syndrome and non-thyroidal illness syndrome?

OBJECTIVE

The aim of this study was to determine the frequency of non-thyroidal illness syndrome (NTIS) in patients with polycystic ovary syndrome (PCOS).

MATERIAL AND METHODS

During a 6-month period, 52 patients with PCOS were recruited for this cross-sectional study. The control group included 68 age-matched female volunteers. Serum free triiodothyronine (fT3), free thyroxine (fT4), thyroid stimulating hormone (TSH), anti-thyroperoxidase antibody (anti-TPO Ab), and anti-thyroglobulin antibody (anti-Tg Ab) were measured.

RESULTS

The TSH level in the PCOS patients and controls did not differ significantly (1.9±1.2 μIU/mL vs. 1.8±0.9 μIU/mL, p>0.05). Serum fT3 and fT4 levels in the controls were significantly lower than those in the PCOS patients (fT3: 2.7±0.3 pg/mL vs. 2.9±0.3 pg/mL, p=0.02; fT4: 1.0±0.1 ng/dL vs. 1.1±0.1 ng/dL, p=0.03). The Hs-CRP (high-sensitivity C-reactive protein) level in the PCOS patients was significantly higher than in the controls (3.5±4.9 mg/L vs. 1.7±2.7 mg/L, p=0.03). A statistically significant relationship was observed between Hs-CRP and fT4 (r=0.245, p=0.015). However, NTIS was not observed in either group.

CONCLUSION

Thyroid function abnormalities could be observed in PCOS; however, NTIS was not noted in the present study despite the inflammatory state of the PCOS patients.

A novel mechanism for the inhibition of type 2 iodothyronine deiodinase by tumor necrosis factor α: involvement of proteasomal degradation

Thyroxine (T₄) needs to be converted to 3,5,3'-triiodothyronine (T₃) by iodothyronine deiodinase to exert its biological activity. Recent studies revealed the presence of type 2 iodothyronine deiodinase (D2) in human thyroid tissue, human skeletal muscle and other tissues, suggesting that D2 is involved in maintaining plasma T₃ level in human. Tumor necrosis factor α (TNFα) is an inflammatory cytokine of which production is elevated in patients with nonthyroidal illness. Although several lines of evidence suggest the causal role of TNFα in nonthyroidal illness, detailed nature of the effect of TNFα on D2 remains unclear. In the present study, we identified D2 activity and D2 mRNA in TCO-1 cells, which were derived from human anaplastic thyroid carcinoma, and studied the mechanisms involved in the regulation of D2 expression by TNFα. The characteristics of the deiodinating activity in TCO-1 cells were compatible with those of D2 and Northern analysis demonstrated that D2 mRNA was expressed in TCO-1cells. D2 activity and D2 mRNA expression were rapidly increased by dibutyryl cAMP ((Bu)₂cAMP). TNFα showed an inhibitory effect on (Bu)₂cAMP-stimulated D2 activity in spite of little effect on (Bu)₂cAMP-stimulated D2 mRNA expression. MG132, a proteasome inhibitor abolished TNFα suppression of D2 activity whereas BAY11-7082 or 6-amino-4-(4-phenoxyphenylethylamino) quinazoline, inhibitors of nuclear factor-κB (NF-κB) failed to attenuate the effect of TNFα on D2 activity. These data suggest that a posttranslational mechanism through proteasomal degradation but not NF-κB activation is involved in the suppression of D2 by TNFα.

Pain and thyroid hormones

The role of endocrine systems in chronic pain mechanisms is slowly getting increasing experimental and clinical consideration. Many painful conditions appear to be directly and/or indirectly induced, reduced or, in some cases, modulated by hormones. We have done much work in trying to understand the relationship between hormones and pain, with particular attention to the hypothalamus-pituitary-gonadal axis. To expand our knowledge of this field, we have directed our attention to another axis, the hypothalamus-pituitary-thyroid (HPT). The literature on thyroid functions is vast but very few studies have focused on the HPT axis and pain. The few available data are considered in the present review to stimulate interest in the possible interactions between the HPT axis and pain.

Septic shock non-thyroidal illness syndrome causes hypothyroidism and conditions for reduced sensitivity to thyroid hormone

Non-thyroidal illness syndrome (NTIS) is part of the neuroendocrine response to stress, but the significance of this syndrome remains uncertain. The aim of this study was to investigate the effect of lipopolysaccharide (LPS)-induced NTIS on thyroid hormone (TH) levels and TH molecular targets, as well as the relationship between septic shock nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) activation and TH receptor β (THRB) gene expression at a multi-tissue level in a pig model. Prepubertal domestic pigs were given i.v. saline or LPS for 48 h. Serum and tissue TH was measured by chemiluminescence and RIA. Expression of THRs and cofactors was measured by real-time PCR, and deiodinase (DIO) activity was measured by enzyme assays. Tissue NF-kB nuclear binding activity was evaluated by EMSA. LPS-treated pigs had decreased TH levels in serum and most tissues. DIO1 expression in liver and kidney and DIO1 activity in kidney decreased after LPS. No changes in DIO2 activity were observed between groups. LPS induced an increase in hypothalamus, thyroid, and liver DIO3 activity. Among the other studied genes, monocarboxylate transporter 8 and THRB were the most commonly repressed in endotoxemic pigs. LPS-induced NF-kB activation was associated with a decrease in THRB gene expression only in frontal lobe, adrenal gland, and kidney cortex. We conclude that LPS-induced NTIS in pigs is characterized by hypothyroidism and tissue-specific reduced TH sensitivity. The role of NF-kB in regulating THRB expression during endotoxemia, if any, is restricted to a limited number of tissues.

Hypothyroidism and mortality among dialysis patients

BACKGROUND AND OBJECTIVES

Hypothyroidism is highly prevalent among ESRD patients, but its clinical significance and the benefits of thyroid hormone replacement in this context remain unclear.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study examined the association between hypothyroidism and all-cause mortality among 2715 adult dialysis patients with baseline thyrotropin levels measured between April of 2005 and April of 2011. Mortality was ascertained from Social Security Death Master Index and local registration systems. The association between hypothyroidism (thyrotropin greater than assay upper limit normal) and mortality was estimated using Cox proportional hazards models. To reduce the risk of observing reverse-causal associations, models included a 30-day lag between thyrotropin measurement and at-risk time.

RESULTS

Among 350 (12.9%) hypothyroid and 2365 (87.1%) euthyroid (assay within referent range) patients, 917 deaths were observed during 5352 patient-years of at-risk time. Hypothyroidism was associated with higher mortality. Compared with thyrotropin in the low-normal range (0.4-2.9 mIU/L), subclinical hypothyroidism (thyrotropin >upper limit normal and ≤10.0 mIU/L) was associated with higher mortality; high-normal thyrotropin (≥3.0 mIU/L and ≤upper limit normal) and overt hypothyroidism (thyrotropin >10.0 mIU/L) were associated with numerically greater risk, but estimates were not statistically significant. Compared with spontaneously euthyroid controls, patients who were euthyroid while on exogenous thyroid replacement were not at higher mortality risk, whereas patients who were hypothyroid were at higher mortality risk. Sensitivity analyses indicated that effects on cardiovascular risk factors may mediate the observed association between hypothyroidism and death.

CONCLUSIONS

These data suggest that hypothyroidism is associated with higher mortality in dialysis patients, which may be ameliorated by thyroid hormone replacement therapy.

An iodothyronine deiodinase from Chlamys farreri and its induced mRNA expression after LPS stimulation

Iodothyronine deiodinase is responsible for the deiodination of thyroxine T4 to T3, and involved in the complex neuroendocrine-immune regulatory network to optimize the immune response in vertebrate. In this study, the full-length cDNA of an iodothyronine deiodinase (designated as CfDx) was cloned from scallop Chlamys farreri. The complete cDNA sequence of CfDx was of 1404 bp and contained an open reading frame of 900 bp encoding a polypeptide of 299 amino acids. The deduced amino acid sequence of CfDx contained an in-frame TGA stop codon probably encoding an essential selenocysteine (SeC), and there was a conserved region of about 15 amino acids surrounding the SeC residue. The CfDx mRNA transcripts were detected in all the tested tissues, including haemocytes, hepatopancreas, kidney, adductor muscle, gonad, gill and mantle, with the higher expression level in hepatopancreas and kidney. After LPS stimulation, the CfDx mRNA expression level in haemocytes increased significantly at 12 h (25.35-fold, P < 0.05) and 24 h (7.62-fold, P < 0.05), and the concentration of T3 in haemolymph increased significantly at 12 h (3.62 ng dL(-1), P < 0.05) even the concentration of T4 did not change significantly. After scallop received an injection of 50 μg CfDx dsRNA, the expression level of CfDx mRNA in haemocytes began to decrease significantly at 36 h and maintained the relative low level (about 0.3-fold of the PBS control group) from 36 to72 h, but the ratio of T4/T3 in haemolymph began to increase at 36 h (2.31-fold, P < 0.05) and kept increasing from 36 to 72 h comparing with that in the PBS control group. These results indicated that CfDx was a homologue of iodothyronine deiodinase in scallop C. farreri, and it might be involved in the immunomodulation via regulating the concentration of thyroid hormones T3 and T4 in the haemolymph of scallop.

Forkhead box A1 (FOXA1) and A2 (FOXA2) oppositely regulate human type 1 iodothyronine deiodinase gene in liver

Type 1 iodothyronine deiodinase (D1), a selenoenzyme that catalyzes the bioactivation of thyroid hormone, is expressed mainly in the liver. Its expression and activity are modulated by several factors, but the precise mechanism of its transcriptional regulation remains unclear. In the present study, we have analyzed the promoter of human D1 gene (hDIO1) to identify factors that prevalently increase D1 activity in the human liver. Deletion and mutation analyses demonstrated that a forkhead box (FOX)A binding site and an E-box site within the region between nucleotides -187 and -132 are important for hDIO1 promoter activity in the liver. EMSA demonstrated that FOXA1 and FOXA2 specifically bind to the FOXA binding site and that upstream stimulatory factor (USF) specifically binds to the E-box element. Overexpression of FOXA2 decreased hDIO1 promoter activity, and short interfering RNA-mediated knockdown of FOXA2 increased the expression of hDIO1 mRNA. In contrast, overexpression of USF1/2 increased hDIO1 promoter activity. Short interfering RNA-mediated knockdown of FOXA1 decreased the expression of hDIO1 mRNA, but knockdown of both FOXA1 and FOXA2 restored it. The response of the hDIO1 promoter to USF was greatly attenuated in the absence of FOXA1. Taken together, these results indicate that a balance of FOXA1 and FOXA2 expression modulates hDIO1 expression in the liver.

Beyond low plasma T3: local thyroid hormone metabolism during inflammation and infection

Decreased serum thyroid hormone concentrations in severely ill patients were first reported in the 1970s, but the functional meaning of the observed changes in thyroid hormone levels, together known as nonthyroidal illness syndrome (NTIS), remains enigmatic. Although the common view was that NTIS results in overall down-regulation of metabolism in order to save energy, recent work has shown a more complex picture. NTIS comprises marked variation in transcriptional and translational activity of genes involved in thyroid hormone metabolism, ranging from inhibition to activation, dependent on the organ or tissue studied. Illness-induced changes in each of these organs appear to be very different during acute or chronic inflammation, adding an additional level of complexity. Organ- and timing-specific changes in the activity of thyroid hormone deiodinating enzymes (deiodinase types 1, 2, and 3) highlight deiodinases as proactive players in the response to illness, whereas the granulocyte is a novel and potentially important cell type involved in NTIS during bacterial infection. Although acute NTIS can be seen as an adaptive response to support the immune response, NTIS may turn disadvantageous when critical illness enters a chronic phase necessitating prolonged life support. For instance, changes in thyroid hormone metabolism in muscle during critical illness may be relevant for the pathogenesis of myopathy associated with prolonged ventilator dependence. This review focuses on NTIS as a timing-related and organ-specific response to illness, occurring independently from the decrease in serum thyroid hormone levels and potentially relevant for disease progression.

The association between thyroid hormones and arterial stiffness in peritoneal dialysis patients

BACKGROUND/AIMS

The association between thyroid hormones and arterial stiffness is unclear. In this study, we investigated, for the first time in a large cohort of euthyroid peritoneal dialysis patients, the relationship between thyroid hormone levels and arterial stiffness.

METHODS

Fifty-seven patients were enrolled. Serum TSH, free T3 and free T4 levels were measured by chemiluminescence immunoassay method. Pulse wave analysis [augmentation index (AIx) and subendocardial viability ratio (SEVR)] were measured to assess arterial stiffness.

RESULTS

Mean age was 49 ± 12.3 years, and 56.1% were female. Mean TSH, fT3 and fT4 levels were 1.97 ± 0.99 mIU/ml, 2.80 ± 0.42 pg/ml and 1.22 ± 0.16 ng/dl, respectively. Mean AIx and SEVR were 22.3 ± 11.3 and 136 ± 21%, respectively. AIx was negatively correlated with residual urine volume (r = -0.372, P: 0.03) and fT3 levels (r = -0.382, P: 0.005). SEVR was correlated only with TSH level (r = -0.394, P: 0.003). In linear regression analysis adjusted for age, gender, history of diabetes and cardiovascular disease and residual diuresis, fT3 level (t = -3.949, P < 0.001) remained associated with AIx. Only TSH level (t = -2.409, P: 0.02) was related to SEVR.

CONCLUSION

Low serum fT3 level is associated with arterial stiffness, and high TSH level within the normal range is related to lower SEVR in euthyroid PD patients.

The nonthyroidal illness syndrome in the non-critically ill patient

BACKGROUND

The nonthyroidal illness syndrome (NTIS) is a very common clinical entity among hospitalized patients and has been reported in practically every severe illness and acute or chronic stressful event. There is a large body of data associating the presence of NTIS with the severity of the underlying disease. Most of these studies concern intensive care unit (ICU) patients, whereas the non-critically ill patients outside the ICU setting are less well studied.

DESIGN

We provide a review of the existing literature focusing on studies examining NTIS in non-critically ill patients and attempt to summarize the pathophysiological pathways underlying the syndrome, its prognostic role, as well as the current intervention studies mainly from a clinical standpoint.

RESULTS

The aetiology of the NTIS is multifactorial and varies among different groups of patients. Experimental and clinical findings suggest that inflammatory cytokines are implicated in the pathogenesis of the syndrome, whereas recent evidence re-evaluate the role of deiodinases in thyroid hormone metabolism not only in the periphery but also in the hypothalamus and the pituitary and thus in the alterations accompanying NTIS. Clinical data examining the effectiveness of thyroid hormone supplementation in NTIS remain controversial.

CONCLUSIONS

As long as there is no clear evidence of benefit from thyroid hormone replacement and until well-designed studies confirm its efficacy, thyroxine supplementation should not be recommended for the treatment of NTIS.

Thyroid hormone receptors are down-regulated in skeletal muscle of patients with non-thyroidal illness syndrome secondary to non-septic shock

AIM

Non-thyroidal illness syndrome (NTIS) is related to changes in thyroid hormone (TH) physiology. Skeletal muscle (SM) plays a major role in metabolism, and TH regulates SM phenotype and metabolism. We aimed to characterize the SM of non-septic shock NTIS patients in terms of: i) expression of genes and proteins involved in TH metabolism and actions; and ii) NFKB's pathway activation, a responsible factor for some of the phenotypic changes in NTIS. We also investigated whether the patient's serum can induce in vitro the effects observed in vivo.

METHODS

Serum samples and SM biopsies from 14 patients with non-septic shock NTIS and 11 controls. Gene and protein expression and NFKB1 activation were analyzed by quantitative PCR and immunoblotting. Human SM cell (HSkMC) cultures to investigate the effects of patient's serum on TH action mediators.

RESULTS

Patients with non-septic shock NTIS showed higher levels of pro-inflammatory cytokines than controls. Expression of TRβ (THRB), TRα1 (THRA), and retinoid X receptor γ (RXRG) was decreased in NTIS patients. RXRA gene expression was higher, but its protein was lower in NTIS than controls, suggesting the existence of a post-transcriptional mechanism that down-regulates protein levels. NFKB1 pathway activation was not different between NTIS and control patients. HSkMC incubated with patient's serum increased TH receptor and RXRG gene expression after 48  h.

CONCLUSIONS

Patients with non-septic shock NTIS showed decreased expression of TH receptors and RXRs, which were not related to increased activation of the NFKB1 pathway. These findings could not be replicated in cultures of HSkMCs incubated in the patient's serum.

Clinical analysis on alteration of thyroid hormones in the serum of patients with acute ischemic stroke

Low T3 has been associated with increased short-term mortality in intensive care unit and long-term mortality in cardiovascular disease. The objective of this retrospective study is to investigate associations of thyroid hormone status with clinical severity and outcome in acute ischemic stroke, and whether there is association between the pituitary axis abnormality and the anterior/posterior circulation involvement. Patients with no history of thyroid abnormality who presented first ever stroke were studied. Total T3, T4, TSH levels, basic and clinical characteristics were collected and categorized. Neurological impairment was assessed using NIHSS and modified Rankin Scale. Twenty-nine patients (61%) had T3 ≤ 75 ng/dL. Low T3 group had significant higher NIHSS compared to normal T3 group. There was a significant negative correlation between T3 levels and NIHSS scores on admission. A significantly smaller percentage of patients with low T3 showed favorable neurological function improvement by both NIHSS and mRS measures compared to those with normal T3. There was no significant difference for anterior or posterior circulation involvement between low T3 and normal T3 groups. It is suggested that low T3 is associated with worse neurological outcome. The severity of low T3 may be a predictor of functional improvement in acute ischemic stroke.

Thyroid function in the critically ill newborn and child

PURPOSE OF REVIEW

Here we review typical thyroid function alterations observed in the critically ill pediatric patient.

RECENT FINDINGS

Abnormalities in the hypothalamic-pituitary-thyroid axis have recently been confirmed to be prevalent in similar proportions in pediatric and adult patients. Significant benefits of therapy have yet to be demonstrated.

SUMMARY

At present, there is no evidence of benefit in giving thyroid hormone to patients with nonthyroidal illness who have low serum T3 or T4 concentrations, including preterm infants and postcardiac surgery patients.

Selenium and thyroid hormone axis in critical ill states: an overview of conflicting view points

In critical ill states the plasma selenium levels are low and inversely correlated with the severity and outcome of the disease. The plasma selenium levels indicate the amount of circulating selenoproteins and selenoenzymes. These are important for the maintenance of the redox system, modulating the immune system and also for thyroid hormone metabolism. Not only all three deiodinases (D1-3) are selenoenzymes, but within the thyroid gland there are several other selenoenzymes, which are important for the maintenance of normal thyroid function. In critical ill states also triodothyronine (T3) is low and reverse T3 elevated, and also TSH and thyroxin (T4) are low, correlating like low plasma selenium with the severity of the disease. Subsequently, several intervention trials had been performed to evaluate whether an adjuvant selenium supplementation might attenuate the course of the disease and improve outcome. The selenium supplementation improved outcome and even reduced mortality in some but not all prospective randomized trials. A few prospective randomized intervention trials with selenium supplementation had also been performed to evaluate the hypothesis, whether low selenium is the cause of low-T3-syndrome, however, with conflicting results and no clear evidence that low D1 activity is due to the selenium deficiency in critical illness. Because D1 catalyses the conversion of T4 to T3 and also the clearance of reverse T3, low D1 activity would sufficiently explain low plasma T3 and elevated reverse T3. It had been, however, clearly shown that cytokines are responsible for the inhibition of D1 activity, but D2 and D3 are even higher during acute inflammation in critically ill patients. One of the most important effects of selenium on the immune system seems to be the reduction of cytokine release and therefore an indirect connection between low selenium and low D1 activity has to be postulated and not a lower D1 activity due to lower availability of selenium for the D1 expression.

Cellular and molecular basis of deiodinase-regulated thyroid hormone signaling

The iodothyronine deiodinases initiate or terminate thyroid hormone action and therefore are critical for the biological effects mediated by thyroid hormone. Over the years, research has focused on their role in preserving serum levels of the biologically active molecule T(3) during iodine deficiency. More recently, a fascinating new role of these enzymes has been unveiled. The activating deiodinase (D2) and the inactivating deiodinase (D3) can locally increase or decrease thyroid hormone signaling in a tissue- and temporal-specific fashion, independent of changes in thyroid hormone serum concentrations. This mechanism is particularly relevant because deiodinase expression can be modulated by a wide variety of endogenous signaling molecules such as sonic hedgehog, nuclear factor-kappaB, growth factors, bile acids, hypoxia-inducible factor-1alpha, as well as a growing number of xenobiotic substances. In light of these findings, it seems clear that deiodinases play a much broader role than once thought, with great ramifications for the control of thyroid hormone signaling during vertebrate development and metamorphosis, as well as injury response, tissue repair, hypothalamic function, and energy homeostasis in adults.

Thyroid hormone-mediated activation of the ERK/dual specificity phosphatase 1 pathway augments the apoptosis of GH4C1 cells by down-regulating nuclear factor-kappaB activity

Thyroid hormone (T3) plays a crucial role in processes such as cell proliferation and differentiation, whereas its implication on cellular apoptosis has not been well documented. Here we examined the effect of T3 on the apoptosis of GH4C1 pituitary cells and the mechanisms underlying this effect. We show that T3 produced a significant increase in apoptosis in serum-depleted conditions. This effect was accompanied by a decrease in nuclear factor-kappaB (NF-kappaB)-dependent transcription, IkappaBalpha phosphorylation, translocation of p65/NF-kappaB to the nucleus, phosphorylation, and transactivation. Moreover, these effects were correlated with a T3-induced decrease in the expression of antiapoptotic gene products, such as members of the inhibitor of apoptosis protein and Bcl-2 families. On the other hand, ERK but not c-Jun N-terminal kinase or MAPK p38, was activated upon exposure to T3, and inhibition of ERK alone abrogated T3-mediated apoptosis. In addition, T3 increased the expression of the MAPK phosphatase, dual specificity phosphatase 1 (DUSP1), in an ERK-dependent manner. Interestingly, the suppression of DUSP1 expression abrogated T3-induced inhibition of NF-kappaB-dependent transcription and p65/NF-kappaB translocation to the nucleus, as well as T3-mediated apoptosis. Overall, our results indicate that T3 induces apoptosis in rat pituitary tumor cells by down-regulating NF-kappaB activity through a mechanism dependent on the ERK/DUSP1 pathway.

Identification of molecular mechanisms related to nonthyroidal illness syndrome in skeletal muscle and adipose tissue from patients with septic shock

OBJECTIVE

Septic shock is one of various causes of nonthyroidal illness syndrome (NTIS). In humans, the molecular mechanisms involved in NTIS are mostly unknown. The aim of this study was to investigate, in patients with NTIS secondary to septic shock, changes in the expression of genes involved in the actions of thyroid hormones and in the activity of deiodinase enzymes, in two tissues important for protein and energy metabolism, skeletal muscle (SM) and subcutaneous adipose tissue (SAT).

DESIGN

Hospitalized patients were divided into a control and a septic shock NTIS group.

MEASUREMENT

Serum collection for biochemical measurements, and SM and SAT biopsies for mRNA expression analysis of thyroid hormone receptors (THRB1, THRA1), retinoid X receptors (RXRA, RXRB, RXRG), nuclear receptor corepressor (NCOR1), silencing mediator of retinoid and thyroid hormone receptor (SMRT), steroid receptor coactivator (SRC1), type 1 and 2 deiodinases (D1, D2), monocarboxylate transporter 8 (MCT8), SECIS binding protein 2 (SBP2) and uncoupling protein 3 (UCP3) as well as D1, D2 and D3 enzyme activity measurements.

RESULTS

The NTIS group had lower serum TSH, and free T3 and higher rT3 than controls. D1 and D3 were detected in SAT, with no differences found between the two groups; SM had very low D2 activity and again no differences were found between groups; D3 activity in SM was higher in NTIS than controls. SM expression of THRB1, RXRG and D2 was lower and RXRA higher in NTIS than controls. SAT from NTIS patients had lower MCT8, THRB1, THRA1, RXRG and SMRT, and higher UCP3 expression than controls.

CONCLUSIONS

In patients with septic shock NTIS tissue responses are orientated to decrease production and increase degradation (muscle) or decrease uptake (adipose tissue) of T3, as well as to decrease thyroid hormone actions.

Reawakened interest in type III iodothyronine deiodinase in critical illness and injury

Thyroid hormones influence gene expression in virtually all vertebrate tissues. Precise regulation of the active endogenous ligand, 3,5,3'-triiodothyronine (T(3)), is achieved by the sequential removal of iodine moieties from the thyroid hormone molecule. Type III iodothyronine deiodinase (D3) is the major inactivating enzyme terminating the action of T(3) and preventing activation of the prohormone, thyroxine (T(4)). Recent studies have revealed the induction of high D3 activity in diverse animal models of tissue injury including starvation, cryolesion, cardiac hypertrophy, infarction, and chronic inflammation. By analyzing serum and tissues taken from hospitalized patients at the time of death, investigators have also documented the robust induction of D3 activity in several human tissues that normally have none, including the liver and skeletal muscle, and shown clinically relevant consequences to systemic thyroid status. These studies reveal a novel role of D3 in the tissue response to injury and in the derangement of thyroid hormone homeostasis commonly observed during critical illness.

Metabolic support in sepsis and multiple organ failure: more questions than answers

The metabolic support of critically ill patients is a relatively new topic of active research and discussion, and surprisingly little is known about the effects of critical illness on metabolic physiology and activity. The metabolic changes seen in critical illness are highly complex, and how and when to treat them are only just beginning to be determined. Studies have demonstrated that the acute phase and the later phase of critical illness behave differently from a metabolic point of view for many organs, and while many of the alterations in metabolism seen during early critical illness may be appropriate and beneficial responses to cellular stress, whether this is true for all the metabolic alterations in all forms of critical illness is unclear. Currently we face more questions than answers, and further study is needed to elucidate the various components of the metabolic response to acute and chronic critical illness and to develop better techniques to assess and monitor these changes so that we can determine which therapeutic approaches should be used in what combinations and in which patients.

The nonthyroidal illness syndrome

This article briefly summarizes thyroid function alterations generally seen in the euthyroid sick syndrome, provides an overview of specific thyroidal adaptations during several clinical conditions and secondary to specific pharmacologic agents, and discusses the current controversy in thyroid hormone treatment of nonthyroidal illness.

Low triiodothyronine: a strong predictor of outcome in acute stroke patients

BACKGROUND

Low triiodothyronine (T3) has been associated with increased short-term mortality in intensive care unit patients and long-term mortality in patients with heart disease. The objective of this study was to investigate possible associations of thyroid hormone status with clinical outcome in patients admitted for acute stroke.

MATERIALS AND METHODS

A total of 737 consecutive patients with acute first ever stroke who presented within 24 h from symptoms' onset were studied. Total T3, thyroxin (T4) and thyroid-stimulating hormone (TSH) levels were assessed in the morning following admission. Cases with T3 values < or = 78 ng dL(-1) (1.2 nmol L(-1)) (median) were characterized as 'low T3'. Cases with T4 values < or = 4.66 microg dL(-1) (60 nmol L(-1)) were characterized as 'low T4'. Basic and clinical characteristics, stroke risk factors, and brain imaging were evaluated. Neurological impairment was assessed using the Scandinavian Stroke Scale.

RESULTS

Four hundred and seventeen (56%) patients had T3 values < or = 78 ng dL(-1) and 320 had normal T3 values. The 1-year mortality was 27.34% for low T3 and 19.37% for normal T3 cases (P = 0.006). A smaller percentage of patients with low T3 values were independent at 1 year compared to those with normal T3 values [54.2% vs. 68.7%, chi(2) = 12.09, P < 0.001, odds ratio (OR) = 0.53, 95% confidence interval (CI) 0.37-0.76]. Cox regression analysis revealed that increased age, haemorrhagic stroke, low Scandinavian Stroke Scale score, increased glucose and low T3 values (hazards ratio 0.69, CI = 0.48-0.98, P = 0.041) were significant predictors of 1-year mortality.

CONCLUSIONS

A high proportion of patients with acute stroke were found soon after the event with low T3 values. The low-T3 syndrome is an independent predictor of early and late survival in patients with acute stroke, and predicts handicap at 1 year.

Thyroid Function, Endothelium, and Inflammation in Hemodialyzed Patients: Possible Relations?

OBJECTIVE

Renal function affects the thyroid gland in many ways. Disturbances in hemostasis and inflammation are common complications of kidney diseases. Endothelial dysfunction may link these two processes.

DESIGN AND PATIENTS

A cross-sectional study on thyroid hormones in relation to markers of endothelial damage and inflammation in 96 hemodialyzed (HD) patients and 39 healthy volunteers was performed.

SETTING

The study took place in the dialysis unit at a university hospital.

INTERVENTION

Thyroid hormones, markers of endothelial damage (von Willebrand factor, thrombomodulin, intracellular adhesion molecule, and CD146), markers of inflammation (high-sensitivity C-reactive protein, tumor necrosis factor alpha), other hemostatic parameters (thrombin-antithrombin complexes, prothrombin fragments 1 + 2 - F1 + 2, plasmin-antiplasmin complexes, tissue plasminogen activator and its inhibitor, tissue factor pathway inhibitor, and platelet glycoprotein V) were measured using commercially available kits.

RESULTS

Free T3 and total T3 were lower in HD patients compared with controls. Markers of endothelial dysfunction and inflammation were significantly elevated in HD patients compared with controls. In multiple regression analysis T3 was independently related to time on dialyses, albumin, iron, ferritin, C-reactive protein (CRP), and F1 + 2 in HD patients. Free T3 was also independently related to total protein, total calcium, and triglycerides. In patients with CRP less than 6 mg/L in multiple regression analysis the only correlates of T3 were albumin and ferritin, whereas the only correlates of free T3 were albumin and time on dialyses. Multiple regression analysis showed that in HD patients with CRP greater than equal to 6 mg/L predictors of free T3 were CRP, F1 + 2, and dose of erythropoietin. In healthy volunteers T3 was related to tissue factor pathway inhibitor and platelet glycoprotein V was related to thyroid-stimulating hormone.

CONCLUSIONS

We described novel relations between thyroid hormones and markers of endothelial dysfunction and inflammation in HD patients. Thyroid dysfunction is related to time on dialyses, endothelial damage, and inflammatory state, frequently encountered in uremia. Therefore, the relations between thyroid axis and endothelium in HD subjects merit additional studies.

Thyroid function changes and cytokine alterations following major surgery

To establish whether cytokine release is implicated in thyroid hormone changes during surgical stress we studied 36 adult patients (20 men; mean age +/- SD: 68.5 +/- 10.5 years) undergoing elective major abdominal operations. We measured tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-8 and IL-10 and thyrotropin (TSH), free thyroxine (FT(4)) and triiodothyronine (T(3)) before scheduled non-emergency surgery, immediately postoperatively, on the 1st postoperative day (post-1) and on the 2nd postoperative day (post-2). TNF-alpha, IL-6 and IL-8 peaked on day post-1 whereas IL-10 peaked immediately postoperatively. Fourteen of 36 patients had low T(3) levels after surgery, indicating non-thyroidal illness (NTI). Significant negative correlations were noted among TNF-alpha, IL-6 and IL-8 against T(3) and FT(4). Cytokines are responsible, at least in part, for NTI following major operations.