Antioxidants and methimazole in the treatment of Graves' disease: effect on urinary malondialdehyde levels

Regulation of the cellular redox state and the expression of DNA methyltransferase-1 in peripheral blood mononuclear cells from patients with Graves' disease

BACKGROUND

Graves' disease is an autoimmune disorder characterised by excessive production of thyroid hormones, which induces increased cellular metabolism in most tissues and increased production of reactive oxygen species (ROS). The aim of this work was to analyse the effect of ROS on cell viability and the expression of catalase (CAT), glutathione peroxidase-1 (GPx-1), superoxide dismutase (SOD-1) and DNA methyltransferase-1 (DNMT-1) in peripheral blood mononuclear cells (PBMC) from patients with newly diagnosed Graves' disease or treated with methimazole.

PATIENTS AND METHODS

For this study, women patients with newly diagnosed Graves' disease (n=18), treated with methimazole (n=6) and healthy subjects (n=15) were recruited. ROS were evaluated by flow cytometry, and the viability/apoptosis of PBMC was analysed by flow cytometry and fluorescence microscopy. Genomic expression of CAT, GPx-1, SOD-1 and DNMT-1 was quantified by real-time PCR.

RESULTS

We found high levels of ROS and increased expression of CAT, GPx-1, SOD-1 and DNMT-1 in PBMC from patients with newly diagnosed Graves' disease. Methimazole treatment reversed these parameters. Cell viability was similar in all study groups.

CONCLUSIONS

ROS induces the expression of CAT, GPx-1, and SOD-1. The activity of these enzymes may contribute to the protection of PBMC from the harmful effect of free radicals on cell viability. Increased expression of DNMT-1 may be associated with aberrant methylation patterns in immunoregulatory genes contributing to autoimmunity in Graves' disease.

Measurement of oxidative stress and total antioxidant capacity in hyperthyroid patients following treatment with carbimazole and antioxidant

Hyperthyroidism is a common endocrine disorder in which the thyroid produces too many hormones, resulting in the metabolism speed up. The present study was designed to measure oxidative stress and total antioxidant capacity in hyperthyroid patients following treatment with carbimazole and antioxidants supplements. This randomized clinical trial study was conducted to compare Malondialdehyde (MDA) and total antioxidant capacity (TAC) among 25 newly diagnosed hyperthyroid patients (Group A), 25 hyperthyroid patients treated with carbimazole (Group B) and 25 hyperthyroid patients treated with carbimazole and antioxidants supplement (Group C) of both sexes. In this study, the mean serum malondialdehyde (MDA) of the three groups were 4.60 ± 1.08 μmol/L (Group A), 2.79 ± 0.58 μmol/L (Group B), and 1.57 ± 0.29 μmol/L (Group C). We found the mean MDA level was significantly higher in Group A than Group B and Group C. This study found the MDA level was significantly higher in hyperthyroid patients treated with carbimazole alone (Group B, 2.79 ± 0.58 umol/L) than hyperthyroid patients treated with carbimazole and antioxidant combined (Group C, 1.57 ± 0.29 umol/L) among the study groups (p < 0.001). The results showed that the mean serum TAC was significantly lower in newly diagnosed hyperthyroid (Group A, 527.8 ± 78.44 umol/L] patients compared to carbimazole treated alone (Group B, 951.80 ± 99.67 umol/L) and combination with the antithyroid drug (carbimazole) and antioxidant treated (Group C, 1113.56 ± 121.69 umol/L). There was more improvement found in the treatment combined with the antithyroid drug (carbimazole) and antioxidant (Group C).

Conventional treatment of hyperthyroid patients significantly reduced oxidative stress and elevated serum TAC but not up to normal level. Therefore, the supplementation of antioxidants could be utilized to improve thyroid function in hyperthyroid patients by boosting antioxidants and restoring oxidant-antioxidant balance. However, further studies are required to determine the optimal dosage, route of administration, and timing of antioxidant therapy needed before this supplementation could be officially recommended as adjuvant therapy.

•

Antioxidant boosting with conventional treatment enhanced of thyroid function in hyperthyroidism.

•

Treating antioxidants and carbimazole enhanced thyroid function more than carbimazole alone.

•

MDA level was normalized along with improved TAC by treating antioxidants with the antithyroid drug.

•

Serum T4 significantly reduces and TSH significantly improves boosting antioxidant with carbimazole.

•

Antioxidant adding helps to improve thyroid hormone and oxidative damage of hyperthyroidism.

Management of Feline Hyperthyroidism and the Need to Prevent Oxidative Stress: What Can We Learn from Human Research?

Feline hyperthyroidism is a clinical syndrome related to an excessive production of thyroid hormones, and it is considered as a spontaneous animal model for human thyrotoxicosis. Many shared features between the feline and the human disease have been identified so far, including pathogenesis, clinical signs, and treatment options. Although methimazole is considered the first-choice drug in both species, several side effects have been described. Furthermore, methimazole could interfere with the oxidative status, already perturbated by the disease. It has been reported in humans that dietary management, mainly through antioxidant supplementation, could mitigate this oxidative burden. The purpose of the review is to describe current therapeutic options in the course of feline hyperthyroidism and to summarize the state of the art relationship between dietary antioxidants administration and the reduction of methimazole side-effects in humans to support the use of this approach also in cats.

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Thyroid hormones are necessary for the normal functioning of physiological systems. Therefore, knowledge of any factor (whether genetic, environmental or intrinsic) that alters the levels of thyroid-stimulating hormone (TSH) and thyroid hormones is crucial. Genetic factors contribute up to 65% of interindividual variations in TSH and thyroid hormone levels, but many environmental factors can also affect thyroid function. This review discusses studies that have analyzed the impact of environmental factors on TSH and thyroid hormone levels in healthy adults. We included lifestyle factors (smoking, alcohol consumption, diet and exercise) and pollutants (chemicals and heavy metals). Many inconsistencies in the results have been observed between studies, making it difficult to draw a general conclusion about how a particular environmental factor influences TSH and thyroid hormone levels. However, lifestyle factors that showed the clearest association with TSH and thyroid hormones were smoking, body mass index (BMI) and iodine (micronutrient taken from the diet). Smoking mainly led to a decrease in TSH levels and an increase in triiodothyronine (T3) and thyroxine (T4) levels, while BMI levels were positively correlated with TSH and free T3 levels. Excess iodine led to an increase in TSH levels and a decrease in thyroid hormone levels. Among the pollutants analyzed, most studies observed a decrease in thyroid hormone levels after exposure to perchlorate. Future studies should continue to analyze the impact of environmental factors on thyroid function as they could contribute to understanding the complex background of gene-environment interactions underlying the pathology of thyroid diseases.

Selenium in the Treatment of Graves' Hyperthyroidism and Eye Disease

Based on the role of oxidative stress in the pathogenesis of Graves' hyperthyroidism (GH) and Graves' Orbitopathy (GO), a therapy with the antioxidant agent selenium has been proposed and a number of studies have been performed, both in vitro and in vivo. In GH, reactive oxygen species (ROS) contribute to the thyroid and peripheral tissues damage. In GO, tissue hypoxia, as well as ROS, are involved in the typical changes that occur in fibroadipose orbital tissue and the perimysium of extraocular muscles. Antioxidants have been proposed to improve the effects of antithyroid drugs in GH patients, as well as the remodeling of orbital tissues in patients with GO. Here, we reviewed the literature on the possible beneficial effects and clinical use of selenium in the management of patients with GH and GO. A randomized clinical trial on the use of selenium in patients with mild GO provided evidence for a beneficial effect; no data are available on more severe forms of GO. Although the real effectiveness of selenium in patients with GH remains questionable, its use in the management of mild GO is generally believed to be beneficial, and selenium administration has been included in the clinical practice for the patients with mild eye disease.

Oxidative Stress in Graves Disease and Graves Orbitopathy

Oxidative stress is involved in the pathogenesis of Graves hyperthyroidism (GH) and Graves orbitopathy (GO) and an antioxidant approach has been proposed for both. In GH, a disbalance of the cell redox state is associated with thyroid hyperfunction and antithyroid medications may reduce oxidative stress. Tissue hypoxia participates in the pathogenesis of GO, and oxygen free radicals are involved in the typical changes of orbital tissues as reported by in vitro and clinical studies. Antioxidant agents, especially selenium, have been proposed as a therapeutic option for GH and GO. A clinical study regarding the use of selenium in mild GO has provided evidence for a beneficial effect in the short term, even though its beneficial effects in the long term are still to be investigated. In addition to selenium, a protective role of other antioxidant agents, i.e., quercetin, enalapril, vitamin C, N-acetyl-L-cysteine and melatonin has been suggested by in vitro studies, although clinical studies are lacking. Here, we review the role of oxidative stress and antioxidant agents in GH and GO.

Challenges and perspectives of selenium supplementation in Graves' disease and orbitopathy

PURPOSE

This review focuses on the results of prospective randomized clinical trials and the conclusions from respective meta-analyses in order to summarize experiences with adjuvant selenium (Se) supplementation in Graves' hyperthyroidism and orbitopathy, while identifying ambiguous findings and highlighting important open research issues.

METHODS

We searched the PubMed and the Cochrane Central Register of Controlled Trials (CENTRAL) through May 31, 2019, for relevant studies.

RESULTS

The available evidence concerning routine use of Se in the treatment of Graves' hyperthyroidism remains ambiguous. Results of meta-analyses, including ten RCTs, suggest that adjuvant Se supplementation can enhance the restoration of biochemical euthyroidism. Unfortunately, these results must be judged cautiously owing to several important limitations. Moreover, an in-depth analysis of relevant long-term clinical measures of therapeutic success (such as remission rate after antithyroid drug treatment), besides surrogate markers (for example, hormone or autoantibody concentrations), is generally missing. Based on a single study, Se supplementation is recommended in patients with mild orbitopathy of short duration because it may decrease inflammation and eye-specific symptoms while also achieving a marked improvement in disease-specific quality of life. The effects of Se supplementation on moderate-to-severe orbitopathy remain as yet unknown.

CONCLUSIONS

Additional randomized clinical trials with clinically relevant endpoints are urgently needed to further aid in clinical decision-making, including better stratification of Graves' disease patients, who are most likely to benefit from Se supplementation.

Redox unbalance in the hyperthyroid cat: a comparison with healthy and non-thyroidal diseased cats

Background

Feline hyperthyroidism, the most common endocrinopathy in older cats, provides a spontaneous model for human thyrotoxicosis. Human thyrotoxicosis is associated with redox unbalance, which may result in organ damage. The redox status of hyperthyroid cats is largely unknown. The aims of the present study were to compare the redox status of cats with hyperthyroidism with that of healthy cats and cats with chronic non-thyroidal illness.

Results

Forty cats with untreated hyperthyroidism (group H), 45 chronically ill cats with non-thyroidal illness (group I), and 39 healthy cats (group C) were recruited for this observational cross-sectional study. All cats were screened for redox status markers. Determinable reactive oxygen metabolites (d-ROMs) were used as oxidative stress markers. Antioxidant status was determined using the OXY-Adsorbent test to quantify the plasma barrier to oxidation. The Oxidative Stress index (OSi) was calculated as the ratio of d-ROMs and OXY-Adsorbent test values. Data were compared by ANOVA with Tukey’s multiple comparisons post-hoc test. The dROMs of group H (193 ± 47 CarrU) were significantly higher (p &lt; 0.001) than those of the healthy cats (103 ± 17 CarrU). The OXY-Adsorbent test results in group H (265 ± 68 μmol HClO/ml) were significantly lower than those in healthy cats (390 ± 83 μmol HClO/ml; p &lt; 0.01) and chronically ill cats (306 ± 45 μmol HClO/ml, p &lt; 0.05). Moreover, the Osi value in group H (0.8 ± 0.2 CarrU/μmol HClO/ml) was significantly higher (p &lt; 0.001) than that of the healthy cats (0.3 ± 0.1 CarrU/μmol HClO/ml).

Conclusions

As described in humans with hyperthyroidism, feline hyperthyroidism is associated with redox unbalance. Free radical production is increased in hyperthyroid cats and their antioxidant depletion seems to be more severe than in cats with non-thyroidal illnesses. Our results support the rationale for a clinical trial investigating the potential positive effects of antioxidant supplementation to cats with hyperthyroidism.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-1896-7) contains supplementary material, which is available to authorized users.

Selenium in Graves Hyperthyroidism and Orbitopathy

PURPOSE

To review the in vitro and in vivo studies supporting a role of selenium for the treatment of mild Graves orbitopathy.

METHODS

Review of the current literature on the role of selenium in the management of Graves orbitopathy.

RESULTS

Graves orbitopathy (GO) is a disfiguring and disabling disorder usually observed in patients with Graves hyperthyroidism, and more rarely in patients with hypothyroid autoimmune thyroiditis or in the absence of overt thyroid dysfunction. Noninvasive treatments include intravenous glucocorticoids and orbital radiotherapy and are generally offered to patients with moderately severe GO. In contrast, patients with mild GO are generally treated only with local measures. Thus, the benefits of intravenous glucocorticoids in mild GO are limited and do not justify the risks that the treatment carries. However, a medical treatment for mild GO is heavily wanted, as a relevant proportion of patients have a significant decrease in their quality of life, and GO can progress into more severe forms. Because of the role of oxidative stress in the pathogenesis of GO, an antioxidant approach has been proposed and the antioxidant agent selenium has been shown to be effective for GO.

CONCLUSION

Studies have shown that a 6-month course of sodium selenite can improve the course of mild GO and prevent deterioration when compared with placebo.

Effects of selenium on short-term control of hyperthyroidism due to Graves' disease treated with methimazole: results of a randomized clinical trial

OBJECTIVE

In spite of previous conflicting results, an adjuvant role of selenium in the treatment of Graves' disease (GD) hyperthyroidism has been proposed. To address this issue, a randomized clinical trial was carried out aimed at investigating whether selenium is beneficial on the short-term control of GD hyperthyroidism treated with methimazole (MMI).

METHODS

Thirty newly diagnosed hyperthyroid GD patients were randomly assigned to treatment with: (i) MMI or (ii) MMI plus selenium. Primary outcomes were: control of hyperthyroidism and clinical and biochemical manifestations of hyperthyroidism [heart rate, cholesterol, sex hormone-binding globulin (SHBG), hyperthyroidism symptoms] at 90 days.

RESULTS

Baseline features of the two groups did not differ. Serum selenium at baseline was similar in the two groups and within the recommended range to define selenium sufficiency. Selenium increased with treatment in the MMI-selenium group and became significantly higher than in the MMI group. Serum malondialdehyde, a marker of oxidative stress, was similar in the two groups and decreased significantly with treatment, with no difference between groups. Administration of MMI was followed by a reduction of FT₃ and FT₄, with no difference between groups. Heart rate, SHBG and symptoms of hyperthyroidism decreased, whereas total cholesterol increased in both groups with no difference between groups.

CONCLUSIONS

Our study, carried out in a selenium-sufficient cohort of GD patients, failed to show an adjuvant role of selenium in the short-term control of hyperthyroidism. However, selenium might be beneficial in patients from selenium-deficient areas, as well as in the long-term outcome of antithyroid treatment.

Relapse prediction in Graves´ disease: Towards mathematical modeling of clinical, immune and genetic markers

PROBLEM

Graves' disease (GD) is an important and prevalent thyroid autoimmune disorder. Standard therapy for GD consists of antithyroid drugs (ATD) with treatment periods of around 12 months but relapse is frequent. Since predictors for relapse are difficult to identify the individual decision making for optimal treatment is often arbitrary.

METHODS

After reviewing the literature on this topic we summarize important factors involved in GD and with respect to their potential for relapse prediction from markers before and after treatment. This information was used to design a mathematical model integrating thyroid hormone parameters, thyroid size, antibody titers and a complex algorithm encompassing genetic predisposition, environmental exposures and current immune activity in order to arrive at a prognostic index for relapse risk after treatment.

CONCLUSION

In the search for a tool to analyze and predict relapse in GD mathematical modeling is a promising approach. In analogy to mathematical modeling approaches in other diseases such as viral infections, we developed a differential equation model on the basis of published clinical trials in patients with GD. Although our model needs further evaluation to be applicable in a clinical context, it provides a perspective for an important contribution to a final statistical prediction model.

N-Acetylcysteine affects obesity-related protein expression in 3T3-L1 adipocytes

OBJECTIVES

Oxidative stress plays critical roles in the pathogeneses of diabetes, hypertension, and atherosclerosis, but its effect on fat accumulation is still unclear. In this study, we analyzed the role of the well-known antioxidant and a glutathione (GSH) precursor N-acetylcysteine (NAC) in fat accumulation and the expression of obesity-associated proteins.

METHODS

We studied the effects of 10 µM NAC on obesity-related protein expression in cultured 3T3-L1 preadipocytes, which are able to differentiate into mature adipocytes and accumulate lipids.

RESULTS

NAC treatment inhibited fat accumulation and reduced the expression of obesity-related proteins, including monoamine oxidase A, heat shock protein 70 (HSP70), aminoacylase -1 (ACY-1), and transketolase.

DISCUSSION

Our results suggest that the effects of NAC on triglycerides (Tgs) and protein expression are correlated. In support of this, we showed that NAC treatment affected both the Tg synthesis pathway and the expression levels of proteins implicated in human obesity.

Selenium and the thyroid gland: more good news for clinicians

The thyroid is the organ with the highest selenium content per gram of tissue because it expresses specific selenoproteins. Since the discovery of myxoedematous cretinism and thyroid destruction following selenium repletion in iodine- and selenium-deficient children, data on links between thyroid metabolism and selenium have multiplied. Although very minor amounts of selenium appear sufficient for adequate activity of deiodinases, thus limiting the impact of its potential deficiency on synthesis of thyroid hormones, selenium status appears to have an impact on the development of thyroid pathologies. The value of selenium supplementation in autoimmune thyroid disorders has been emphasized. Most authors attribute the effect of supplementation on the immune system to the regulation of the production of reactive oxygen species and their metabolites. In patients with Hashimoto's disease and in pregnant women with anti-TPO antibodies, selenium supplementation decreases anti-thyroid antibody levels and improves the ultrasound structure of the thyroid gland. Although clinical applications still need to be defined for Hashimoto's disease, they are very interesting for pregnant women given that supplementation significantly decreases the percentage of postpartum thyroiditis and definitive hypothyroidism. In Graves' disease, selenium supplementation results in euthyroidism being achieved more rapidly and appears to have a beneficial effect on mild inflammatory orbitopathy. A risk of diabetes has been reported following long-term selenium supplementation, but few data are available on the side effects associated with such supplementation and further studies are required.

Oxidative stress in graves' disease

Increased reactive oxygen species (ROS) generation and the consequent oxidative damage are involved in the development of several diseases, including autoimmune diseases. Graves' disease is an autoimmune disorder characterized by hyperthyroidism and, less frequently, orbitopathy. Hyperthyroidism is characterized by increased oxidative stress. Untreated hyperthyroidism is associated with an increase of several parameters of oxidative stress and in most studies (but not all) by an increase of antioxidant defense enzymes. Restoration of euthyroidism with antithyroid drug is associated with a reversal of the biochemical abnormalities associated with oxidative stress. Animal and human studies suggest that increased ROS may directly contribute to some clinical manifestation of the disease, including orbitopathy. Antioxidants administered alone improve some clinical signs and symptoms of hyperthyroidism and, when associated with antithyroid drugs, induce a more rapid control of clinical manifestations and a faster achievement of euthyroidism. A large randomized clinical trial has shown that antioxidant supplementation (selenium) may also be beneficial for mild Graves' orbitopathy.

N-acetylcysteine reduces markers of differentiation in 3T3-L1 adipocytes

Oxidative stress plays a critical role in the pathogenesis of diabetes, hypertension and atherosclerosis. Some authors reported that fat accumulation correlates to systemic oxidative stress in humans and mice, but the relationship of lipid production and oxidative metabolism is still unclear. In our laboratory we used 3T3-L1 preadipocytes, which are able to differentiate into mature adipocytes and accumulate lipids, as obesity model. We showed that intracellular reactive oxygen species (ROS) and antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities increased in parallel with fat accumulation. Meanwhile N-acetylcysteine (NAC), a well known antioxidant and Glutathione (GSH) precursor, inhibited ROS levels as well as fat accumulation in a concentration-dependent manner. NAC also inhibited both adipogenic transcription factors CCAAT/enhancer binding protein beta (C/EBP β) and peroxisomal proliferator activated receptor gamma (PPAR γ) expression; we suggested that intracellular GSH content could be responsible for these effects.

Selenium and thyroid autoimmunity

The trace element selenium (Se) occurs in the form of the amino acid selenocysteine in selenoproteins. Selenoproteins exerts multiple physiological effects in human health, many of which are related with regulation of reduction-oxidation processes. In fact, the selenoenzyme families of glutathione peroxidase (GPx) and thioredoxin reductase (TRx) display the ability to act as antioxidants, protecting cells from oxidative damage. Furthermore, another class of selenoproteins are the iodothyronine deiodinase enzymes (DIO), which catalyze the conversion of thyroxine (T4) in triiodothyronine (T3), then exerting a fine tuned control on thyroid hormones metabolism. Several studies have investigated the potential positive effects of Se supplementation in thyroid diseases, characterized by increased levels of hydrogen peroxide and free radicals, like autoimmune chronic thyroiditis. These studies have supplied evidences indicating that Se supplementation, maximizing the antioxidant enzymes activity, may reduce the thyroid inflammatory status. Then, it may be postulated that Se could play a therapeutical role in thyroid autoimmune diseases. Despite the fact that recent studies seem to be concordant about Se beneficial effects in decreasing thyroid peroxidase antibodies (TPOAb) titers and ameliorating the ultrasound echogenicity pattern, several doubts have to be still clarified, before advising Se supplementation in chronic autoimmune thyroiditis.

Thyroid hormone effect in human hepatocytes

We have already demonstrated that a combined treatment of methimazole and an antioxidant mixture improved the condition of hyperthyroid patients both biochemically and clinically. Elevated thyroid hormone levels might trigger signs and symptoms of hyperthyroidism through the increase of free radicals. To study the direct effect of thyroid hormone on cellular markers of oxidative stress, we carried out in vitro assays in which 0.1-20.0 nM T3 (6.5-1300.0 ng/dl) doses were added to culture media of the human hepatocyte cell line Hep G2 for 1-24 h. T3 increased malondialdehyde (MDA) and intracellular oxidized glutathione (GSSG) levels; SOD activity was also higher with hormone treatment, whereas catalase and glutathione peroxidase activities showed no variation at different T3 doses and during all experimental times. When ascorbic acid was added to the culture, the MDA level decreased and SOD activity was increased. With higher doses of T3 (e.g. 200 nM), cell death occurred (69% of apoptotic cells). The increase in SOD activity was not enough to overcome the effect of T3 since MDA and GSSG remained high during a 24-h experiment. We showed a beneficial effect of ascorbic acid when cells were exposed to a T3 dose of 20 nM, a higher level of hormone than that achieved in hyperthyroidism.

Oxidative stress in patients with Graves' ophthalmopathy: relationship between oxidative DNA damage and clinical evolution

PURPOSE

To evaluate the relationship between oxidative stress and clinical evolution in patients with Graves' ophthalmopathy (GO).

METHODS

Thirty-one euthyroid GO patients and 25 healthy subjects participated in this study. Oxidative DNA damage was assessed by determination of the 8-hydroxy-2'-deoxyguanosine (8-OHdG) level in urine by ELISA. The relationship of oxidative DNA damage to the clinical evolutions of GO, especially the smoking status, clinical activity scores (CAS), and ophthalmopathy index was examined.

RESULTS

The mean 8-OHdG was significantly higher in GO patients than that of normal controls (12.6+/-5.7 vs 6.7+/-2.5 ng/mg creatinine, P<0.001). Smokers had significant higher 8-OHdG than did never smokers in GO patients (P=0.029), but not in healthy controls (P=0.374). Among GO patients, only CAS remained significantly correlated with 8-OHdG (P=0.001) after adjusting for age, sex, disease duration, the status of antithyroid drug and smoking, and thyroid-stimulating hormone level. Patients with active GO (CAS>3) had higher 8-OHdG than did the patients with CAS <or=3 (16.3+/-4.9 vs 8.6+/-3.0 ng/mg creatinine).

CONCLUSIONS

Our findings suggest that urinary 8-OHdG is increased in GO patients and is correlated with the disease activity. Smoking had a higher impact on the increased 8-OHdG among GO patients.

Methimazole protects lungs during hepatic ischemia-reperfusion injury in rats: an effect not induced by hypothyroidism

BACKGROUND

Hepatic ischemia-reperfusion injury may lead to remote organ failure with mortal respiratory dysfunction. The aim of the present study was to analyze the possible protective effects of methimazole on lungs after hepatic ischemia-reperfusion injury.

METHODS

Forty male Wistar albino rats were randomized into five groups: a control group, in which bilateral pulmonary lobectomy was done; a hepatic ischemia-reperfusion group, in which bilateral pulmonary lobectomy was done after hepatic ischemia-reperfusion; a thyroidectomy-ischemia-reperfusion group (total thyroidectomy followed by, 7 days later, bilateral pulmonary lobectomy after hepatic ischemia-reperfusion); a methimazole-ischemia-reperfusion group (following methimazole administration for 7 days, bilateral pulmonary lobectomy was done after hepatic ischemia-reperfusion); and a methimazole +L-thyroxine-ischemia-reperfusion group (following methimazole and L-thyroxine administration for 7 days, bilateral pulmonary lobectomy was performed after hepatic ischemia-reperfusion). Pulmonary tissue specimens were evaluated histopathologically and for myeloperoxidase and malondialdehyde levels.

RESULTS

All of the ischemia-reperfusion intervention groups had higher pulmonary injury scoring indices than the control group (P < 0.001). Pulmonary injury index of the ischemia-reperfusion group was higher than that of both the methimazole-supplemented hypothyroid and euthyroid groups (P = 0028; P = 0,038, respectively) and was similar to that of the thyroidectomized group. Pulmonary tissue myeloperoxidase and malondialdehyde levels in the ischemia-reperfusion group were similar with that in the thyroidectomized rats but were significantly higher than that in the control, and both the methimazole-supplemented hypothyroid and euthyroid groups.

CONCLUSION

Methimazole exerts a protective role on lungs during hepatic ischemia-reperfusion injury, which can be attributed to its anti-inflammatory and anti-oxidant effects rather than hypothyroidism alone.

Determination of oxidative stress in thyroid tissue and plasma of patients with Graves' disease

BACKGROUND

The aim of our study was to evaluate the oxidant/antioxidant status of thyroid tissue in Graves' disease (GD) patients and to compare the results of GD thyroid tissue with plasma of patients and healthy controls.

METHODS

We studied 25 consecutive patients with GD hyperthyroidism who underwent surgical treatment. The patients were divided into groups according to the duration of antithyroid drug treatment, the type of antithyroid drugs used, the presence of ophthalmopathy, and recurrence after a complete course of antithyroid drugs. Thiobarbituric acid-reacting substances (TBARS), glutathione peroxidase (GPx) activity, superoxide dismutase (SOD) activity, and total thiol (t-SH) content of tissue and plasma samples were determined.

RESULTS

TBARS concentrations were found to be significantly increased in GD patients' plasma compared with controls' plasma (0.1+/-0.02 nmol/mg protein vs. 0.062+/-0.01 nmol/mg protein). Significantly decreased t-SH concentrations were measured in GD patients' plasma compared with controls (8.26+/-1.9 nmol/mg protein vs. 13.03+/-3.3 nmol/mg protein). Tissue TBARS, t-SH, GPx, and SOD measurements in GD patients indicated significantly increased concentrations compared with the plasma levels of patients. Patients with shorter treatment duration before the operation had significantly increased plasma and tissue TBARS and decreased plasma and tissue t-SH concentrations. Patients on propylthiouracil treatment had significantly lower plasma and tissue concentrations of TBARS than patients on methimazole. Patients with recurrence had significantly higher plasma and tissue TBARS and lower plasma and tissue t-SH concentrations than patients treated for the first time.

CONCLUSIONS

In euthyroid GD patients on antithyroid drugs, increased oxidative stress and a compensatory increase in the antioxidant defense system are more prominent in thyroid tissue than in plasma. Patients who relapsed had markers indicating increased oxidative stress. Thus, ongoing autoimmunity may contribute to increased oxidative stress in GD patients, even in the euthyroid state.