Role of genetic and non-genetic factors in the etiology of Graves' disease

Low regulatory T cell and high IL-17 mRNA expression in a mouse Graves' disease model

PURPOSE

Graves' disease (GD) is an autoimmune thyroid disease, and the most important characteristic of it is the presence of the thyroid-stimulating antibody (TSAb). The mechanisms of the TSAb elevation are still uncertain. Recent studies have suggested that the dysregulation of regulatory T cell (Treg) and T helper 17 (Th17) might stimulate the production of TSAb and be a pathogenesis of GD. However, the role of Treg and Th17 cells in the pathogenesis of GD is still debated. Our aim is to assess changes of Treg and Th17 cells in the spleen of a mouse in an in vivo GD model and try to explain the pathogenesis of GD.

METHODS

We used an adenovirus expressing the autoantigen thyroid-stimulating hormone receptor (Ad-TSHR289) to immunise mice in order to induce GD in the model. Flow cytometry was used to measure the frequencies of splenic Treg and Th17 cells and real-time PCR to analyse the mRNA expression of forkhead box P3(Foxp3) and interleukin-17(IL-17).

RESULTS

Compared with the Ad-Control group, the frequencies of CD4⁺CD25⁺Foxp3⁺ Treg cells were significantly decreased (p = 0.007) and gene expression of Foxp3 was down-regulated (p = 0.001) in the Ad-TSHR289 group. Though there was no significant difference in CD4⁺IL-17⁺ T cell subpopulation between the two groups (p = 0.336), the IL-17 mRNA expression was significantly up-regulated in the Ad-TSHR289 group (p = 0.001).

CONCLUSIONS

The pathogenesis of GD may be associated with reduced Treg cells and increased IL-17 gene expression. The increased IL-17 mRNA needs to be explained by other mechanisms but not Th17 cells.

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.

CD40 Signaling in Graves Disease Is Mediated Through Canonical and Noncanonical Thyroidal Nuclear Factor κB Activation

CD40, a tumor necrosis factor receptor, is a major immune-modulating susceptibility gene for Graves disease (GD) as well as for a variety of other autoimmune diseases. Its broad association with autoimmunity underscores its paramount role in the development of a normal adaptive immune response, primarily in coordinating effective antigen presentation. The molecular pathways by which CD40 activation in the thyroid induces GD are unknown. In this study, we investigated whether NF-κB, a ubiquitious family of transcription factors, mediates the downstream effects of thyroid-specific CD40 activation. Cultured primary human thyrocytes, from patients with and without GD, underwent CD40 stimulation. Once stimulated, cytokines and transcription factors specific for either the canonical nuclear factor κB (NF-κB)1 pathway [interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-α], which primarily recruits cells for innate immunity, or the noncanonical NF-κB2 pathway [B cell-activating factor of the TNF family, CC chemokine ligand (CCL)21], which directs B cell viability, were analyzed. Significant upregulation in the messenger RNA and protein levels of both canonical and noncanonical pathway cytokines was observed. Western blot analyses of the specific transcription factors for the NF-κB1 and NF-κB2 pathways (p65 and p100/p52, respectively) demonstrated that p65 is constitutively expressed. In contrast, CD40 stimulation robustly increased the expression of the NF-κB2 p52 transcription factor, and the upregulation was significantly more profound in the GD tissue than in the normal thyroid tissue. Our data show that CD40 activity in thyrocytes is prominently mediated via NF-κB and furthermore suggest that the NF-κB1 and NF-κB2 pathways both contribute to the triggering and the progression of GD.

Predictive Value of Gene Polymorphisms on Recurrence after the Withdrawal of Antithyroid Drugs in Patients with Graves' Disease

Graves' disease (GD) is one of the most common endocrine diseases. Antithyroid drugs (ATDs) treatment is frequently used as the first-choice therapy for GD patients in most countries due to the superiority in safety and tolerance. However, GD patients treated with ATD have a relatively high recurrence rate after drug withdrawal, which is a main limitation for ATD treatment. It is of great importance to identify some predictors of the higher recurrence risk for GD patients, which may facilitate an appropriate therapeutic approach for a given patient at the time of GD diagnosis. The genetic factor was widely believed to be an important pathogenesis for GD. Increasing studies were conducted to investigate the relationship between gene polymorphisms and the recurrence risk in GD patients. In this article, we updated the current literatures to highlight the predictive value of gene polymorphisms on recurrence risk in GD patients after ATD withdrawal. Some gene polymorphisms, such as CTLA4 rs231775, human leukocyte antigen polymorphisms (DRB1*03, DQA1*05, and DQB1*02) might be associated with the high recurrence risk in GD patients. Further prospective studies on patients of different ethnicities, especially studies with large sample sizes, and long-term follow-up, should be conducted to confirm the predictive roles of gene polymorphism.

Autoimmune Thyroid Diseases in Patients Treated with Alemtuzumab for Multiple Sclerosis: An Example of Selective Anti-TSH-Receptor Immune Response

Alemtuzumab, a humanized anti-CD52 monoclonal antibody, is approved for the treatment of active relapsing-remitting multiple sclerosis (MS). Alemtuzumab induces a rapid and prolonged depletion of lymphocytes from the circulation, which results in a profound immuno-suppression status followed by an immune reconstitution phase. Secondary to reconstitution autoimmune diseases represent the most common side effect of Alemtuzumab treatment. Among them, Graves' disease (GD) is the most frequent one with an estimated prevalence ranging from 16.7 to 41.0% of MS patients receiving Alemtuzumab. Thyrotropin (TSH) receptor (R)-reactive B cells are typically observed in GD and eventually present this autoantigen to T-cells, which, in turn, secrete several pro-inflammatory cytokines and chemokines. Given that reconstitution autoimmunity is more frequently characterized by autoantibody-mediated diseases rather than by destructive Th1-mediated disorders, it is not surprising that GD is the most commonly reported side effect of Alemtuzumab treatment in patients with MS. On the other hand, immune reconstitution GD was not observed in a large series of patients with rheumatoid arthritis treated with Alemtuzumab. This negative finding supports the view that patients with MS are intrinsically more at risk for developing Alemtuzumab-related thyroid dysfunctions and in particular of GD. From a clinical point of view, Alemtuzumab-induced GD is characterized by a surprisingly high rate of remission, both spontaneous and after antithyroid drugs, as well as by a spontaneous shift to hypothyroidism, which is supposed to result from a change from stimulating to blocking TSH-receptor antibodies. These immune and clinical peculiarities support the concept that antithyroid drugs should be the first-line treatment in Alemtuzumab-induced Graves' hyperthyroidism.

The phenotype of newly diagnosed Graves' disease in Italy in recent years is milder than in the past: results of a large observational longitudinal study

OBJECTIVE

The Merseburg triad (hyperthyroidism, goiter, and orbitopathy) characterizes classical description of Graves' disease (GD). Aim of this observational, longitudinal study was to evaluate the current clinical features of newly diagnosed GD in Italy.

MATERIALS AND METHODS

In two Northern Italy centers (Varese and Pavia), 283 consecutive patients (211 women, 72 men; mean age 47.4 years) with newly diagnosed GD were recruited in the years 2010-2014. Diagnosis was based on established criteria, and thyroid volume was assessed by ultrasonography. A clinical severity score (CSS) to assess the overall disease severity was developed by grading each component of the Merseburg triad.

RESULTS

At diagnosis, 45 % of patients had no goiter, and 30 % had a small goiter. The proportion of goitrous patients was much lower than in two Italian studies performed 20-30 years ago. Hyperthyroidism was subclinical in 16 % and mild in 29 % of patients, and Graves' orbitopathy was present in 20 %, usually mild, and active in only 2.5 % of patients. Using the CSS, less than half (44 %) of the patients had severe GD, while 22 % had mild and 34 % moderate disease. CSS was associated with a significantly higher risk of poorly controlled hyperthyroidism at 6 months.

CONCLUSIONS

In Italy, a relevant proportion of Graves' patients at diagnosis have mild to moderate GD; about half of them have no goiter, slightly less than one-fifth have subclinical hyperthyroidism, and only 20 % have GO. Thus, the clinical phenotype of GD is milder than in the past, possibly due to both earlier diagnosis and treatment, and improved iodine nutrition.

Controversies in the management of Graves' disease in children

Graves' disease (GD) is the most prevalent cause of thyrotoxicosis in children. Because spontaneous and lasting resolution of this condition occurs in only a minority of patients, most pediatric patients with GD will need radioactive iodine treatment (¹³¹I) or thyroidectomy. Whereas the medication propylthiouracil (PTU) had been used in the past, only methimazole (MMI) should be now used in children, as PTU is associated with an unacceptable risk of liver failure. However, MMI may be associated minor and major side effects, which may be minimized using lower doses. An area of controversy involves the optimal duration of antithyroid drug (ATD) therapy. For some children, the prolonged use of antithyroid drugs is a valid approach, but for most, this will not increase the chance of remission. When ¹³¹I is administered, dosages should be greater than 150 uCi/gm of thyroid tissue, with higher dosages needed for larger glands. Considering that there will be low-level whole body radiation exposure associated with ¹³¹I, this treatment is viewed as controversial by some and should be avoided in young children. When surgery is performed, near-total or total thyroidectomy is the recommended procedure. Complications for thyroidectomy in children are considerably higher than in adults. Thus, an experienced thyroid surgeon is needed when children have surgery. Overall, when different treatment options for GD are considered, the benefits, risks and viewpoints of the family need to be considered and discussed in full.

Management of hyperthyroidism due to Graves' disease: frequently asked questions and answers (if any)

Graves' disease is the most common cause of hyperthyroidism in iodine-replete areas. Although progress has been made in our understanding of the pathogenesis of the disease, no treatment targeting pathogenic mechanisms of the disease is presently available. Therapies for Graves' hyperthyroidism are largely imperfect because they are bound to either a high rate of relapsing hyperthyroidism (antithyroid drugs) or lifelong hypothyroidism (radioiodine treatment or thyroidectomy). Aim of the present article is to offer a practical guidance to the reader by providing evidence-based answers to frequently asked questions in clinical practice.

Hyperthyroidism

Hyperthyroidism is characterised by increased thyroid hormone synthesis and secretion from the thyroid gland, whereas thyrotoxicosis refers to the clinical syndrome of excess circulating thyroid hormones, irrespective of the source. The most common cause of hyperthyroidism is Graves' disease, followed by toxic nodular goitre. Other important causes of thyrotoxicosis include thyroiditis, iodine-induced and drug-induced thyroid dysfunction, and factitious ingestion of excess thyroid hormones. Treatment options for Graves' disease include antithyroid drugs, radioactive iodine therapy, and surgery, whereas antithyroid drugs are not generally used long term in toxic nodular goitre, because of the high relapse rate of thyrotoxicosis after discontinuation. β blockers are used in symptomatic thyrotoxicosis, and might be the only treatment needed for thyrotoxicosis not caused by excessive production and release of the thyroid hormones. Thyroid storm and hyperthyroidism in pregnancy and during the post-partum period are special circumstances that need careful assessment and treatment.

Concomitant Thyroid Disorders and Inflammatory Bowel Disease: A Literature Review

The aim of this report was to review and summarize the literature on cases of concomitant inflammatory bowel disease (IBD) and thyroid diseases. We included the following previous case reports of concomitant IBD and thyroid diseases: 16 cases of ulcerative colitis (UC) and Graves' disease (GD), 3 cases of Crohn's disease (CD) and GD, 10 cases of CD and Hashimoto's thyroiditis (HT), 4 cases of IBD and subacute thyroiditis (SAT) or SAT-like symptoms, and 13 cases of IBD (12/13 cases were CD) and amyloid goiter. There might be no obvious differences of prevalence of thyroid dysfunction (hyper- or hypothyroidism), GD, and thyroid cancer between IBD patients and general populations. However, concomitant UC and HT might be relatively common in patients with multiple autoimmune disorders, and AG is one of the complications with CD patients. There might be no obvious differences of fatal prognoses between IBD patients with thyroid diseases and patients with thyroid diseases without IBD.

Dissecting the Genetic Susceptibility to Graves' Disease in a Cohort of Patients of Italian Origin

Graves' disease (GD) is an autoimmune oligogenic disorder with a strong hereditary component. Several GD susceptibility genes have been identified and confirmed during the last two decades. However, there are very few studies that evaluated susceptibility genes for GD in specific geographic subsets. Previously, we mapped a new locus on chromosome 3q that was unique to GD families of Italian origin. In the present study, we used association analysis of single-nucleotide polymorphism (SNPs) at the 3q locus in a cohort of GD patients of Italian origin in order to prioritize the best candidates among the known genes in this locus to choose the one(s) best supported by the association. DNA samples were genotyped using the Illumina GoldenGate genotyping assay analyzing 690 SNP in the linked 3q locus covering all 124 linkage disequilibrium blocks in this locus. Candidate non-HLA (human-leukocyte-antigen) genes previously reported to be associated with GD and/or other autoimmune disorders were analyzed separately. Three SNPs in the 3q locus showed a nominal association (p < 0.05): rs13097181, rs763313, and rs6792646. Albeit these could not be further validated by multiple comparison correction, we were prioritizing candidate genes at a locus already known to harbor a GD-related gene, not hypothesis testing. Moreover, we found significant associations with the thyroid-stimulating hormone receptor (TSHR) gene, the cytotoxic T-lymphocyte antigen-4 (CTLA-4) gene, and the thyroglobulin (TG) gene. In conclusion, we identified three SNPs on chromosome 3q that may map a new GD susceptibility gene in this region which is unique to the Italian population. Furthermore, we confirmed that the TSHR, the CTLA-4, and the TG genes are associated with GD in Italians. Our findings highlight the influence of ethnicity and geographic variations on the genetic susceptibility to GD.

Serum prolidase levels in Graves' disease without ophthalmopathy and its association with oxidative status

OBJECTIVE

The aim of this study was to evaluate serum prolidase levels and its association with oxidative stress in autoimmune thyroid disease (AITD).

MATERIALS AND METHODS

25 with Hashimoto thyroiditis (HT) and 25 patients Graves' disease (GD), and 27 healthy controls were enrolled in the study. The patients with signs of Graves' ophthalmopathy were excluded from the study. Serum samples were obtained in euthyroid period at the third month of treatment. Serum prolidase, total antioxidant status (TAS), total oxidative stress (TOS), and total free sulfhydryl (-SH) levels were measured.

RESULTS

Serum prolidase levels were significantly higher in the patients with GD compared to the HT and the healthy control group. Oxidative stress index (OSI) and TOS levels of the patients with both GD and HT were significantly higher compared to those of the control group (p < 0.001, for each), while -SH levels were significantly lower (p < 0.001, for each). There was no significant difference between the patients with HT and healthy control group in terms of prolidase levels (p = 0.580). Prolidase levels were positively correlated with TOS and OSI and negatively correlated with -SH (r = 0.565, p = 0.003; r = 0.604, p = 0.001; r = -0.532, p = 0.006).

CONCLUSION

Serum prolidase activity is increased in GD patients without signs of ophthalmopathy, and showed a positive correlation with oxidative stress parameters.

Etiopathogenesis of Basedow's disease. Trends and current aspects

Basedow's disease (BD) owes its name to the German physician Karl Adolph von Basedow, who described in 1840 the clinical picture of exophthalmic toxic goitre. More than one century after the seminal paper of Karl von Basedow, the ultimate cause of BD remains to be fully elucidated. In the last years, evidence was accumulated indicating that BD is a polygenic and multifactorial disease that develops as a result of a complex interplay between genetic susceptibility and environmental and endogenous factors, which leads to the loss of immune tolerance to thyroid antigens and in particular to the TSH receptor. Our aim is to review the current knowledge on the pathogenesis of BD. To this purpose, we will firstly focus our attention on the role of genetic factors (the HLA complex, the genes encoding for thyroglobulin, the TSH receptor, CD40, CTLA-4 and PTPN22), and of environmental factors (iodine, infections, psychological stress, gender, smoking, thyroid damage, vitamin D, selenium, immune modulating agents) as possible causes of BD. Taking advantage of the experimental animal models of BD, we will then focus on the immunological mechanisms leading to the loss of tolerance in BD. The pathogenic role played by the chemokine system will be also reviewed.