Association Between Gut Microbiota and Autoimmune Thyroid Disease: A Systematic Review and Meta-Analysis.

Background: Autoimmune thyroid disease (AITD) is characterized by thyroid dysfunction and deficits in the autoimmune system. Growing attention has been paid toward the field of gut microbiota over the last few decades. Several recent studies have found that gut microbiota composition in patients with AITD has altered, but no studies have conducted systematic reviews on the association between gut microbiota and ATID. Methods: We searched PubMed, Web of Science, Embase, and Cochrane databases without language restrictions and conducted a systematic review and meta-analysis of eight studies, including 196 patients with AITD. Results: The meta-analysis showed that the alpha diversity and abundance of certain gut microbiota were changed in patients with AITD compared to the controls. Chao1,the index of the microflora richness, was increased in the Hashimoto's thyroiditis group compared to controls (SMD, 0.68, 95%CI: 0.16 to 1.20), while it was decreased in the Graves' disease group (SMD, -0.87, 95%CI: -1.46 to -0.28). In addition, we found that some beneficial bacteria like Bifidobacterium and Lactobacillus were decreased in the AITD group, and harmful microbiota like Bacteroides fragilis was significantly increased compared with the controls. Furthermore, the percentage of relevant abundance of other commensal bacteria such as Bacteroidetes, Bacteroides, and Lachnospiraceae was increased compared with the controls. Conclusions: This meta-analysis indicates an association between AITD and alteration of microbiota composition at the family, genus, and species levels. Systematic Review Registration: PROSPERO, identifier CRD42021251557.

Simulation Model for Hashimoto Autoimmune Thyroiditis Disease.

Hashimoto thyroiditis (HT) is a pathology that often causes a gradual thyroid insufficiency in affected patients due to the autoimmune destruction of this gland. The cellular immune response mediated by T helper lymphocytes TH1 and TH17 can induce the HT disease. In this pathologic condition, there is an imbalance between the TH17 and Treg lymphocytes as well as a gut microbiota dysfunction. The objective of this work was to describe the interactions of the cell subpopulations that participate in HT. To achieve this goal, we generated a mathematical model that allowed the simulation of different scenarios for the dynamic interaction between thyroid cells, the immune system, and the gut microbiota. We used a hypothetical-deductive design of mathematical modeling based on a system of ordinary differential equations, where the state variables are the TH1, TH17, and Treg lymphocytes, the thyrocytes, and the bacteria from gut microbiota. This work generated a compartmental model of the cellular immune response occurring in the thyroid gland. It was observed that TH1 and TH17 lymphocytes could increase the immune cells' activity, as well as activate effector cells directly and trigger the apoptosis and inflammation processes of healthy thyrocytes indirectly. Likewise, the model showed that a reduction in Treg lymphocytes could increase the activity of TH17 lymphocytes when an imbalance of the gut microbiota composition occurred. The numerical results highlight the TH1, TH17, and bacterial balance of the gut microbiota activities as important factors for the development of HT disease.

A rare case of cutaneous Papiliotrema (Cryptococcus) laurentii infection in a 23-year-old Caucasian woman affected by an autoimmune thyroid disorder with hypothyroidism.

In recent years, the frequency of infections due to saprophytic fungi has increased. Cryptococcus laurentii, recently classified as Papiliotrema laurentii, is responsible for fungemia, meningitis, and superficial infections. Here, we report the first case of cutaneous Papiliotrema (Cryptococcus) laurentii infection in a 23-year-old Caucasian woman affected by an autoimmune thyroiditis with hypothyroidism. Impairments of the immune system are often associated with unusual fungal infections, which cannot be neglected. The isolate strain was susceptible to Amphotericin B while resistant to fluconazole, itraconazole, voriconazole, and terbinafine. The patient was successfully treated with Amphotericin B.

The microbiota and autoimmunity: Their role in thyroid autoimmune diseases.

Since the 1970s, the role of infectious diseases in the pathogenesis of Graves' disease (GD) has been an object of intensive research. The last decade has witnessed many studies on Yersinia enterocolitica, Helicobacter pylori and other bacterial organisms and their potential impact on GD. Retrospective, prospective and molecular binding studies have been performed with contrary outcomes. Until now it is not clear whether bacterial infections can trigger autoimmune thyroid disease. Common risk factors for GD (gender, smoking, stress, and pregnancy) reveal profound changes in the bacterial communities of the gut compared to that of healthy controls but a pathogenetic link between GD and dysbiosis has not yet been fully elucidated. Conventional bacterial culture, in vitro models, next generation and high-throughput DNA sequencing are applicable methods to assess the impact of bacteria in disease onset and development. Further studies on the involvement of bacteria in GD are needed and may contribute to the understanding of pathogenetic processes. This review will examine available evidence on the subject.

Does microbiota composition affect thyroid homeostasis?

The intestinal microbiota is essential for the host to ensure digestive and immunologic homeostasis. When microbiota homeostasis is impaired and dysbiosis occurs, the malfunction of epithelial barrier leads to intestinal and systemic disorders, chiefly immunologic and metabolic. The role of the intestinal tract is crucial in the metabolism of nutrients, drugs, and hormones, including exogenous and endogenous iodothyronines as well as micronutrients involved in thyroid homeostasis. However, the link between thyroid homeostasis and microbiota composition is not yet completely ascertained. A pathogenetic link with dysbiosis has been described in different autoimmune disorders but not yet fully elucidated in autoimmune thyroid disease which represents the most frequent of them. Anyway, it has been suggested that intestinal dysbiosis may trigger autoimmune thyroiditis. Furthermore, hypo- and hyper-thyroidism, often of autoimmune origin, were respectively associated to small intestinal bacterial overgrowth and to changes in microbiota composition. Whether some steps of this thyroid network may be affected by intestinal microbiota composition is briefly discussed below.

[Helicobacter pylori infection: from gastric to systemic disease]. / Manifestazioni extragastriche dell'infezione da Helicobacter pylori.

H. pylori infection, through a chronic stimulation of the immune system and the occurrence of molecular mimicry mechanisms, is responsible for the majority of the gastroduodenal diseases and also for some extragastric disorders, including sideropenic anemia and idiopathic thrombocytopenic purpura; other diseases are under investigation.

Reactivity to Helicobacter pylori antigens in patients suffering from thyroid gland autoimmunity.

The role of infection in autoimmunity is widely discussed. In this study we concentrated on relationship between HELICOBACTER PYLORI as a very important gastroduodenal pathogen and autoimmune thyroiditis (AT). Forty seven AT patients and 34 healthy controls were enrolled. They were split into: THP ( H.PYLORI positive patients, n=17), THN ( H.PYLORI negative patients, n=30), CP ( H.PYLORI positive controls, n=17) and CN groups ( H.PYLORI negative controls, n=17). By protein microarray we analysed production of 23 cytokines and chemokines prior and post stimulation with H.PYLORI lysate and its lipopolysaccharide (LPS). Reactivity to lysate as well as to bacterial LPS differed within groups. The lowest basal cytokine and chemokine production was observed in CN group but these subjects reacted significantly to specific stimulation by increasing IFN-gamma (in comparison with THP p=0.01 for LPS and p=0.004 for H.PYLORI lysate) and TGF-beta production (p=0.015 for LPS). In contrast, IL-10 and IL-5 were decreased in this group. In CP, THN and THP groups, we observed in general higher chemokine response. THP group increased proinflammatory IL-6 after specific stimulation as well (in comparison with CP p<0.0001 for LPS stimulation). We observed different "reactivity pattern" to H.PYLORI within groups with low basal cytokine and chemokine production in healthy H.PYLORI negative controls but with clear specific response in IFN-gamma and TGF-beta production in this group. Adequate immune reaction which is joined to appropriate immunoregulation leads to prevention of the chronic infection and on the other hand may prevent the development of "connected" diseases such as autoimmune.

Infections and autoimmune thyroid diseases: parallel detection of antibodies against pathogens with proteomic technology.

Different types of infection are implicated in the pathogenesis of autoimmune thyroid diseases (AITD) through molecular mimicry or other mechanisms, but their role is disputed. Human studies support direct or indirect evidence of involvement of some viral and bacterial agents, but reports have provided conflicting and inconclusive results. Using a new automated multiplex array platform for the detection of antibodies, we determined seroreactivity against Toxoplasma gondii, Treponema pallidum, rubella virus, cytomegalovirus, and Epstein-Barr virus in a large group of Italian AITD patients and healthy controls. Only IgG concentrations against T. gondii were significantly higher in AITD patients than in controls, suggesting that these protozoa may be involved in the initiation of both Hashimoto's thyroiditis and Graves' disease.

Helicobacter pylori isolated from patients with tonsillar cancer or tonsillitis chronica could be of different genotype compared to isolates from gastrointestinal tract.

Helicobacter pylori from patients with different diseases, including so-called autoimmune thyroiditis, chronic tonsillitis and tonsillar cancer, was isolated and cultured. It was identified according to the genotype using labeled hybridization probes complementary to six sequences of cagA and vacA genes. Different types of strains were found in isolates from gastrointestinal tract and patients suffering from thyroiditis. Six out of seven genotyped isolates from patients in our Department of Otorhinolaryngology and Head and Neck Surgery exhibited the same genotype, differing from isolates obtained from other patients; the 7th isolate originated from a patient who had undergone surgery for deviatio septi nasi, at the same time suffering from autoimmune thyroiditis, having confirmed gastric infection by H. pylori from biopsy. This data made it possible to formulate the hypothesis on probable association of specific H. pylori genotype with chronic tonsillitis and tonsillar cancer. We assessed commercial transport media and improved nucleic acid isolation techniques and the RT-PCR-based tests, which allowed us to skip a culture step and to test directly the patients' samples; however, for full confirmation of our hypothesis and explanation of possible mechanisms of the contribution of Helicobacter sp. to the pathogenesis of the disease further data are to be collected and evaluated.

[Autoimmune thyroiditis--selected etiopathogenic mechanisms]. / Autoimunitní tyreoiditida--vybrané etiopatogenetické mechanizmy.

Autoimmune thyroiditis occurs as organ specific autoimmune disease not only as an isolated impairment of thyroid gland, but also linked to many autoimmune endocrinopathies. Genetic predisposition in the area of HLA antigens was followed up by patients with autoimmune thyroiditis diagnosed in this way and it appeared that genetic predisposition in isolated autoimmune thyroiditis is different when compared to the occurrence linked to endocrine polyglandular disease. In selected groups of patients with autoimmune disease also the influence of extraneous factors on the development of the autoimmune process was followed up, namely the influence of heavy metals and the influence of infectious agent--Helicobacter pylori. These factors have a different character of activation of autoimmune thyroiditis too, depending on the character of its manifestation as isolated disorder or in link to autoimmune polyglandular syndrome type II, or in link to the group of polyglandular activation of autoimmunity. To conclude, this study leads to the assumption, that autoimmune thyroiditis is a set of clinical syndromes that depends on the activation of the autoimmune process, rather than a strictly genetically and epigenetically characterized nosological unit.

Autoimmune thyroiditis and Helicobacter pylori--is there a connection?

OBJECTIVES: In this study we examined the anti-Helicobacter pylori (anti-H. pylori) antibodies in patients with autoimmune thyroiditis, with and without different polyglandular involvement, and in healthy controls. MATERIAL & METHODS: Patients with autoimmune thyroiditis (AT) were divided into three groups: Group A: 23 patients with isolated AT, Group B: 30 patients with AT as a part of polyglandular activation of autoimmunity, and Group C: 7 patients with AT as a part of autoimmune polyglandular syndrome type II. Thirty healthy individuals served as controls (Group D). Anti-H. pylori antibodies were determined first by ELISA for classes IgG, IgA, and IgM, and subsequently by immunoblot for classes IgG and IgA. RESULTS: ELISA: The number of patients with IgA antibodies in Group A (39%) and Group B (30%) differed significantly from controls (7%, p<0.05). Immunoblot: Anti-CagA antibodies were found in 13% of patients in Group A, 7% of Group B, 0% of Group C, and 20% of Group D. A higher seroprevalence, as compared to controls, was found for IgG to the VacA (p=0.01), 30 kDa (p=0.001), and 17 kDa (p=0.008) antigens in Group A and for IgG to the 30 kDa antigen in Group C (p=0.037). A significantly higher seroprevalence, as compared to controls, was likewise found for IgA to the 17 kDa antigen in Group A (p=0.015). CONCLUSIONS: A different distribution of antibodies to H. pylori antigens was found in patients with isolated AT compared to patients with AT coupled with a polyglandular syndrome.

Immunostimulatory probiotic Lactobacillus rhamnosus HN001 and Bifidobacterium lactis HN019 do not induce pathological inflammation in mouse model of experimental autoimmune thyroiditis.

The possibility that intestinal microflora contribute to the pathogenesis of autoimmune diseases has raised issues regarding the safety of probiotic organisms, especially those with immunostimulating properties, in individuals with such immune dysfunctions. In this study, the effect of consumption of probiotic lactic acid bacteria (LAB) strains Lactobacillus rhamnosus HN001(HN001) and Bifidobacterium lactis HN019 (HN019) on the induction and progression of experimental autoimmune thyroiditis (EAT) was investigated in CBA/CaH (H-2k) mice. HN001 or HN019 in skim milk were fed to mice daily (1-1.5 x 10(8) cfu/mouse/day) for 5 to 9 weeks. A mild form of EAT was induced by subcutaneous injection of mouse thyroglobulin (MTg) with either Freund's adjuvant (complete and incomplete, CFA and IFA) or lipopolysaccharide (LPS). The proliferative responses of spleen lymphocyte to MTg stimulation in vitro and the presence (and degree) of mononuclear cell infiltration in thyroid gland tissues were examined to assess the development and severity of EAT. The levels of serum anti-MTg antibodies (IgG1 and IgG2a) and spleen weight index were determined to detect the presence of autoimmune responses of mice receiving MTg. Results showed that 8 weeks after immunization, 16.67-50% of the mice developed mild EAT with lymphocyte infiltration in the thyroid glands. Probiotic feeding did not induce full-blown EAT. There were no differences in spleen weight index or the proliferative spleenocytes in response to PMA between mice that received MTg alone and mice that received MTg and probiotic LAB strains.

Increased prevalence of antibodies to enteropathogenic Yersinia enterocolitica virulence proteins in relatives of patients with autoimmune thyroid disease.

Infections have been implicated in the pathogenesis of a number of autoimmune diseases, and Yersinia enterocolitica (YE) might play a role in the development of autoimmune thyroid disease (AITD). Clinical evidence in support of this hypothesis has been inconclusive. We reasoned that looking earlier in the natural course of AITD might enhance chances of finding evidence for YE infection. Consequently, we determined seroreactivity against YE in subjects at risk of developing AITD, i.e. in 803 female relatives of AITD patients in self-proclaimed good health. As a comparison group we used 100 healthy women who participated in a program for reference values. IgG and IgA antibodies to virulence-associated outer membrane proteins (YOPs) of YE were measured by a specific assay. Serum thyroid peroxidase antibodies (TPO-Ab) as indicators of AITD were considered to be positive at levels of> 100 kU/l. The prevalence of YOP IgG-Ab was higher in AITD relatives than in controls (40.1% vs. 24%, P = 0.002), and the same was true for YOP IgA-Ab (22% vs. 13%, P < 0.05). Of the 803 AITD relatives, 44 had an increased or decreased plasma TSH, and 759 were euthyroid as evident from a normal TSH; the prevalence of YOP-Ab did not differ between these three subgroups. TPO-Ab were present in 10% of controls and in 27% of the AITD relatives (P < 0.001). The prevalence of TPO-Ab in the euthyroid AITD relatives was not different between YOP IgG-Ab positive and negative subjects (23.3% vs. 24.7%, NS), nor between YOP IgA-Ab positive and negative subjects (21.2% vs. 24.9%, NS). In conclusion, healthy female relatives of AITD patients have an increased prevalence of YOP antibodies, which, however, is not related to the higher prevalence of TPO antibodies in these subjects. The findings suggest a higher rate of persistent YE infection in AITD relatives. Susceptibility genes for AITD may also confer a risk for YE infection.

Extragastric mucosa-associated lymphoid tissue lymphoma showing the regression by Helicobacter pylori eradication therapy.

A 69-year-old man presented with right neck tumour. Primary thyroid MALT lymphoma occurring in Hasimoto's thyroiditis was diagnosed. He was also diagnosed to have gastric cancer with Helicobacter pylori infection. After subtotal gastrectomy by itself, thyroid lymphoma became smaller transiently. Then the patient was treated with H. pylori eradication therapy, resulting in the complete disappearance of lymphoma. Although H. pylori organisms were not detected in the lymphoma tissue by polymerase chain reaction (PCR), it might be implicated in the pathogenesis of extragastric MALT lymphomas.

[Autoimmune thyroiditis--an infectious disease?]. / Autoimmun thyroiditis--en infektionssygdom?

The aim was to review existing evidence of a possible role of infectious agents in the pathogenesis of autoimmune thyroid disease. Autoimmune thyroid disease is a polygenic, multifactorial disease in which genetically susceptible individuals are exposed to an environmental insult resulting in immune system activation. Different viruses (influenza B, rubella, retrovirus) have been associated with thyroiditis, but no single agent appears to be causative. There is no firm evidence of infection being an important trigger of autoimmune thyroid disease, and it has not been possible to isolate a microorganism neither by culture nor by molecular identification. Infection may be a precipitating factor in the development of autoimmune thyroid disease.

The infection by Helicobacter pylori strains expressing CagA is highly prevalent in women with autoimmune thyroid disorders.

UNLABELLED: H. pylori infection is putatively associated with extra-digestive disorders and may also play a role in the development of autoimmune thyroid diseases (ATD). It was recently found that monoclonal antibodies to an H. pylori strain with cagA-positivity reacted with follicular cells of the thyroid gland, and that an H. pylori organism possessing the cag pathogenicity island carried a gene encoding for an endogenous peroxidase. The aims of this study was (1); To ascertain whether the infection by strains endowed with an increased inflammatory potential (those expressing CagA) could further enhance the risk of developing ATD (2); To verify the possible existence of an immune cross-reactivity between autoantibodies to peroxidase and thyroglobulin and H. pylori antigens (3). To establish whether thyroid colloid antigens could cross-react with an anti-H. pylori serum. The study was partly designed retrospectively. We examined 41 consecutive women with ATD, and, as a control, 33 consecutive age- and socio-economic class-matched women without autoimmune thyroid disorders, living in the same area as patients, occurred at the same institution in the same period (six months). Both patients and controls were examined serologically for H. pylori infection and CagA status by Western blotting. Some serum samples were absorbed with H. pylori to determine whether the antibody levels decreased. Colloid proteins were resolved electrophoretically and matched with a hyperimmune serum raised in rabbits against a CagA-positive H. pylori. Thirty-two patients (78.0%) tested seropositive for H. pylori infection, vs. 16 controls (48.4%) (P = 0.008, OR = 3.78, RR = 1.61). The prevalence of anti-CagA antibodies was 71.8% in infected patients, and 50% in infected controls (P = 0.161, n.s.). The overall prevalence of infection by CagA-positive H. pylori was significantly higher in patients with ATD (23/41, or 56.0%) than that in controls (8/33, or 24.2%) (P = 0.006, OR = 3.99, RR = 2.31). The other tests gave negative or inexplicable results. IN CONCLUSION: CagA-positive H. pylori infection increases the risk of ATD development.

Helicobacter pylori infection is markedly increased in patients with autoimmune atrophic thyroiditis.

Infection by viral or bacterial pathogens has been suspected in playing a role in the development of autoimmune thyroid disease. Because Helicobacter pylori might be involved in the development of nongastrointestinal conditions such as rosacea, ischemic heart disease, and diabetes mellitus, we evaluated the prevalence of H. pylori infection in patients with autoimmune thyroid disease. Fifty-nine patients with autoimmune thyroid disease were included: autoimmune atrophic thyroiditis (n=21), Hashimoto's thyroiditis (n=18), and Graves' disease (n=20). Twenty patients with nontoxic multinodular goiter served as controls for nonautoimmune thyroid disease, and 11 patients with Addison's disease served as controls for nonthyroid endocrine autoimmune disease. The levels of anti-H. pylori immunoglobulin G (IgG) were determined, and a radiolabeled urea breath test were performed. The prevalence of H. pylori infection was markedly increased in the patients with autoimmune atrophic thyroiditis (85.7%), compared with the controls with nontoxic multinodular goiter (40%) and Addison's disease (45.4%). Infection by H. pylori resulted in increased levels of gastrin, pepsinogen I, and pepsinogen II in the H. pylori-positive groups, compared with the H. pylori-negative groups. A positive linear regression was found between the levels of microsomal autoantibodies and those of anti-H. pylori IgG in patients with autoimmune atrophic thyroiditis (n=21; r=0.79; p < 0.01). Finally, and although the overall prevalence of H. pylori infection was not increased, the anti-H. pylori IgG levels and the results from the breath test were higher in the patients with Graves' disease and Hashimoto's thyroiditis patients than in the controls. Clearly, the prevalence of H. pylori infection is increased in autoimmune atrophic thyroiditis and results in abnormalities of gastric secretory function. The strong relation between the levels of anti-H. pylori IgG and the levels of microsomal antibodies suggests that H. pylori antigens might be involved in the development of autoimmune atrophic thyroiditis or that autoimmune function in autoimmune atrophic thyroiditis may increase the likelihood of H. pylori infection.

Genetically determined target organ susceptibility in the pathogenesis of spontaneous autoimmune thyroiditis: aberrant expression of MHC-class II antigens and the possible role of virus.

Considerable controversy exists concerning the role of aberrant MHC-class II antigen expression in the pathogenesis of organ-specific auto-immune disease. Since Obese strain (OS) chickens are afflicted with a spontaneously occurring autoimmune thyroiditis (SAT), we have readdressed this pivotal question by investigating the chronical appearance of MHC-class II antigens on thyroid epithelial cells (TEC) of OS and normal healthy CB chickens before onset of overt clinical symptoms in the former. Among the candidates as potent inducers of aberrant MHC-class II antigen expression, interest in our studies focussed on the potential role of viruses in the development of SAT. Since aberrant MHC-class II antigen expression could prove to be an epiphenomenon of virally afflicted TEC, we determined 2,5-oligoadenylate synthetase and 2,5-oligoadenylatepolymer cytosol levels in both chicken lines. Our results indicate that the presence of infiltrating lymphocytes does not necessarily represent a prerequisite for the aberrant expression of MHC-class II antigens but coincides in most cases. However, the phenomenon seems to play a perpetuating rather than a causative role. Moreover, in support of a possible viral involvement, elevated levels of the 2,5-oligoadenylate synthetase and 2,5-oligomers could be demonstrated in TEC cytosol of OS chickens.