Original article 143
The association between Helicobacter pylori infection, type 1 diabetes mellitus, and autoimmune thyroiditis Osama A. Zekrya and Hassan A. Abd Elwahidb Departments of aPediatrics and bFamily Medicine, Faculty of Medicine, Suez Canal University, Ismailia, Egypt Correspondence to Hassan A. Abd Elwahid, MD, Department of Family Medicine, Faculty of Medicine, Suez Canal University, Ismailia, Postal code 41511, Egypt Tel: + 20 109 315 9111; fax: + 20 643 232 523; e-mail: [email protected]
Received 21 June 2013 Accepted 10 October 2013 Journal of the Egyptian Public Health Association 2013, 88:143–147
Background Type 1 diabetes mellitus (T1DM) can be associated with an increased prevalence of Helicobacter pylori infection, which could contribute to the pathogenesis of autoimmune thyroiditis observed in this disease. Aim The aim of this study was to assess the relationship between H. pylori infection and T1DM and to identify of the interconnection between H. pylori infection and autoimmune thyroiditis in patients with T1DM. Methods A case–control design was used. The study group included 60 children and adolescents with T1DM who were selected from the pediatric outpatient clinic of Suez Canal University Hospital by a systematic random sampling method. The control group included 60 healthy children and adolescents matched for age and sex and selected from among relatives (brothers or cousins) of the patients with T1DM. The study participants were subjected to several investigations including estimation of levels of HbA1c, thyroid stimulating hormone (TSH), T3, T4, anti-thyroglobulin (anti-Tg), and anti-thyroid peroxidase (anti-TPO). Results The mean age of the patients with T1DM was 12.53 ± 2.35 years, whereas that of the control group was 12.30 ± 1.98 years, with no statistically significant difference between the two groups. The patients with diabetes had significantly higher levels of H. pylori IgG, TSH, anti-TPO, and anti-Tg (20.43 ± 14.84 m/ml, 4.03 ± 1.53 mIu/l, 14.98 ± 5.04 Iu/ml, and 5.66 ± 3.37 Iu/ml, respectively) and significantly lower levels of T3 and T4 (120 ± 15.86 mg/dl and 4.93 ± 0.93 mg/dl, respectively) compared with the control group. In addition, the seroprevalence rate of H. pylori, anti-Tg, and anti-TPO was significantly higher in diabetic patients, and the duration of diabetes was significantly longer in H. pylori-positive patients with higher levels of HbA1c, insulin requirement, TSH, anti-TPO, and anti-Tg. Conclusion and recommendations The association between H. pylori infection and autoimmune thyroiditis in patients with T1DM was revealed in this study. Hence, screening and treatment of H. pylori infection in T1DM patients is recommended. Keywords: autoimmune thyroiditis, Helicobacter pylori, type 1 diabetes mellitus
J Egypt Public Health Assoc 88:143–147 & 2013 Egyptian Public Health Association 0013-2446
Introduction Helicobacter pylori was first cultivated from human gastric mucosa in 1983 and since then it has emerged as one of the most common chronic bacterial infections worldwide. Its prevalence ranges from 40 to 80% in the general population of developed and developing countries [1]. The relationship between diabetes mellitus and H. pylori infection is controversial. Some studies found a high prevalence of H. pylori infection in patients with either type I diabetes mellitus (T1DM) or type II diabetes mellitus [2]. The effect of H. pylori on diabetes mellitus could be explained by the presence of elevated levels of inflammatory cytokines, which could lead to 0013-2446 & 2013 Egyptian Public Health Association
phosphorylation of serine residues on the insulin receptor substrate, preventing its interaction with insulin receptors and finally inhibiting insulin action. H. pylori infections can also lead to hyperglycemia in patients with diabetes mellitus; the mechanisms are thought to be by the secretion of counter-regulatory hormones because of stress, as well as by the production of cytokines. Cytokines by themselves can stimulate the secretion of insulin counter-regulatory hormones, and they can also directly influence carbohydrate metabolism [3]. In contrast, other studies showed that H. pylori infection is not associated with diabetes mellitus, as there is no difference in the prevalence of H. pylori infection between individuals with and those DOI: 10.1097/01.EPX.0000437621.23560.de
Copyright © Egyptian Public Health Association. Unauthorized reproduction of this article is prohibited.
144
Journal of the Egyptian Public Health Association
without diabetes, regardless of the type and duration of diabetes [4,5]. The incidence of autoimmune diseases, mainly autoimmune thyroiditis, is increased in patients with T1DM. Up to 20% of patients with T1DM are positive for antithyroid, anti-thyroglobulin (anti-Tg), and anti-thyroid peroxidase (anti-TPO) antibodies, and 2–5% of them develop autoimmune hypothyroidism [6]. Infection by H. pylori induces acute polymorphonuclear infiltration in the gastric mucosa. If the infection is not effectively cleared, this acute cellular infiltrate is gradually replaced by an immunologically mediated, chronic, predominantly mononuclear cellular infiltrate [7]. The latter is characterized by local production and systemic diffusion of proinflammatory cytokines, which may influence remote tissue and organ systems. As a result, H. pylori infection has been epidemiologically linked to some extradigestive conditions, including endocrine disorders [8]. This is based on the detection of monoclonal antibodies against cytotoxin-associated gene A + H. pylori strains, which cross-react with follicular cells of the thyroid gland, and also on the fact that H. pylori strains possessing the cytotoxin-associated gene A pathogenicity island carrying a gene encoding endogenous peroxidase. Moreover, the strong correlation between anti-H. pylori IgG antibodies and thyroid autoantibodies, and the observation that eradication of H. pylori infection is followed by a gradual decrease in the levels of thyroid autoantibodies, suggest that H. pylori antigens might be involved in the pathogenesis of autoimmune atrophic thyroiditis [9]. As a result of this controversy on the relationship between H. pylori infection, diabetes mellitus, and autoimmune thyroiditis, we tried to assess the relationship between H. pylori infection and T1DM as the primary objective of this study. The secondary objective was to determine the interconnection between H. pylori infection and autoimmune thyroiditis in patients with T1DM.
background and were matched as possible for age and sex. Written consent was obtained from the parents of all participants. Diagnosis of T1DM was based on the criteria of the American Diabetes Association [11]. The data obtained from patients with T1DM included age, sex, anthropometric measurements (weight and height), duration of diabetes, and daily insulin units per kilogram of body weight (IU/kg/day). Patients with clinical hypothyroidism or hyperthyroidism and patients on H. pylori eradication therapy, steroids, or immunosuppressive therapy were excluded. Venous blood samples were collected from the study groups (patients and control) and subjected to the following assays: (1) Measurement of HbA1c levels by chromatography on Cobas 600 (Roche, Mannheim, Germany). (2) Assessment of thyroid stimulating hormone (TSH), T3, and T4 levels by electrochemiluminescence immunoassay on Cobas E 411(Roche). (3) Assessment of the levels of thyroid antibodies, antiTg and anti-TPO, by an immunoenzymatic assay. Anti-Tg was considered positive if the titer was higher than 4 IU/ml, and anti-TPO was considered positive if the titer was higher than 20 IU/ml. (4) Assessment of the H. pylori IgG antibody titer in the serum using an enzyme-linked immunosorbent assay kit (Monobind Inc., USA); a level greater than 20 U/ml was considered to be strongly positive.
Ethical consideration
Field work was conducted after obtaining approval from the Ethics and Research Committee, Faculty of Medicine, Suez Canal University. The following ethical points were taken into consideration on the basis of the Declaration of Helsinki [12]: (i) confidentiality; (ii) the activities of the research did not lead the patients and physicians to commit acts that diminish their self-respect; (iii) approval by the research committee.
Patients and methods This case–control study was conducted at the Suez Canal University Hospital in Ismailia, Egypt. A sample of 60 children and adolescents with T1DM was selected from the study population with an estimated prevalence of anti-TPO of 16.9% (from a previous study) [6], a 95% confidence coefficient, and a 10% confidence interval [10]. The expected nonresponse rate of the participants was taken in consideration during sample size calculation. The T1DM group included 60 children and adolescents who were recruited from the pediatric outpatient clinic of Suez Canal University Hospital during the period from December 2012 to April 2013 by a systematic random sampling method, in which every third person with T1DM was included in the study. The control group included 60 healthy children who were selected from among relatives (brothers or cousins) of the patients with T1DM; they had a similar socioeconomic
Statistical analysis
All statistical analyses were carried out using the SPSS software package – version-16 (SPSS Inc., Chicago, Illinois, USA). Descriptive statistics and measures of central tendency and dispersion, as well as appropriate significance tests, were applied according to the type of variable. Student’s t-test, group t-test, was used to detect the significance of differences between the groups as regards continuous variables. The w2-test was used to assess the significance of differences between groups as regards categorical variables, with odds ratio estimation to determine the risk ratio with 95% confidence interval. Pearson’s bivariate correlation analysis was used to study the significance of linear association between the antiH. pylori IgG titer and other biochemical variables in patients with T1DM. A P-value of less than 0.05 was considered to be the significance cutoff point.
Copyright © Egyptian Public Health Association. Unauthorized reproduction of this article is prohibited.
H. pylori, T1DM, and autoimmune thyroiditis Zekry and Abd Elwahid 145
Results The study included 120 children and adolescents who were allocated into 2 groups (60/group). Their age ranged from 8–17 with a mean of 12.4 ± 2.2 years. The total number of males was 56 (46.7%) and that of females was 64 (53.3%). However there were no significant difference between T1DM and control groups regarding age as illustrated in Table 1. The distribution of sex among the two groups was equal (not presented in Table 1). Differences between baseline biochemical characteristics of the two groups were compared using the group t-test. The T1DM group had significantly higher levels of H. pylori IgG, TSH, anti-TPO, and anti-Tg. In contrast, T3 and T4 levels were significantly lower in the T1DM group in comparison with the control group, but they were in the normal range (Table 1). The study group was classified according to H. pylori status into two groups: H. pylori positive (serum antiH. pylori IgG antibodies >20 U/ml) and H. pylori negative (anti-H. pylori IgG antibodies r20 U/ml). Anti-Tg was consideredpositive if the antibody titer was higher than 4 IU/ml, and anti-TPO was considered positive if the antibody titer was higher than 20 IU/ml. The different categories were cross tabulated with conduction of w2, odds ratio (OR) and 95% CI of OR. Table 2 shows that the seroprevalence rate of H. pylori was significantly higher in patients with T1DM than in healthy controls (40 vs. 16.7%, P = 0.008, OR = 2.4). The T1DM group was 2.4-fold more likely to be positive for H. pylori IgG compared with the control group. In addition, thyroid autoimmunity was significantly higher in patients with T1DM than in healthy controls. Anti-TPO was positive in 16.7% (10/60) of patients with T1DM and 3.3% (2/60) of controls (P = 0.015). Anti-Tg was positive in 43.3%
(26/60) of patients and 6.7% (4/60) of controls (Po0.001). T1DM patients were five times more liable to have anti-TPO autoimmunity and 6.5 times more prone to Tg autoimmunity compared with controls. Patients with T1DM were divided into two groups on the basis of seroprevalance of H. pylori: H. pylori positive and H. pylori negative. There were no significant differences between the two groups as regards the age of the children and the T3 and T4 titers. The duration of diabetes was significantly longer in H. pylori-positive T1DM patients; they also had significantly higher levels of HbA1c, insulin dosage per day, TSH, anti-TPO, and anti-Tg autoantibodies in comparison with the H. pylori-negative T1DM patients (Table 3). Pearson’s bivariate correlation analysis was used to study the significance of linear associations between the antiH. pylori IgG titer and other biochemical variables in patients with T1DM. The results showed that the antiH pylori IgG titer was insignificantly correlated with diabetes duration (r = 0.224, P = 0.292) and TSH (r = 0.274, P = 0.195), T3 (r = 0.312, P = 0.137); T4 (r = 0. 223, P = 0.295), and anti-Tg autoantibody titers (r = 0.362, P = 0.082). In contrast, the antiH. pylori IgG titer was significantly correlated with the anti-TPO titer (r = 0.476, P = 0.019; Fig. 1), insulin requirement (r = 0.676, P = 0.0001; Fig. 2), and the HbA1c titer (r = 0.865, P = 0.0001).
Discussion The present case-control study revealed a significant difference in the level of H. pylori IgG between children with T1DM and normal children. The mean level
Table 1. Baseline characteristics of the study group Mean SD Patients (n = 60)
Control group (n = 60)
t-valuea
P
12.53 ± 2.35 20.43 ± 14.84 4.03 ± 1.53 120 ± 15.86 4.93 ± 0.93 14.98 ± 5.04 5.66 ± 3.37
12.30 ± 1.98 11.93 ± 6.31 3.00 ± 1.19 132 ± 15.27 5.90 ± 1.20 12.12 ± 3.64 2.86 ± 1.17
0.587 4.081 4.127 – 4.221 4.911 3.568 6.072
0.558 0.0001 0.0001 0.0001 0.0001 0.001 0.0001
Age in years H. pylori IgG (U/ml) TSH (mIU/l) T3 (mg/dl) T4 (mg/dl) Anti-TPO (IU/ml) Anti-Tg (IU/ml)
H. pylori, Helicobacter pylori; Tg, thyroglobulin; TPO, thyroid peroxidase; TSH, thyroid stimulating hormone. a Degree of freedom = 118.
Table 2. Seroprevalence rates of anti-Helicobacter pylori and anti-thyroid antibodies among the study group Nondiabetic patients (n = 60) [N (%)]
w2
P
OR
95% CI of OR
24 (40.0) 36 (60.0)
10 (16.7) 50 (83.3)
8.04
0.008
2.40
1.25–4.58
10 (16.7) 50 (83.3)
2 (3.3) 58 (96.7)
5.93
0.015
5.00
1.14–21.86
26 (43.3) 34 (56.7)
4 (6.7) 56 (93.3)
21.51
0.0001
6.50
2.42–17.49
Diabetic patients (n = 60) [N (%)] H. pylori IgG Positive Negative TPO autoimmunity Positive Negative Tg autoimmunity Positive Negative
CI, confidence interval; H. pylori, Helicobacter pylori; OR, odds ratio; Tg, thyroglobulin; TPO, thyroid peroxidase.
Copyright © Egyptian Public Health Association. Unauthorized reproduction of this article is prohibited.
146
Journal of the Egyptian Public Health Association
Table 3. Comparison between Helicobacter pylori-positive and Helicobacter pylori-negative T1DM patients with regard to biochemical data
Age in years Insulin (IU/kg/day) Duration of diabetes (years) HbA1c (%) TSH (mIU/l) T3 (mg/dl) T4 (mg/dl) Anti-TPO (IU/ml) Anti-Tg (IU/ml)
H. pylori positive (n = 24)
H. pylori negative (n = 36)
t-valuea
P
12.00 ± 2.40 1.20 ± 0.22 9.25 ± 2.73 7.75 ± 1.67 5.16 ± 1.49 125 ± 14.14 6.25 ± 1.39 18.58 ± 5.59 8.81 ± 2.67
12.89 ± 2.29 0.80 ± 0.15 6.11 ± 1.78 5.72 ± 1.20 3.27 ± 1.00 116.9 ± 16.31 5.67 ± 1.01 12.58 ± 2.75 3.56 ± 1.76
1.446 8.257 5.382 5.448 5.868 1.974 1.879 5.532 9.207
0.154 0.0001 0.0001 0.0001 0.0001 0.053 0.065 0.0001 0.0001
H. pylori, Helicobacter pylori; Tg, thyroglobulin; TPO, thyroid peroxidase; TSH, thyroid stimulating hormone. a Degrees of freedom = 58.
Figure 1.
Relationship between Helicobacter pylori IgG and anti-thyroid peroxidase (TPO) titers in the H. pylori-positive diabetic patients (n, 24; r, 0.476; and P, 0.01).
Figure 2.
Correlation between levels of Helicobacter pylori IgG and insulin requirements among H. pylori-positive diabetic patients (n, 24; r, 0.676; and P, 0.0001).
of H. pylori IgG in children with T1DM was more than 20 U/ml, which is the cutoff level for H. pylori IgG positivity. However it was below 20 U/ml in normal children. It should be mentioned that the presence of
anti-H. pylori IgG antibodies is suggestive of previous exposure or active infection. A positive serologic result cannot distinguish current from previous infection and cannot be used to assess response to therapy. Moreover, the seroprevalence rate of H. pylori IgG was 2.4 times higher in the children with T1DM than in the control group. The insulin requirements and duration of diabetes were also significantly higher in children with T1DM infected with H. pylori than in noninfected children with T1DM. In addition, there was a significant positive linear association between anti-H pylori IgG titers and HbA1c levels. However, the increased insulin requirement in patients with T1DM is dependent on the elevation in HbA1c levels. These results highlight the interaction between diabetes mellitus and H. pylori infection. On the basis of the literature, this association may be explained by the role of H. pylori infection in the induction of chronic inflammation and production of cytokines, leading to impaired secretion of insulin, increased anti-insulin activity, and altered carbohydrate metabolism. All these effects translate into decreased glycemic control and increased insulin requirement [3]. The results of the present study are in accordance with the results of other studies that reported an increased prevalence of H. pylori infection in diabetic patients [13,14]. The effect of H. pylori infection on glycemic control in T1DM patients was also elucidated in another study by Gasbarrini et al. [15]. Another conclusion could be drawn from our result on the effect of diabetes mellitus on the increased incidence of H. pylori infection – that is, H. pylori is a result rather than a cause of DM. This effect can be explained by reduced gastric motility and peristaltic activity in diabetic patients, which may promote H. pylori colonization. In addition, various chemical changes in gastric mucosa following nonenzymatic glycosylation of mucins or increased sialic acid were observed in diabetic patients. These changes may promote adhesion of H. pylori to gastric mucosa cells [16]. Our results also revealed a statistically significantly higher level of TSH and thyroid antibodies (anti-TG and antiTPO) and lower T3 and T4 levels in the T1DM group compared with the control group. Patients with diabetes were also more prone to have an increased seroprevalence rate of anti-TPO and anti-Tg antibodies compared with the
Copyright © Egyptian Public Health Association. Unauthorized reproduction of this article is prohibited.
H. pylori, T1DM, and autoimmune thyroiditis Zekry and Abd Elwahid 147
control group. Moreover, H. pylori-infected diabetic patients were more liable to have statistically higher TSH, anti-TG, and anti-TPO levels compared with noninfected patients with diabetes. These results show the greater vulnerability of diabetic patients to autoimmune thyroiditis and subclinical hypothyroidism. It could also be concluded that there is an association between H. pylori infection in diabetic patients and the development of autoimmune thyroiditis. This conclusion is augmented by the finding of significant positive linear associations between anti-H pylori IgG titers and anti-TPO levels. The pathogenesis of autoimmune thyroiditis includes both genetic and environmental factors. Some bacteria and viruses are suspected of being able to mimic the antigenic profile on the thyroid cell membrane and play an important role in the onset of autoimmune diseases [17]. One of the most important bacterial strains involved in the pathogenesis of autoimmune thyroiditis is the cytotoxin-associated gene-A-positive H. pylori strain, which shows some nucleotide sequences similar to the thyroid peroxidase sequence [18]. Other studies have demonstrated a positive linear regression between H. pylori antibody titers and microsomal autoantibodies, with a significant reduction in these antibodies after H. pylori eradication [19,20]. Crossreactivity of antibodies produced against thyroid antigens during H. pylori infections could potentially induce the production of autoantibodies against H + K + -ATPase in the gastric mucosa, similar to that seen on H. pylori infection [21]. The interconnection between H. pylori infection and autoimmune thyroiditis was also elucidated in a study by Larizza et al. [22]. They found a significant interaction between HLADRB1*0301, a well-known marker of autoimmunity, and H. pylori infection in patients with autoimmune thyroiditis. This allele has been specifically involved in both cellular and humoral reactions against self-structures such as thyroid cells. The conclusion of the present study was derived from the observed relationship between H. pylori infection, T1DM, and autoimmune thyroiditis. Hence, screening for H. pylori infection in children with T1DM is advisable because of its greater impact on this disease, in addition to its influence on the development of autoimmune thyroiditis, especially when dealing with preventable and treatable infection. Further studies incorporating a larger group of patients and exploring the relationship between H. pylori infection, T1DM, and autoimmune thyroiditis in more detail are recommended. These studies should also answer a new research question on the extent of reduction in the incidence of autoimmune thyroiditis that could be achieved by eradication of H. pylori in patients with T1DM. Limitations of the study
This is a case–control study. In addition, the study group was selected from an urban community, limiting the generalizability of the results. The research question of the present study can be better answered by using a
prospective design to reach conclusions as regards causal links with a higher level of evidence.
Acknowledgements The authors acknowledge the laboratory physicians and technicians for their help and support in conducting the lab work. The cooperation of the nursing staff in data collection is highly appreciated.
Conflicts of interest There are no conflicts of interest.
References 1 Genta RM. The immunobiology of Helicobacter pylori gastritis. Semin Gastrointest Dis 1997; 8:2–11. 2 Arslan D, Kendirci M, Kurtoglu S, Kula M. Helicobacter pylori infection in children with insulin dependent diabetes mellitus. J Pediatr Endocrinol Metab 2000; 13:553–556. 3 McMahon MM, Bistrian BR. Host defenses and susceptibility to infection in patients with diabetes mellitus. Infect Dis Clin North Am 1995; 9:1–9. 4 Anastasios R, Goritsas C, Papamihail C, Trigidou R, Garzonis P, Ferti A. Helicobacter pylori infection in diabetic patients: prevalence and endoscopic findings. Eur J Intern Med 2002; 13:376–379. 5 Stanciu OG, Trifan A, Sfarti C, Cojocariu C, Stanciu C. Rev Med Chir Soc Med Nat Iasi. Rev Med 2003; 107:59–65. 6 Kordonouri O, Klinghammer A, Lang EB, Gru¨ters-Kieslich A, Grabert M, Holl RW. Thyroid autoimmunity in children and adolescents with type 1 diabetes: a multicenter survey. Diabetes Care 2002; 25:1346–1350. 7 Graham DY, Osato MS, Olson CA, Zhang J, Figura N. Effect of H. pylori infection and CagA status on leukocyte counts and liver function tests: extragastric manifestations of H. pylori infection. Helicobacter 1998; 3:174–178. 8 Perri F. Serum tumour necrosis factor-alpha is increased in patients with Helicobacter pylori infection and CagA antibodies. Ital J Gastroenterol Hepatol 1999; 31:290–294. 9 Triantafillidis JK, Georgakopoulos D, Gikas A, Merikas E, Peros G, Sofroniadou K, et al. Relation between Helicobacter pylori infection, thyroid hormone levels and cardiovascular risk factors on blood donors. Hepatogastroenterology 2003; 50 (Suppl 2): cccxviii–cccxx. 10 WHO. Virtual resource center of the public health initiative: biostatics and epidemiology. Available at: http://203.90.70.117/phi/1.Epidemiology.asp. [Accessed 10 March 2012]. 11 Gavin JR, Alberti KGMM, Davidson MB, DeFronzo RA, Drash A, Gabbe SG, et al. Report of the expert committee on the diagnosis and classification of diabetes mellitus. Diabetes Care 2003; 26 (Suppl 1): S5–S20. 12 Carlson RV, Boyd KM, Webb DJ. The revision of the Declaration of Helsinki: past, present and future. Br J Clin Pharmacol 2004; 57:695–713. 13 De Luis DA, De La Calle H, Roy G, Martin De Argila C, Valdezate S, Canton R, Boixeda D. Helicobacter pylori infection and insulin-dependent diabetes mellitus. Diabetes Res Clin Pract 1998; 39:143–146. 14 Jafarzadeh A, Rezayati MT, Nemati M. Specific serum immunoglobulin G to H. pylori and CagA in healthy children and adults (south-east of Iran). World J Gastroenterol 2007; 13:3117–3121. 15 Gasbarrini A, Ojetti V, Pitocco D, De Luca A, Franceschi F, Candelli M, et al. Helicobacter pylori infection in patients affected by insulin-dependent diabetes mellitus. Eur J Gastroenterol Hepatol 1998; 10:469–472. 16 Senturk O, Canturk Z, C ¸ etinarslan B, Ercin C, Hulagu S, Canturk NZ. Prevalence and comparisons of five different diagnostic methods for Helicobacter pylori in diabetic patients. Endocr Res 2001; 27 (1–2): 179–189. 17 Rapoport B, McLachlan SM. Thyroid autoimmunity. J Clin Invest 2001; 108:1253–1259. 18 Tomb J-F, White O, Kerlavage AR, Clayton RA, Sutton GG, Fleischmann RD, et al. The complete genome sequence of the gastric pathogen Helicobacter pylori. Nature 1997; 388:539–547. 19 Atherton JC. H. pylori virulence factors. Br Med Bull 1998; 54:105–120. 20 Bertalot G, Montresor G, Tampieri M, Spasiano A, Pedroni M, Milanesi B, et al. Decrease in thyroid autoantibodies after eradication of Helicobacter pylori infection. Clin Endocrinol (Oxf) 2004; 61:650–652. 21 D’Elios MM, Bergman MP. Cytotoxic T cells in H. pylori-related gastric autoimmunity and gastric lymphoma. J Biomed Biotechnol 2010; 2010: 104918. 22 Larizza D, Calcaterra V, Martinetti M, Negrini R, De Silvestri A, Cisternino M, et al. Helicobacter pylori infection and autoimmune thyroid disease in young patients: the disadvantage of carrying the human leukocyte antigenDRB1*0301 allele. J Clin Endocrinol Metab 2006; 91:176–179.
Copyright © Egyptian Public Health Association. Unauthorized reproduction of this article is prohibited.
The association between Helicobacter pylori infection, type 1 diabetes mellitus, and autoimmune thyroiditis Osama A. Zekrya and Hassan A. Abd Elwahidb Departments of aPediatrics and bFamily Medicine, Faculty of Medicine, Suez Canal University, Ismailia, Egypt Correspondence to Hassan A. Abd Elwahid, MD, Department of Family Medicine, Faculty of Medicine, Suez Canal University, Ismailia, Postal code 41511, Egypt Tel: + 20 109 315 9111; fax: + 20 643 232 523; e-mail: [email protected]
Received 21 June 2013 Accepted 10 October 2013 Journal of the Egyptian Public Health Association 2013, 88:143–147
Background Type 1 diabetes mellitus (T1DM) can be associated with an increased prevalence of Helicobacter pylori infection, which could contribute to the pathogenesis of autoimmune thyroiditis observed in this disease. Aim The aim of this study was to assess the relationship between H. pylori infection and T1DM and to identify of the interconnection between H. pylori infection and autoimmune thyroiditis in patients with T1DM. Methods A case–control design was used. The study group included 60 children and adolescents with T1DM who were selected from the pediatric outpatient clinic of Suez Canal University Hospital by a systematic random sampling method. The control group included 60 healthy children and adolescents matched for age and sex and selected from among relatives (brothers or cousins) of the patients with T1DM. The study participants were subjected to several investigations including estimation of levels of HbA1c, thyroid stimulating hormone (TSH), T3, T4, anti-thyroglobulin (anti-Tg), and anti-thyroid peroxidase (anti-TPO). Results The mean age of the patients with T1DM was 12.53 ± 2.35 years, whereas that of the control group was 12.30 ± 1.98 years, with no statistically significant difference between the two groups. The patients with diabetes had significantly higher levels of H. pylori IgG, TSH, anti-TPO, and anti-Tg (20.43 ± 14.84 m/ml, 4.03 ± 1.53 mIu/l, 14.98 ± 5.04 Iu/ml, and 5.66 ± 3.37 Iu/ml, respectively) and significantly lower levels of T3 and T4 (120 ± 15.86 mg/dl and 4.93 ± 0.93 mg/dl, respectively) compared with the control group. In addition, the seroprevalence rate of H. pylori, anti-Tg, and anti-TPO was significantly higher in diabetic patients, and the duration of diabetes was significantly longer in H. pylori-positive patients with higher levels of HbA1c, insulin requirement, TSH, anti-TPO, and anti-Tg. Conclusion and recommendations The association between H. pylori infection and autoimmune thyroiditis in patients with T1DM was revealed in this study. Hence, screening and treatment of H. pylori infection in T1DM patients is recommended. Keywords: autoimmune thyroiditis, Helicobacter pylori, type 1 diabetes mellitus
J Egypt Public Health Assoc 88:143–147 & 2013 Egyptian Public Health Association 0013-2446
Introduction Helicobacter pylori was first cultivated from human gastric mucosa in 1983 and since then it has emerged as one of the most common chronic bacterial infections worldwide. Its prevalence ranges from 40 to 80% in the general population of developed and developing countries [1]. The relationship between diabetes mellitus and H. pylori infection is controversial. Some studies found a high prevalence of H. pylori infection in patients with either type I diabetes mellitus (T1DM) or type II diabetes mellitus [2]. The effect of H. pylori on diabetes mellitus could be explained by the presence of elevated levels of inflammatory cytokines, which could lead to 0013-2446 & 2013 Egyptian Public Health Association
phosphorylation of serine residues on the insulin receptor substrate, preventing its interaction with insulin receptors and finally inhibiting insulin action. H. pylori infections can also lead to hyperglycemia in patients with diabetes mellitus; the mechanisms are thought to be by the secretion of counter-regulatory hormones because of stress, as well as by the production of cytokines. Cytokines by themselves can stimulate the secretion of insulin counter-regulatory hormones, and they can also directly influence carbohydrate metabolism [3]. In contrast, other studies showed that H. pylori infection is not associated with diabetes mellitus, as there is no difference in the prevalence of H. pylori infection between individuals with and those DOI: 10.1097/01.EPX.0000437621.23560.de
Copyright © Egyptian Public Health Association. Unauthorized reproduction of this article is prohibited.
144
Journal of the Egyptian Public Health Association
without diabetes, regardless of the type and duration of diabetes [4,5]. The incidence of autoimmune diseases, mainly autoimmune thyroiditis, is increased in patients with T1DM. Up to 20% of patients with T1DM are positive for antithyroid, anti-thyroglobulin (anti-Tg), and anti-thyroid peroxidase (anti-TPO) antibodies, and 2–5% of them develop autoimmune hypothyroidism [6]. Infection by H. pylori induces acute polymorphonuclear infiltration in the gastric mucosa. If the infection is not effectively cleared, this acute cellular infiltrate is gradually replaced by an immunologically mediated, chronic, predominantly mononuclear cellular infiltrate [7]. The latter is characterized by local production and systemic diffusion of proinflammatory cytokines, which may influence remote tissue and organ systems. As a result, H. pylori infection has been epidemiologically linked to some extradigestive conditions, including endocrine disorders [8]. This is based on the detection of monoclonal antibodies against cytotoxin-associated gene A + H. pylori strains, which cross-react with follicular cells of the thyroid gland, and also on the fact that H. pylori strains possessing the cytotoxin-associated gene A pathogenicity island carrying a gene encoding endogenous peroxidase. Moreover, the strong correlation between anti-H. pylori IgG antibodies and thyroid autoantibodies, and the observation that eradication of H. pylori infection is followed by a gradual decrease in the levels of thyroid autoantibodies, suggest that H. pylori antigens might be involved in the pathogenesis of autoimmune atrophic thyroiditis [9]. As a result of this controversy on the relationship between H. pylori infection, diabetes mellitus, and autoimmune thyroiditis, we tried to assess the relationship between H. pylori infection and T1DM as the primary objective of this study. The secondary objective was to determine the interconnection between H. pylori infection and autoimmune thyroiditis in patients with T1DM.
background and were matched as possible for age and sex. Written consent was obtained from the parents of all participants. Diagnosis of T1DM was based on the criteria of the American Diabetes Association [11]. The data obtained from patients with T1DM included age, sex, anthropometric measurements (weight and height), duration of diabetes, and daily insulin units per kilogram of body weight (IU/kg/day). Patients with clinical hypothyroidism or hyperthyroidism and patients on H. pylori eradication therapy, steroids, or immunosuppressive therapy were excluded. Venous blood samples were collected from the study groups (patients and control) and subjected to the following assays: (1) Measurement of HbA1c levels by chromatography on Cobas 600 (Roche, Mannheim, Germany). (2) Assessment of thyroid stimulating hormone (TSH), T3, and T4 levels by electrochemiluminescence immunoassay on Cobas E 411(Roche). (3) Assessment of the levels of thyroid antibodies, antiTg and anti-TPO, by an immunoenzymatic assay. Anti-Tg was considered positive if the titer was higher than 4 IU/ml, and anti-TPO was considered positive if the titer was higher than 20 IU/ml. (4) Assessment of the H. pylori IgG antibody titer in the serum using an enzyme-linked immunosorbent assay kit (Monobind Inc., USA); a level greater than 20 U/ml was considered to be strongly positive.
Ethical consideration
Field work was conducted after obtaining approval from the Ethics and Research Committee, Faculty of Medicine, Suez Canal University. The following ethical points were taken into consideration on the basis of the Declaration of Helsinki [12]: (i) confidentiality; (ii) the activities of the research did not lead the patients and physicians to commit acts that diminish their self-respect; (iii) approval by the research committee.
Patients and methods This case–control study was conducted at the Suez Canal University Hospital in Ismailia, Egypt. A sample of 60 children and adolescents with T1DM was selected from the study population with an estimated prevalence of anti-TPO of 16.9% (from a previous study) [6], a 95% confidence coefficient, and a 10% confidence interval [10]. The expected nonresponse rate of the participants was taken in consideration during sample size calculation. The T1DM group included 60 children and adolescents who were recruited from the pediatric outpatient clinic of Suez Canal University Hospital during the period from December 2012 to April 2013 by a systematic random sampling method, in which every third person with T1DM was included in the study. The control group included 60 healthy children who were selected from among relatives (brothers or cousins) of the patients with T1DM; they had a similar socioeconomic
Statistical analysis
All statistical analyses were carried out using the SPSS software package – version-16 (SPSS Inc., Chicago, Illinois, USA). Descriptive statistics and measures of central tendency and dispersion, as well as appropriate significance tests, were applied according to the type of variable. Student’s t-test, group t-test, was used to detect the significance of differences between the groups as regards continuous variables. The w2-test was used to assess the significance of differences between groups as regards categorical variables, with odds ratio estimation to determine the risk ratio with 95% confidence interval. Pearson’s bivariate correlation analysis was used to study the significance of linear association between the antiH. pylori IgG titer and other biochemical variables in patients with T1DM. A P-value of less than 0.05 was considered to be the significance cutoff point.
Copyright © Egyptian Public Health Association. Unauthorized reproduction of this article is prohibited.
H. pylori, T1DM, and autoimmune thyroiditis Zekry and Abd Elwahid 145
Results The study included 120 children and adolescents who were allocated into 2 groups (60/group). Their age ranged from 8–17 with a mean of 12.4 ± 2.2 years. The total number of males was 56 (46.7%) and that of females was 64 (53.3%). However there were no significant difference between T1DM and control groups regarding age as illustrated in Table 1. The distribution of sex among the two groups was equal (not presented in Table 1). Differences between baseline biochemical characteristics of the two groups were compared using the group t-test. The T1DM group had significantly higher levels of H. pylori IgG, TSH, anti-TPO, and anti-Tg. In contrast, T3 and T4 levels were significantly lower in the T1DM group in comparison with the control group, but they were in the normal range (Table 1). The study group was classified according to H. pylori status into two groups: H. pylori positive (serum antiH. pylori IgG antibodies >20 U/ml) and H. pylori negative (anti-H. pylori IgG antibodies r20 U/ml). Anti-Tg was consideredpositive if the antibody titer was higher than 4 IU/ml, and anti-TPO was considered positive if the antibody titer was higher than 20 IU/ml. The different categories were cross tabulated with conduction of w2, odds ratio (OR) and 95% CI of OR. Table 2 shows that the seroprevalence rate of H. pylori was significantly higher in patients with T1DM than in healthy controls (40 vs. 16.7%, P = 0.008, OR = 2.4). The T1DM group was 2.4-fold more likely to be positive for H. pylori IgG compared with the control group. In addition, thyroid autoimmunity was significantly higher in patients with T1DM than in healthy controls. Anti-TPO was positive in 16.7% (10/60) of patients with T1DM and 3.3% (2/60) of controls (P = 0.015). Anti-Tg was positive in 43.3%
(26/60) of patients and 6.7% (4/60) of controls (Po0.001). T1DM patients were five times more liable to have anti-TPO autoimmunity and 6.5 times more prone to Tg autoimmunity compared with controls. Patients with T1DM were divided into two groups on the basis of seroprevalance of H. pylori: H. pylori positive and H. pylori negative. There were no significant differences between the two groups as regards the age of the children and the T3 and T4 titers. The duration of diabetes was significantly longer in H. pylori-positive T1DM patients; they also had significantly higher levels of HbA1c, insulin dosage per day, TSH, anti-TPO, and anti-Tg autoantibodies in comparison with the H. pylori-negative T1DM patients (Table 3). Pearson’s bivariate correlation analysis was used to study the significance of linear associations between the antiH. pylori IgG titer and other biochemical variables in patients with T1DM. The results showed that the antiH pylori IgG titer was insignificantly correlated with diabetes duration (r = 0.224, P = 0.292) and TSH (r = 0.274, P = 0.195), T3 (r = 0.312, P = 0.137); T4 (r = 0. 223, P = 0.295), and anti-Tg autoantibody titers (r = 0.362, P = 0.082). In contrast, the antiH. pylori IgG titer was significantly correlated with the anti-TPO titer (r = 0.476, P = 0.019; Fig. 1), insulin requirement (r = 0.676, P = 0.0001; Fig. 2), and the HbA1c titer (r = 0.865, P = 0.0001).
Discussion The present case-control study revealed a significant difference in the level of H. pylori IgG between children with T1DM and normal children. The mean level
Table 1. Baseline characteristics of the study group Mean SD Patients (n = 60)
Control group (n = 60)
t-valuea
P
12.53 ± 2.35 20.43 ± 14.84 4.03 ± 1.53 120 ± 15.86 4.93 ± 0.93 14.98 ± 5.04 5.66 ± 3.37
12.30 ± 1.98 11.93 ± 6.31 3.00 ± 1.19 132 ± 15.27 5.90 ± 1.20 12.12 ± 3.64 2.86 ± 1.17
0.587 4.081 4.127 – 4.221 4.911 3.568 6.072
0.558 0.0001 0.0001 0.0001 0.0001 0.001 0.0001
Age in years H. pylori IgG (U/ml) TSH (mIU/l) T3 (mg/dl) T4 (mg/dl) Anti-TPO (IU/ml) Anti-Tg (IU/ml)
H. pylori, Helicobacter pylori; Tg, thyroglobulin; TPO, thyroid peroxidase; TSH, thyroid stimulating hormone. a Degree of freedom = 118.
Table 2. Seroprevalence rates of anti-Helicobacter pylori and anti-thyroid antibodies among the study group Nondiabetic patients (n = 60) [N (%)]
w2
P
OR
95% CI of OR
24 (40.0) 36 (60.0)
10 (16.7) 50 (83.3)
8.04
0.008
2.40
1.25–4.58
10 (16.7) 50 (83.3)
2 (3.3) 58 (96.7)
5.93
0.015
5.00
1.14–21.86
26 (43.3) 34 (56.7)
4 (6.7) 56 (93.3)
21.51
0.0001
6.50
2.42–17.49
Diabetic patients (n = 60) [N (%)] H. pylori IgG Positive Negative TPO autoimmunity Positive Negative Tg autoimmunity Positive Negative
CI, confidence interval; H. pylori, Helicobacter pylori; OR, odds ratio; Tg, thyroglobulin; TPO, thyroid peroxidase.
Copyright © Egyptian Public Health Association. Unauthorized reproduction of this article is prohibited.
146
Journal of the Egyptian Public Health Association
Table 3. Comparison between Helicobacter pylori-positive and Helicobacter pylori-negative T1DM patients with regard to biochemical data
Age in years Insulin (IU/kg/day) Duration of diabetes (years) HbA1c (%) TSH (mIU/l) T3 (mg/dl) T4 (mg/dl) Anti-TPO (IU/ml) Anti-Tg (IU/ml)
H. pylori positive (n = 24)
H. pylori negative (n = 36)
t-valuea
P
12.00 ± 2.40 1.20 ± 0.22 9.25 ± 2.73 7.75 ± 1.67 5.16 ± 1.49 125 ± 14.14 6.25 ± 1.39 18.58 ± 5.59 8.81 ± 2.67
12.89 ± 2.29 0.80 ± 0.15 6.11 ± 1.78 5.72 ± 1.20 3.27 ± 1.00 116.9 ± 16.31 5.67 ± 1.01 12.58 ± 2.75 3.56 ± 1.76
1.446 8.257 5.382 5.448 5.868 1.974 1.879 5.532 9.207
0.154 0.0001 0.0001 0.0001 0.0001 0.053 0.065 0.0001 0.0001
H. pylori, Helicobacter pylori; Tg, thyroglobulin; TPO, thyroid peroxidase; TSH, thyroid stimulating hormone. a Degrees of freedom = 58.
Figure 1.
Relationship between Helicobacter pylori IgG and anti-thyroid peroxidase (TPO) titers in the H. pylori-positive diabetic patients (n, 24; r, 0.476; and P, 0.01).
Figure 2.
Correlation between levels of Helicobacter pylori IgG and insulin requirements among H. pylori-positive diabetic patients (n, 24; r, 0.676; and P, 0.0001).
of H. pylori IgG in children with T1DM was more than 20 U/ml, which is the cutoff level for H. pylori IgG positivity. However it was below 20 U/ml in normal children. It should be mentioned that the presence of
anti-H. pylori IgG antibodies is suggestive of previous exposure or active infection. A positive serologic result cannot distinguish current from previous infection and cannot be used to assess response to therapy. Moreover, the seroprevalence rate of H. pylori IgG was 2.4 times higher in the children with T1DM than in the control group. The insulin requirements and duration of diabetes were also significantly higher in children with T1DM infected with H. pylori than in noninfected children with T1DM. In addition, there was a significant positive linear association between anti-H pylori IgG titers and HbA1c levels. However, the increased insulin requirement in patients with T1DM is dependent on the elevation in HbA1c levels. These results highlight the interaction between diabetes mellitus and H. pylori infection. On the basis of the literature, this association may be explained by the role of H. pylori infection in the induction of chronic inflammation and production of cytokines, leading to impaired secretion of insulin, increased anti-insulin activity, and altered carbohydrate metabolism. All these effects translate into decreased glycemic control and increased insulin requirement [3]. The results of the present study are in accordance with the results of other studies that reported an increased prevalence of H. pylori infection in diabetic patients [13,14]. The effect of H. pylori infection on glycemic control in T1DM patients was also elucidated in another study by Gasbarrini et al. [15]. Another conclusion could be drawn from our result on the effect of diabetes mellitus on the increased incidence of H. pylori infection – that is, H. pylori is a result rather than a cause of DM. This effect can be explained by reduced gastric motility and peristaltic activity in diabetic patients, which may promote H. pylori colonization. In addition, various chemical changes in gastric mucosa following nonenzymatic glycosylation of mucins or increased sialic acid were observed in diabetic patients. These changes may promote adhesion of H. pylori to gastric mucosa cells [16]. Our results also revealed a statistically significantly higher level of TSH and thyroid antibodies (anti-TG and antiTPO) and lower T3 and T4 levels in the T1DM group compared with the control group. Patients with diabetes were also more prone to have an increased seroprevalence rate of anti-TPO and anti-Tg antibodies compared with the
Copyright © Egyptian Public Health Association. Unauthorized reproduction of this article is prohibited.
H. pylori, T1DM, and autoimmune thyroiditis Zekry and Abd Elwahid 147
control group. Moreover, H. pylori-infected diabetic patients were more liable to have statistically higher TSH, anti-TG, and anti-TPO levels compared with noninfected patients with diabetes. These results show the greater vulnerability of diabetic patients to autoimmune thyroiditis and subclinical hypothyroidism. It could also be concluded that there is an association between H. pylori infection in diabetic patients and the development of autoimmune thyroiditis. This conclusion is augmented by the finding of significant positive linear associations between anti-H pylori IgG titers and anti-TPO levels. The pathogenesis of autoimmune thyroiditis includes both genetic and environmental factors. Some bacteria and viruses are suspected of being able to mimic the antigenic profile on the thyroid cell membrane and play an important role in the onset of autoimmune diseases [17]. One of the most important bacterial strains involved in the pathogenesis of autoimmune thyroiditis is the cytotoxin-associated gene-A-positive H. pylori strain, which shows some nucleotide sequences similar to the thyroid peroxidase sequence [18]. Other studies have demonstrated a positive linear regression between H. pylori antibody titers and microsomal autoantibodies, with a significant reduction in these antibodies after H. pylori eradication [19,20]. Crossreactivity of antibodies produced against thyroid antigens during H. pylori infections could potentially induce the production of autoantibodies against H + K + -ATPase in the gastric mucosa, similar to that seen on H. pylori infection [21]. The interconnection between H. pylori infection and autoimmune thyroiditis was also elucidated in a study by Larizza et al. [22]. They found a significant interaction between HLADRB1*0301, a well-known marker of autoimmunity, and H. pylori infection in patients with autoimmune thyroiditis. This allele has been specifically involved in both cellular and humoral reactions against self-structures such as thyroid cells. The conclusion of the present study was derived from the observed relationship between H. pylori infection, T1DM, and autoimmune thyroiditis. Hence, screening for H. pylori infection in children with T1DM is advisable because of its greater impact on this disease, in addition to its influence on the development of autoimmune thyroiditis, especially when dealing with preventable and treatable infection. Further studies incorporating a larger group of patients and exploring the relationship between H. pylori infection, T1DM, and autoimmune thyroiditis in more detail are recommended. These studies should also answer a new research question on the extent of reduction in the incidence of autoimmune thyroiditis that could be achieved by eradication of H. pylori in patients with T1DM. Limitations of the study
This is a case–control study. In addition, the study group was selected from an urban community, limiting the generalizability of the results. The research question of the present study can be better answered by using a
prospective design to reach conclusions as regards causal links with a higher level of evidence.
Acknowledgements The authors acknowledge the laboratory physicians and technicians for their help and support in conducting the lab work. The cooperation of the nursing staff in data collection is highly appreciated.
Conflicts of interest There are no conflicts of interest.
References 1 Genta RM. The immunobiology of Helicobacter pylori gastritis. Semin Gastrointest Dis 1997; 8:2–11. 2 Arslan D, Kendirci M, Kurtoglu S, Kula M. Helicobacter pylori infection in children with insulin dependent diabetes mellitus. J Pediatr Endocrinol Metab 2000; 13:553–556. 3 McMahon MM, Bistrian BR. Host defenses and susceptibility to infection in patients with diabetes mellitus. Infect Dis Clin North Am 1995; 9:1–9. 4 Anastasios R, Goritsas C, Papamihail C, Trigidou R, Garzonis P, Ferti A. Helicobacter pylori infection in diabetic patients: prevalence and endoscopic findings. Eur J Intern Med 2002; 13:376–379. 5 Stanciu OG, Trifan A, Sfarti C, Cojocariu C, Stanciu C. Rev Med Chir Soc Med Nat Iasi. Rev Med 2003; 107:59–65. 6 Kordonouri O, Klinghammer A, Lang EB, Gru¨ters-Kieslich A, Grabert M, Holl RW. Thyroid autoimmunity in children and adolescents with type 1 diabetes: a multicenter survey. Diabetes Care 2002; 25:1346–1350. 7 Graham DY, Osato MS, Olson CA, Zhang J, Figura N. Effect of H. pylori infection and CagA status on leukocyte counts and liver function tests: extragastric manifestations of H. pylori infection. Helicobacter 1998; 3:174–178. 8 Perri F. Serum tumour necrosis factor-alpha is increased in patients with Helicobacter pylori infection and CagA antibodies. Ital J Gastroenterol Hepatol 1999; 31:290–294. 9 Triantafillidis JK, Georgakopoulos D, Gikas A, Merikas E, Peros G, Sofroniadou K, et al. Relation between Helicobacter pylori infection, thyroid hormone levels and cardiovascular risk factors on blood donors. Hepatogastroenterology 2003; 50 (Suppl 2): cccxviii–cccxx. 10 WHO. Virtual resource center of the public health initiative: biostatics and epidemiology. Available at: http://203.90.70.117/phi/1.Epidemiology.asp. [Accessed 10 March 2012]. 11 Gavin JR, Alberti KGMM, Davidson MB, DeFronzo RA, Drash A, Gabbe SG, et al. Report of the expert committee on the diagnosis and classification of diabetes mellitus. Diabetes Care 2003; 26 (Suppl 1): S5–S20. 12 Carlson RV, Boyd KM, Webb DJ. The revision of the Declaration of Helsinki: past, present and future. Br J Clin Pharmacol 2004; 57:695–713. 13 De Luis DA, De La Calle H, Roy G, Martin De Argila C, Valdezate S, Canton R, Boixeda D. Helicobacter pylori infection and insulin-dependent diabetes mellitus. Diabetes Res Clin Pract 1998; 39:143–146. 14 Jafarzadeh A, Rezayati MT, Nemati M. Specific serum immunoglobulin G to H. pylori and CagA in healthy children and adults (south-east of Iran). World J Gastroenterol 2007; 13:3117–3121. 15 Gasbarrini A, Ojetti V, Pitocco D, De Luca A, Franceschi F, Candelli M, et al. Helicobacter pylori infection in patients affected by insulin-dependent diabetes mellitus. Eur J Gastroenterol Hepatol 1998; 10:469–472. 16 Senturk O, Canturk Z, C ¸ etinarslan B, Ercin C, Hulagu S, Canturk NZ. Prevalence and comparisons of five different diagnostic methods for Helicobacter pylori in diabetic patients. Endocr Res 2001; 27 (1–2): 179–189. 17 Rapoport B, McLachlan SM. Thyroid autoimmunity. J Clin Invest 2001; 108:1253–1259. 18 Tomb J-F, White O, Kerlavage AR, Clayton RA, Sutton GG, Fleischmann RD, et al. The complete genome sequence of the gastric pathogen Helicobacter pylori. Nature 1997; 388:539–547. 19 Atherton JC. H. pylori virulence factors. Br Med Bull 1998; 54:105–120. 20 Bertalot G, Montresor G, Tampieri M, Spasiano A, Pedroni M, Milanesi B, et al. Decrease in thyroid autoantibodies after eradication of Helicobacter pylori infection. Clin Endocrinol (Oxf) 2004; 61:650–652. 21 D’Elios MM, Bergman MP. Cytotoxic T cells in H. pylori-related gastric autoimmunity and gastric lymphoma. J Biomed Biotechnol 2010; 2010: 104918. 22 Larizza D, Calcaterra V, Martinetti M, Negrini R, De Silvestri A, Cisternino M, et al. Helicobacter pylori infection and autoimmune thyroid disease in young patients: the disadvantage of carrying the human leukocyte antigenDRB1*0301 allele. J Clin Endocrinol Metab 2006; 91:176–179.
Copyright © Egyptian Public Health Association. Unauthorized reproduction of this article is prohibited.
