Explore the impact of Streptococcal infection and immune Dysregulation on autoimmune Hashimoto’s disease development

Background: Hashimoto's thyroiditis (HT) is a widespread autoimmune disease that poses a significant public health concern worldwide. Objectives: The current study aims to investigate the effect of past-streptococcal infections, thyroid peroxidase (TPO) autoantibodies, and interleukin-10 (IL-10) levels on Hashimoto’s thyroiditis development. Methodology: A case–control study of 80 participants was conducted, including 30 healthy controls and 50 HT patients diagnosed by a specialist at the Endocrinology and Diabetic Center in Al-Sader Medical City. Blood samples were drawn from all participants to measure serum levels of TSH, T3, and T4 by a Cobas E114 Roche analyzer; TPO levels by electro-chemiluminescence immunoassay; anti-streptolysin O (ASO) titers by a latex reagent test kit; and IL-10 levels by an enzyme-linked immunosorbent assay (Biotech, China). Results: The female-to-male ratio was 3:1 in both the patient and control groups, with females composing 88% of patients and 70% of controls. The mean age was 37.44 ± 13.7 years in the patient group and 39.3 ± 11.4 years in the control group. Compared to controls, the mean serum levels of TSH and TPO were significantly higher in the patients group. Among HT patients, 23 (46%) tested positive for ASO, with a mean titer of 236.9 ± 35.7 U/mL, compared to 91.88 ± 24.1 U/mL in controls. The ROC curve analysis showed a cut-off value of 51.0 U/mL, with 100% sensitivity and 93% specificity. The mean serum IL-10 concentration was significantly lower in HT patients (0.188 ± 0.069 pg/mL), compared to healthy controls (0.96 ± 0.28 pg/mL). Conclusion: This study proved the concept that bacterial infections may cause autoimmune disorders by the fact that about half of the HT patients had positive ASO test findings, HT patients' decreased IL-10 levels suggest a potential immune regulatory deficiency that might aid in the disease's etiology.