Elevated Serum LPS in Newly Diagnosed Hashimoto’s Thyroiditis: A Case–Control Study in Bulgaria

<b>Background:</b> Hashimoto's thyroiditis (HT) is a prevalent autoimmune disorder, often diagnosed late due to its asymptomatic or nonspecific presentation. Emerging evidence suggests that gut-derived lipopolysaccharides (LPS) may contribute to autoimmune activation. <b>Objective</b>: The primary objective of this study was to assess circulating LPS concentrations and dietary patterns in patients with Hashimoto's thyroiditis compared to healthy controls. <b>Methods</b>: A hospital-based case-control study was conducted involving 105 HT patients and 25 healthy controls. Serum LPS concentrations, thyroid hormone profiles, and autoantibody levels were assessed. Dietary patterns were evaluated using the validated KomPAN questionnaire. <b>Results</b>: HT patients exhibited significantly higher serum LPS levels, particularly those with elevated anti-TPO and TRAB antibodies. A positive correlation was found between LPS and the fT3/fT4 ratio (<i>r</i> = 0.247, <i>p</i> = 0.006), and a negative correlation with fT4 (<i>r</i> = -0.314, <i>p</i> < 0.001). Dietary analysis revealed lower Pro-Healthy Diet Index scores in HT patients (3.94 vs. 5.34, <i>p</i> = 0.001), with increased consumption of processed foods and reduced intake of whole grains and oats. <b>Conclusions</b>: Elevated levels of lipopolysaccharides (LPS) and unhealthy dietary patterns may play a role in the development of thyroid autoimmunity. Taken together, these observations are consistent with a multifactorial model that potentially involves gut barrier dysfunction, endotoxemia, and nutritional factors in HT pathogenesis.