H. Pylori and Thyroid Hormone Levels: A Cross-sectional Study of Adults Participating in the National Health and Nutrition Examination Survey (NHANES III).

Purpose: Helicobacter pylori (H. Pylori) bacteria produce a strong inflammatory response in the body. It is hypothesized that strong immune responses to H.pylori can enhance systemic inflammation and produce an autoimmune response against the thyroid. Epidemiologic studies have assessed an association between H. pylori infection and autoimmune thyroid diseases, but with conflicting results and small study populations. Using a large, nationally representative US population, we investigated whether there is an observable association between H. pylori infection and levels of serum thyroid hormones (T4 and TSH) and anti-thyroglobulin antibodies. Methods: We analyzed cross-sectional data from the most recent National Health and Nutrition Examination Survey III (1988-1994) containing serum H. pylori and thyroid hormone levels. H. pylori infection status was determined by detection of antibodies. Chi-square and t-tests were used to assess differences by H. pylori status. Multivariable linear regression models were used to quantify the association between T4, TSH, and anti-thyroglobulin antibodies separately, while adjusting for age, sex, race/ethnicity, and BMI. Results: Among 5848 adults studied, the prevalence of H. Pylori infection was 32.8%. Mean T4, TSH, and anti-thyroglobulin antibodies differed by H.pylori status (p <0.05), but remained within the wide reference values. H. pylori infection was a significant predictor of higher T4 and anti-thyroglobulin antibodies, particularly in younger persons (<40 years of age). Conversely, a significant inverse association was observed for TSH. Similar differences were observed for the higher risk cytotoxin associated gene A H.pylori strain. Conclusions: Our findings suggest that H. pylori eradication may be important before abnormal thyroid levels can return to normal.