Abstract
BACKGROUND: Hypothyroidism is a relatively common endocrine disorder in human societies. Toxoplasmosis is also one of the most prevalent parasitic infectious diseases in mammalian hosts, causing opportunistic infections in healthy individuals and complications in immunocompromised patients. This infection is associated with several autoimmune diseases, including autoimmune thyroid disease. This case-control study aims to investigate latent T. gondii infection in patients with hypothyroidism who were registered with the Iranian National Registry Center for Toxoplasmosis (INRCT). METHODS: We conducted a case-control study involving 118 patients diagnosed with hypothyroidism and 100 subjects without hypothyroidism, serving as the control group. The Toxoplasma status was confirmed through the enzyme-linked immunosorbent assay (ELISA) for anti-Toxoplasma IgG and IgM antibodies. Levels of T3, T4, and thyroid-stimulating hormone (TSH) were measured using chemiluminescence immunoassay (CLIA). RESULTS: Anti-Toxoplasma IgG was detected in 69.5% of patients with hypothyroidism (82/118) and in 35.0% of the control group (35/100) (P < 0.05). However, all participants were negative for anti-Toxoplasma IgM. Based on the results from the multiple logistic regression (LR) model, and after adjusting for confounding factors, we found that the likelihood of hypothyroidism in subjects with Toxoplasma infection is 2.4 times greater than that of seronegative individuals. CONCLUSIONS: Our results demonstrate a significant association between latent T. gondii infection (IgG seropositivity) and hypothyroidism, supporting a potential role for chronic toxoplasmosis in thyroid dysfunction. These findings contribute to the understanding of potential links between chronic infections and endocrine dysfunction. However, the clinical utility of routine T. gondii screening in hypothyroid patients remains uncertain and warrants further investigation. CLINICAL TRIAL NUMBER: Not applicable.