Association between Toxoplasma gondii infection and thyroid dysfunction: a case-control seroprevalence study

Abstract Background: The association between Toxoplasma gondii infection and thyroid disease has been poorly studied. Therefore, we sought to determine the association between T. gondii seropositivity and thyroid dysfunction. Methods: We performed an age- and gender-matched case-control study of 176 patients suffering from hypothyroidism (n=161) or hyperthyroidism (n=15) and 528 control subjects without these diseases in a public hospital in Durango City, Mexico. Anti- Toxoplasma IgG antibodies were determined in sera from cases and controls using a commercially available enzyme-linked immunoassay. Results: Anti- T. gondii IgG antibodies were found in 11 (6.3%) of 176 patients suffering from thyroid dysfunction and in 48 (9.1%) of 528 control subjects (OR=0.66; 95% CI: 0.33-1.31; P =0.23). Stratification by two groups of age (50 years and younger, and 51 year and older) showed that the youngest group of patients with thyroid dysfunction had a significantly lower seroprevalence of T. gondii infection than its age- and gender-matched control group (1/83: 1.2% vs 23/257: 8.6%; OR=0.12; 95% CI: 0.01-0.93; P =0.01). This stratification also showed that the youngest group of patients with hypothyroidism had a significantly lower seroprevalence of T. gondii infection than its age- and gender matched control group (0/75: 0% vs 21/233: 9.0%; P =0.003). Conclusions: Our results suggest that thyroid dysfunction is not associated with seropositivity to T. gondii in general; however, in young (50 years or less) patients, a negative association between infection and thyroid dysfunction and hypothyroidism was found. Further research to confirm this negative association is needed.