Role of <i>Toxoplasma gondii</i> in thyroiditis in pregnant women

Abstract

Toxoplasmosis (acute and latent) is the most prevalent parasitic infection worldwide and can be associated with some problems in pregnant women. Thyroid diseases are the most common endocrine disorders secondary to diabetes among pregnant women. Previous studies proposed a relationship between latent еoxoplasmosis (LT) and autoimmune thyroiditis diseases (AITDs). This study intended to investigate the frequency and correlation between toxoplasmosis and AITD in pregnant women. In this cross-sectional study, the statistical population included 1248 pregnant women at the gestational age of 916 weeks and in Tehran. The Toxoplasma IgM and IgG tests were assessed with enzyme-linked immunosorbent assay (ELISA). The diagnostic criteria for toxoplasmosis were abnormal IgG and IgM titers. In addition, FT4, TPO Ab, and TSH were evaluated using enzyme-linked fluorescence immunoassay (ELFA). TPO Ab was used to distinguish thyroid patients with autoimmune origin from those with other thyroiditis diseases. The analysis showed no significant relationship between keeping a house cat and acute toxoplasmosis. Acute and latent toxoplasmosis represented 3.4% and 29.6%, respectively. The frequency of thyroid diseases was 18.8% (hypothyroidism 15.8% versus hyperthyroidism 3%). The frequency of autoimmune thyroiditis diseases (AITDs) was 5.5%, and 27.9% of subjects with latent toxoplasmosis (LT) had a thyroiditis disease, but 13.8% of pregnant women with LT had only AITD with a significant correlation (p 0.001). Results show that Toxoplasma IgG+ can increase the risk of AITD by 10.39-fold and a higher TPO Ab titer in people with LT. It seems Toxoplasma gondii may cause thyroiditis in pregnant women likely because antigenic similarity of Toxoplasma and thyroperoxidase leads to cross-reactivity in the immune system, potentially causing AITD. It might be said that the high prevalence of LT among pregnant women may have a potential role in the stimulation of the immune system to the development of autoimmune diseases, such as AITD. So future studies could be conducted with a focus on discovering molecular similarities between thyroperoxidase and Toxoplasma antigens.

Keywords

• latent toxoplasmosis
• acute toxoplasmosis
• autoimmune thyroiditis disease
• hypothyroidism
• hyperthyroidism