Endocrine Abstracts

Soybean diet could involve in the development of goitre according to antithyroid effects of isoflavones. Isoflavones from Soybean could induce not only inhibition of thyroid peroxidase (TPO) catalyzed reactions but they are allergens for patients suffering from atopic or autoimmune diseases. Two hundred-sixty patients with thyroid autoimmunity (150 with Graves’ disease, 110 with Hashimoto’s thyroiditis) were investigated for the sensitization against Soybean. Allergen-specific IgE levels were measured by Western blot Allergy Screen panels and the levels of thyroid hormones (TSH, FT₄, FT₃) and anti-TPO, anti-Htg (thyroglobulin), TSH receptor (TRAK) antibodies were detected by immunoassay. The data were presented as mean±SE.

Allergic sensitization against Soybean was as follows: 24 cases in Graves’ disease and 16 cases in Hashimoto’s thyroiditis. Graves’ patients with Soybean allergy showed increased anti-TPO levels compared to patients who were negative for allergen (567.33±82.88 IU/ml vs 264.88±30.77 IU/ml, P<0.001). However, in patients with Soybean allergy, the elevation in anti-TPO levels was higher in hyperthyroid cases than in those without allergy (736.6±138.87 IU/ml (n=7) vs 296.15±50.81 IU/ml (n=41), P<0.011). Surprisingly, higher FT₃ (and FT₄) levels were demonstrated in sensitized hyperthyroid cases compared to nonsensitized ones (15.92±4.7 pg/ml vs 5.44±0.56 pg/ml, P<0.001 for FT₃ (and P<0.049 for FT₄)). The increase in anti-TPO levels for sensitized euthyroid Graves’ patients strongly associated with ophthalmopathy in comparison with nonsenzitized ones (669.98±162.38 IU/ml (n=6) vs 156.81±48.46 IU/ml (n=29), P<0.003).

In conclusion, the presence of Soybean allergen-specific IgE levels in thyroid autoimmunity could contribute to the elevation in anti-TPO levels for Th2 dominant Graves’ disease. The sensitization against Soybean may induce thyroid autoimmunity due to increased anti-TPO levels in disease susceptible patients.