Effects of contamination level of dioxins and related chemicals on thyroid hormone and immune response systems in patients with “Yusho”

Effects of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs) on thyroid hormone and immune response systems were examined in 16 Yusho patients at about 30 years after the outbreak of the Yusho accident. Their toxic equivalent (TEQ) levels in the blood were 27.8–1048.5 pg/g fat with the median level of 222.4 pg/g fat, which was about seven times higher than that of healthy Japanese people. Even at such high blood TEQ concentrations, they seemed not to affect the serum levels of thyroid hormones, thyroid stimulating hormone (TSH), immunoglobulins (A, G and M), autoantibodies (antinuclear antibody, rheumatoid and lupus erythematosus (LE) factors), and lymphocyte subsets in the blood. However, positive rates of rheumatoid factor were considered to increase in higher blood TEQ groups. This investigation was done using rather small number of Yusho patients, so further large-scale investigations are needed to get more conclusive findings concerning their effects on thyroid hormone and immune response systems.