Are ethnic differences, urinary iodine status, lead and cadmium exposure associated with thyroid autoimmunity and hypothyroid status? A cross-sectional study

Abstract

ObjectiveWe aimed to evaluate the effects of different ethnicities and potential environmental exposure on the prevalence of thyroid autoimmune status and hypothyroid status.DesignThe data were obtained from two cross-sectional studies.Participants2105 participants in Shanghai (Han) and 772 participants in Yunnan Honghe Prefecture (Han, Yi, Miao and Hani), aged 18–75 were enrolled.MethodsParticipants underwent several checkups, including urinary iodine concentration, blood lead (BPb) and blood cadmium (BCd), thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), thyroid stimulating hormone (TSH) as well as thyroid ultrasonography (US). Thyroid autoimmune status was defined as: antithyroid antibody positive (ATA+): TPOAb + or TgAb+; and ATA + and US+: TPOAb + or TgAb + together with characteristic US features.ResultsThe standardised prevalence of thyroid autoimmune positivity in Yunnan were higher than those in Shanghai (TPOAb+: 13.56% vs 8.27%, p<0.001; TgAb+: 9.28% vs 7.09%, p=0.045; ATA+: 16.96% vs 11.10%, p<0.001; ATA + and US+: 8.96% vs 6.64%, p=0.036). For urinary iodine-to-creatinine ratio (UI/Cr), compared with the level of 100.00–199.99 µg/g, the level of ≥300.00 µg/g had a 1.5-fold risk for ATA + and US+ (OR 1.455, p=0.041). The levels of 200.00–299.99 µg/g and ≥300.00 µg/g were positively associated with hypothyroid status (OR 1.509, p=0.002 and OR 1.338, p=0.043). Compared with the first quartiles, the fourth quartiles of BPb were positively associated with TPOAb+: (OR 1.637, p=0.006), ATA+ (OR 1.435, p=0.025), ATA + and US+ (OR 1.641, p=0.013), hypothyroid status (OR 1.467, p=0.013) and TSH levels (B 0.092, p=0.021). The fourth quartile of BCd was positively associated with the prevalence of ATA+ (OR 1.427, p=0.036).ConclusionsHigher levels of UI/Cr, BPb and BCd may be associated with thyroid autoimmunity and hypothyroid status.

Higher cadmium exposure was associated with sex-specific thyroid dysfunction: Consistent evidence from two independent cross-sectional studies based on urinary and blood cadmium measurements

“…As far as we know, only three previous studies have investigated the relationship between blood Cd exposure and thyroid function, two studies in China [ 22 , 23 ] and one study in Korea [ 24 ] consistently indicated that higher blood Cd was associated with higher risk of hypothyroidism, which was consistent with our findings in the study measuring urinary Cd concentrations (OR = 1.31). However, no significant association between blood Cd and hypothyroidism was observed in our study measuring blood Cd concentrations.…”

“…Moreover, an occupational Cd exposure study in Italy observed negative correlation between urinary Cd levels and free triiodothyronine (FT3) and free thyroxine (FT4) and positive correlation between urinary Cd and thyroid stimulating hormone (TSH) levels [19]. In addition, three studies have revealed a positive association between blood Cd and the risk of hypothyroid status [22][23][24]. It is of note that no study has explored the association between urinary Cd and thyroid dysfunction, and few studies have veri ed their conclusions by using both urinary Cd and blood Cd measures which re ect long-term exposure and short-term exposure, respectively [25].…”

The Relationship between Gastrointestinal Health, Micronutrient Concentrations, and Autoimmunity: A Focus on the Thyroid

“…Iodized salt helps prevent goiter and other thyroid conditions. However, supplemental dietary iodine has also been shown to increase the incidence of thyroid autoimmunity [22][23][24][25].…”