Sex-specific effects of blood cadmium on thyroid hormones and thyroid function status: Korean nationwide cross-sectional study

Previous studies on blood cadmium (BCd) and changes in thyroid hormone levels are controversial. We investigated whether thyroid hormone levels and thyroid function status were associated with BCd according to sex in the Korean population. Our study included 1972 participants based on the 2013 Korea National Health and Nutrition Examination Survey (KNHANES) data. Participants whose thyroid-stimulating hormone (TSH) and free thyroxine (fT4) levels were altered physiologically or medically were excluded. Changes in TSH, fT4, and anti-thyroid peroxidase antibody (TPOAb) in men and women were analyzed by different characteristics: age, body mass index (BMI), smoking status, drinking status, BCd, and urine iodine-to-creatinine ratio (UI/Cre). Thyroid function status was classified as hypothyroidism, euthyroidism, and hyperthyroidism as defined by TSH and fT4 levels. Among the total participants, there was a negative correlation between BCd and fT4 (r = -0.067, p = 0.003). In men (n = 1057), fT4 levels decreased with increasing BCd quartile (p-for-trend = 0.002). After adjustment for age, BMI, smoking status, UI/Cre, and TPOAb, the association between BCd and hypothyroidism was significant in men (odds ratio = 1.813, p = 0.032) but not in women. These results suggest that cadmium accumulation is closely associated with thyroid dysfunction, and there is a difference in metabolic capacity according to sex.