Endocrine Abstracts

As a ubiquitously present metal, cadmium (Cd) represents a matter of great concern, especially considering its potential thyroid disrupting capacity. The study evaluated the connection between this environmentally relevant metal exposure and thyroid hormone levels. The DecodExpo study enrolled 425 participants (207 males and 218 females) with various disorders (236 participants) and healthy controls (189 participants). Collected blood samples were digested, and Cd levels were determined by flame atomic absorption method (AAS GTA 120 graphite tube atomizer and FAAS, Agilent technologies, Santa Clara, CA, USA). In contrast, thyroid-stimulating hormone (TSH) and free thyroxine (FT4) were measured in serum. The dose-response relationship between Cd in thyroid hormone disturbances was elucidated using a novel Benchmark dose (BMD) approach previously proposed as applicable to human data by the EFSA guidance. The Benchmark response (BMR) was set at 10% in the modeling procedure, expressed as an additional risk in% - an absolute change in response frequency divided by the non-affected fraction in the control population. PROAST 70.1 software was used for the calculations. Out of 435 participants, 76 had various thyroid disorders, and nearest-neighbor matching was performed to select the closest eligible healthy control unit paired with each patient with a thyroid disorder. Blood Cd levels were then compared between the two newly established groups: cases, and controls using the Man-Whitney-Wilcoxon test. The statistical analyses were performed using the R language and environment for statistical computing with additional packages. The BMD calculations revealed the following confidence interval for FT4 1.22-915 μg/l for men and 0.784-721 μg/l for women, while confidence intervals obtained for TSH were even wider. Although dose dependence was observed for Cd’s relationship with investigated hormones, the intervals calculated were wide, suggesting a high level of uncertainty. When comparing Cd levels in two established groups, the medium measured Cd blood level was 2.185 μg/l in cases while measured levels were 1.794 μg/l in corresponding controls, with no statistical differences observed between the Cd levels in these two groups. However, lower confidence intervals of BMD calculated for FT4 and TSH in both sexes were lower than the medium blood Cd levels obtained for the entire study, i.e., 1.8 μg/l (0.03-5.80 μg/l), which could suggest an additional risk of thyroid hormone disturbances due to Cd environmental exposure. Even though inconclusive, the results of this study urge the need for further investigations to elucidate the role of environmental exposure to Cd in thyroid disorders.