Occupational heavy metal exposure and endocrine–metabolic biomarkers: a retrospective analysis of 34,595 screened individuals in Türkiye

BACKGROUND: Heavy metals and trace elements can act as endocrine-disrupting chemicals and have been linked to thyroid, glucose, lipid, and hepatic abnormalities. We aimed to explore associations between routinely measured metal concentrations and biochemical/endocrinological parameters in a large occupational screening dataset from Türkiye. METHODS: Records from 37,763 individuals evaluated at a national occupational and environmental diseases hospital between November 2021 and October 2023 were retrospectively reviewed; after prespecified exclusions, 34,595 unique participants were included. Metal measurements were performed in whole blood, serum, and urine samples as requested in routine surveillance; for each analyte, results were categorized as within or above the interpretive limit by the laboratory information system. Primary comparisons focused on arsenic, cadmium, lead, manganese, and zinc because of occupational relevance and sample size. Routine biochemistry, lipid profile, and thyroid function tests were extracted when available, and estimated glomerular filtration rate (eGFR, CKD‑EPI) was calculated. RESULTS: Among participants with available thyroid function tests (n = 9,956), thyroid dysfunction was observed in 14.3% (subclinical hypothyroidism 11.9%). Among participants with available fasting glucose and/or HbA1c data (n = 20,738), diabetes mellitus and prediabetes criteria were met in 12.8% and 10.0%, respectively. In univariable comparisons, several metals above the interpretive limit were associated with differences in metabolic biomarkers, including lower HDL with elevated cadmium, lower HDL/LDL with elevated manganese, and higher ALT/AST and triglycerides with elevated zinc. Elevated metal strata differed in age and sex distribution. After within-metal false discovery rate correction, only a limited subset of biomarker differences remained significant. CONCLUSION: Among tested participants, thyroid dysfunction and dysglycemia were observed, and selected metal measurements above interpretive limits were associated with lipid and liver enzyme patterns. Given the clinically driven testing and limited covariate data, these findings should be interpreted as exploratory surveillance signals rather than workforce-level prevalence estimates. Heavy metal exposure may exert endocrine-disrupting effects on workers in relevant industries, particularly on thyroid function and glycemic regulation, suggesting that periodic surveillance of these parameters is warranted in exposure-prone workforces.