Aim: Environmental chemicals and heavy metals may alter thyroid hormone levels via several mechanisms, including disruption of iodine (I) transport, thyroid peroxi-dase, thyroid hormone-binding proteins, hepatic catabolism, deiodinases, and receptor binding. Our aim was to investigate the change in thyroid hormone levels in cadmium exposure. Material and Method: Painters, welders, miners, and smelters with an occupational exposure of more than 10 years, aged between 18-70 years, were divided into six groups according to whole blood cadmium levels (Group 1: 0-0.5 mu g/L; Group 2: 0.5-1 mu g/L; Group 3: 1-1.5 mu g/L; Group 4: 1.5-2 mu g/L; Group 5: 2-2.5 mu g/L; Group 6: > 2.5 mu g/L). Results: There was a positive correlation between cadmium and serum free thyroxine and triiodothyronine levels. There was a negative correlation between cadmium and serum alanine aminotransferase and vitamin B12 levels. Discussion: Cadmium exposure was found to lead to an increase in thyroid hormone levels.