Since the incidence of cancer has increased over the years, adequate prevention programmes are needed. Thyroid cancer is one of the fastest growing cancer types in the world. In this study we performed a case-control study of 100 untreated patients with thyroid diseases (papillary thyroid cancer, follicular thyroid adenoma, and other thyroid diseases) and 100 control volunteers. Oxidative status differed among the two investigated groups. The patients' group had 1.60-fold higher concentrations of malondialdehyde and 1.26-fold higher concentrations of protein carbonyls. At the same time, the concentrations of glutathione and catalase activity were by 32% and 35% lower, respectively. A similar effect was observed for the cytogenetic status where higher comet assay tail intensity (1.84-fold) and the total numbers of chromosome aberrations (1.47-fold), micronuclei (2.32-fold), nucleoplasmic bridges (3.98-fold), and nuclear buds (2.34-fold) were detected. As for protein expression in thyroid tissue, 97.89% were positive for either B-Raf or Ret. Interestingly, the papillary thyroid cancer patients more frequently expressed B-Raf proteins compared to the follicular thyroid adenoma patients and patients with other thyroid diseases. Human biomonitoring studies enable a risk assessment of general population, such data could be used to identify risk subgroups.