Introduction Thyroid diseases occur more frequently in people exposed to ionising radiation (IR) for therapeutic purposes and to nuclear fallout, but relationship between occupational exposure to IR and thyroid pathologies still remains unclear.

Methods We ran a cross-section study to investigate whether healthcare workers routinely exposed to low-level IR had a higher prevalence of thyroid diseases. After giving written consent, 285 exposed workers (168 more exposed or ‘A category’ and 117 less exposed or ‘B category’) and 599 non-exposed were enrolled during routine examination at the Occupational Health Unite, programmed to monitor their health status. All subjects worked in the same university hospital and lived in the same geographical area of mild iodine deficiency. They were interviewed to fill in an anamnestic questionnaire (concerning to lifestyles, weariness habits and thyroid diseases risk factors) and underwent a physical examination, serum determination of fT3, fT4 and TSH, US neck scan and fine needle aspiration biopsy. Statistical analysis was performed using adjusted prevalence ratio (adPR) with software STATA 14.

Results Prevalence of thyroid diseases resulted statistically higher in exposed workers compared to controls (37% vs 30%, adPR 1.63; 95% CI: 1.34 to 1.97). In particular, thyroid nodularity prevalence in exposed group was about twice as higher than controls (28% vs 14%; adPR 2.67; 95% CI: 2.03 to 3.50). Any statistical association was found between IR exposure and malignant thyroid neoplasms (adPR 0.74; IC95% 0.18–3.02). At multivariate analysis, female gender, age and familial history of thyroid diseases were significant risk factors.

Discussion In our study, mildly IR exposed health workers had a statistically higher thyroid diseases prevalence than control group, even though no difference was found between A and B categories. Results likely are due to closer and more meticulous health surveillance program carried out in IR exposed workers, allowing to identify thyroid alterations earlier than non-exposed health staf.